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Controlled Release Drug Delivery System (CDDS)By: Pharma Tips | Views: 21261 | Date: 29-Jun-2010

During the last two decades there has been remarkable increase in interest in controlled release drug

delivery system. This has been due to various factor viz. the prohibitive cost of developing new drug

entities, expiration of existing international patents, discovery of new polymeric materials suitable for

prolonging the drug release, and the improvement in therapeutic efficiency and safety achieved by these

delivery systems. Now-a-days the technology of controlled release is also being applied to veterin

Controlled Release Drug Delivery System (CDDS)

INTRODUCTION

CONTROLED RELEASE DRUG ADMINISTRATION:

During the last two decades there has been remarkable increase in interest in controlled release drug delivery

system. This has been due to various factor viz. the prohibitive cost of developing new drug entities, expiration

of existing international patents, discovery of new polymeric materials suitable for prolonging the drug release,

and the improvement in therapeutic efficiency and safety achieved by these delivery systems. Now-a-days the

technology of controlled release is also being applied to veterinary products.

Modified Release Dosage Forms2: According to the United States Pharmacopoeia the term 'modified release

dosage forms' is used to denote the dosage forms for which the drug release characteristics of time course

and/or location are chosen to accomplish therapeutic objectives not offered by the conventional dosage forms.

Two types of modified release dosage forms are recognised.

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1] Extended release dosage forms:

It is defined as the one that allows at least a two fold reduction in the dosing frequency as compared to that

of conventional dosage form.

2] Delayed release dosage forms:

It is defined as one that releases the drug at a time other than “immediately” after administration.

Rationale of controlled drug delivery3

The basic rationale for controlled drug delivery is to alter the pharmacokinetics and pharmacodynamics of

pharmacologically active moieties by using novel drug delivery system or by modifying the molecular structure

and /or physiological parameters inherent in a selected route of administration.

Terminology3,4 Different terminologies have been used for the new drug delivery system by different authors.

A] Controlled Action:

In this type of dosage forms it provides a prolonged duration of drug release with predictability and

reproducibility of drug release kinetics. In this case, the rate of drug absorption is equal to the rate of drug

removal from body.

2] Sustained Action:

In this type of dosage forms, a sufficient amount of drug is initially made available to the body to cause a

desired pharmacological response. The remaining fraction is released periodically and is required to maintain

the maximum initial pharmacological activity for some desirable period of time in excess of time expected from

usual single dose.

3] Prolonged Action:

These types of dosage form are designed in such a way that it release the drug over an extended period during

which pharmacological response is obtained but does not necessarily maintain the constant blood level.

4] Site specific and receptor release:

It refers to targeting of drug directly to a certain biological location.

Potential advantages and disadvantages of controlled release dosage forms

Advantages:4,5,6,7

i] Patient Compliance:

Lack of compliance is generally observed with long term treatment of chronic disease, as success of drug

therapy depends upon the ability of patient to comply with the regimen. Patient compliance is affected by a

combination of several factors, like awareness of disease process, patient faith in therapy, his understanding of

the need to adhere to a strict treatment schedule. Also the complexity of therapeutic regimens, the cost of

therapy and magnitude of local and or systemic side effect of the dosage form.

The problem of lack of patient compliance can be resolved to some extent by administering controlled release

drug delivery system.

ii] Reduced 'see- saw' fluctuation:

Administration of a drug in a conventional dosage form [except via intravenous infusion at a constant rate] often

results in 'see – saw' pattern of drug concentration in the systemic circulation and tissue compartments. The

magnitudes of these fluctuations depend on drug kinetics such as the rate of absorption, distribution, elimination

and dosing intervals. The 'see-saw' or 'peak and valley' pattern is more striking in case of drugs with biological

half lives of less than four hours, since prescribed dosing intervals are rarely less than four hours. A well

designed controlled release drug delivery system can significantly reduce the frequency of drug dosing and

also maintain a more steady drug concentration in blood circulation and target tissue cells.

iii] Reduced total dose:

Controlled release drug delivery systems have repeatedly been shown to use less amount of total drug to treat

a diseased condition. By reducing the total amount of drug, decrease in systemic or local side effects are

observed. This would also lead to greater economy.

iv] Improved efficiency in treatment:

Optimal therapy of a disease requires an efficient delivery of active drugs to the tissues, organs that need

treatment. Very often doses far in excess to those required in the cells have to be administered in order to

achieve the necessary therapeutically effective concentration. This unfortunately may lead to undesirable,

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toxicological and immunological effects in non-target tissue. A controlled release dosage forms leads to better

management of the acute or chronic disease condition.

Disadvantages:5,6,7

i) Dose dumping:

Dose dumping is a phenomenon where by relatively large quantities of drug in a controlled release formulation is

rapidly released, introducing potential toxic quantities of the drug into the systemic circulation. Dose dumping

can lead to fatalities in case of potent drug, which have a narrow therapeutic index e.g.

Phenobarbital.

ii) Less flexibility in accurate dose adjustment:

In conventional dosage forms, dose adjustments are much simpler e.g. tablet can be divided into two fractions.

In case of controlled release dosage forms, this appears to be much more complicated. Controlled release

property may get lost, if dosage form is fractured.

iii) Poor In Vitro – In Vivo correlation:

In controlled release dosage form, the rate of drug release is deliberately reduced to achieve drug release

possibly over a large region of gastrointestinal tract. Here the so called ‘Absorption window’ becomes important

and may give rise to unsatisfactory drug absorption in vivo despite excellent in-vitro release characteristics.

iv) Patient variation:

The time period required for absorption of drug released from the dosage form may vary among individuals. Co-

administration of other drugs, presence or absence of food and residence time in gastrointestinal tract is

different among patients. This also gives rise to variation in clinical response among the patient.

Criteria to be met by drug proposed to be formulated in controlled release dosage forms.5,6

a) Desirable half-life.

b) High therapeutic index

c) Small dose

d) Desirable absorption and solubility characteristics.

e) Desirable absorption window.

f) First past clearance.

a) Desirable half-life:

The half life of a drug is an index of its residence time in the body. If the drug has a short half life (less than 2

hours), the dosage form may contain a prohibitively large quantity of the drug. On the other hand, drug with

elimination half life of eight hours or more are sufficiently sustained in the body, when administered in

conventional dosage from, and controlled release drug delivery system is generally not necessary in such

cases. Ideally, the drug should have half-life of three to four hours.

b) High therapeutic index:

Drugs with low therapeutic index are unsuitable for incorporation in controlled release formulations. If the

system fails in the body, dose dumping may occur, leading to fatalities eg. Digitoxin.

c) Small dose:

If the dose of a drug in the conventional dosage form is high, its suitability as a candidate for controlled release

is seriously undetermined. This is chiefly because the size of a unit dose controlled release formulation would

become too big, to administer without difficulty.

d) Desirable absorption and solubility characteristics:

Absorption of poorly water soluble drug is often dissolution rate limited. Incorporating such compounds into

controlled release formulations is therefore unrealistic and may reduce overall absorption efficiency.

e) Desirable absorption window:

Certain drugs when administered orally are absorbed only from a specific part of gastrointestinal tract. This

part is referred to as the ‘absorption window’. Drugs exhibiting an absorption window like fluorouracil, thiazide

diuretics, if formulated as controlled release dosage form are unsuitable.

f) First pass clearance:

As discussed earlier in disadvantages of controlled delivery system, delivery of the drug to the body in desired

concentrations is seriously hampered in case of drugs undergoing extensive hepatic first pass metabolism,

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when administered in controlled release forms.

DESIGN AND FORMULATION OF ORAL CONTROLLED RELEASE DRUG DELIVERY SYSTEM AND

THE FACTORS AFFECTING THEREOF:7,8,9,10

The oral route of administration is the most preferred route due to flexibility in dosage form, design and patient

compliance. But here one has to take into consideration, the various pH that the dosage form would encounter

during its transit, the gastrointestinal motility, the enzyme system and its influence on the drug and the dosage

form. The majority of oral controlled release systems rely on dissolution, diffusion or a combination of both

mechanisms, to generate slow release of drug to the gastrointestinal milieu.

Theoretically and desirably a controlled release delivery device, should release the drug by a zero-order

process which would result in a blood-level time profile similar to that after intravenous constant rate infusion.

Controlled (zero-order) drug release can be schematically illustrated as follows:7

Plasma drug concentration-profiles for conventional tablet or capsule formulation, a sustained release

formulation, and a zero order controlled release formulation.

Controlled (zero-order) drug release has been attempted to be achieved, by following classes of controlled

drug delivery system.8

A) Diffusion controlled system.

i) Reservoir type.

ii) Matrix type

B) Dissolution controlled system.

i) Reservoir type.

ii) Matrix type

C) Methods using Ion-exchange.

D) Methods using osmotic pressure.

E) pH independent formulations.

F) Altered density formulations.

A] Diffusion controlled system:

Basically diffusion process shows the movement of drug molecules from a region of a higher concentration to

one of lower concentration. The flux of the drug J (in amount / area -time), across a membrane in the direction of

decreasing concentration is given by Fick’s law.

J= - D dc/dx.

D = diffusion coefficient in area/ time

dc/dx = change of concentration 'c' with distance 'x'

In common form, when a water insoluble membrane encloses a core of drug, it must diffuse through the

membrane, the drug release rate dm/ dt is given by,

dm/ dt= ADK C/L

Where A = area

K = Partition coefficient of drug between the membrane and drug core

L= diffusion path length [i.e. thickness of coat]

c= concentration difference across the membrane.

1] Reservoir type:

Schematic representation of diffusion controlled drug release: reservoir system.

In the system, a water insoluble polymeric material encases a core of drug. Drug will partition into the

membrane and exchange with the fluid surrounding the particle or tablet .Additional drug will enter the polymer,

diffuse to the periphery and exchange with the surrounding media.

Characterization

Description: Drug core surrounded by polymer membrane which controls release rate.

Advantages: Zero order delivery is possible, release rates variable with polymer type.

Disadvantages: System must be physically removed from implant sites. Difficult to deliver high molecular

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weight compound, generally increased cost per dosage unit, potential toxicity if system fails.

Products:

Products Drug Manufacturer

Duotrate Pentaerythritol tetranitrate Marion

Histospan Chlorpheniramine maleate USV

Methascopolamine nitrate

Nitrospan Nitroglycerin USV

Capsules

Bronkodyl Theophylline Breon

ii] Matrix type:

A solid drug is dispersed in an insoluble matrix and the rate of release of drug is dependent on the rate of drug

diffusion and not on the rate of solid dissolution.

Higuchi has derived the appropriate equation for drug release for this system,

Q = D / T [2 A – Cs] Cst ½

Where;

Q = weight in gms of drug released per unit area of surface at time t

D = Diffusion coefficient of drug in the release medium

= porosity of the matrix

Cs = solubility of drug in release medium

T= Tortuosity of the matrix

A = concentration of drug in the tablet, as gm/ ml

Characterization

Description: Homogenous dispersion of solid drug in a polymer mixture.

Advantages: Easier to produce than reservoir or encapsulated devices, can deliver high molecular weight

compounds.

Disadvantages: Cannot provide zero order release, removal of remaining matrix is necessary for implanted

system.

Products:

Products Drug Manufacturer

Desowyn Methamphetamine hydrochloride Abott

Procaine SR Procainamide hydrochloride Parke Davis

tabs

Priscoline Tolazoline hydrochloride CIBA

Schematic representation of diffusion controlled drug release: matrix system.

A third possible diffusional mechanism is the system where a partially soluble membrane encloses a drug core.

Dissolution of part of membrane allows for diffusion of the constrained drug through pores in the polymer coat.

The release rate can be given by following equation:-

Release rate = AD / L = [ C1- C2 ]

Where,

A = Area

D = diffusion coefficient

C1 = Drug concentration in the core

C2 = Drug concentration in the surrounding medium

L = diffusional path length

Thus diffusion controlled products are based on two approaches the first approach entails placement of the

drug in an insoluble matrix of some sort. The eluting medium penetrates the matrix and drug diffuses out of the

matrix to the surrounding pool for ultimate absorption. The second approach involves enclosing the drug particle

with a polymer coat. In this case the portion of the drug which has dissolved in the polymer coat diffuses

through an unstirred film of liquid into the surrounding fluid.

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B] Dissolution controlled systems:

A drug with a slow dissolution rate is inherently sustained and for those drugs with high water solubility, one can

decrease dissolution through appropriate salt or derivative formation. These systems are most commonly

employed in the production of enteric coated dosage forms. To protect the stomach from the effects of drugs

such as Aspirin, a coating that dissolves in natural or alkaline media is used. This inhibits release of drug from

the device until it reaches the higher pH of the intestine. In most cases, enteric coated dosage forms are not

truly sustaining in nature, but serve as a useful function in directing release of the drug to a special site. The

same approach can be employed for compounds that are degraded by the harsh conditions found in the gastric

region.

i) Reservoir type:

Drug is coated with a given thickness coating, which is slowly dissolved in the contents of gastrointestinal tract.

By alternating layers of drug with the rate controlling coats as shown in figure, a pulsed delivery can be

achieved. If the outer layer is quickly releasing bolus dose of the drug, initial levels of the drug in the body can

be quickly established with pulsed intervals. Although this is not a true controlled release system, the biological

effects can be similar. An alternative method is to administer the drug as group of beads that have coating of

different thickness. This is shown in figure. Since the beads have different coating thickness, their release

occurs in a progressive manner.

Those with the thinnest layers will provide the initial dose. The maintenance of drug levels at late times will be

achieved from those with thicker coating. This is the principle of the spansule capsule. Cellulose nitrate

phthalate was synthesized and used as an enteric coating agent for acetyl salicylic acid tablets.

Products:

Product Drug Manufacturer

Spansule capsule Amphetamine sulphate Smith kline

and French

Sequel capsule Acetazolamide Lederle

Diamox Ferrous fumarate

Docusate sodium

Matrix type: The more common type of dissolution controlled dosage form as shown in figure. It can be either a

drug impregnated sphere or a drug impregnated tablet, which will be subjected to slow erosion.

Products:

Product Drug Manufacturer

Timespan raniacol Nicotinyl alcohol Roche

extended tablets

Dimetane Brompheniramine Robins

maleate

Two types of dissolution- controlled pulsed delivery systems:

a] Single bead – type device with alternating drug and rate- controlling layer.

b] Beads containing drug with differing thickness of dissolving coats.

C] Methods using lon Exchange:

It is based on the formation of drug resin complex formed when a ionic solution is kept in contact with ionic

resins. The drug from these complex gets exchanged in gastrointestinal tract and released with excess of Na+

and Cl- present in gastrointestinal tract

Resin + - Drug - + x- goes to resin + x- + Drug-

Where x- is cl- conversely

Resin - - drug+ + Y +goes resin – Y+ + Drug

Where Y +is Na +

These systems generally utilize resin compounds of water insoluble cross – linked polymer. They contain salt –

forming functional group in repeating positions on the polymer chain. The rate of drug diffusion out of the resin is

controlled by the area of diffusion, diffusional path length and rigidity of the resin which is function of the amount

of cross linking agent used to prepare resins .The release rate can be further controlled by coating the drug

resin complex by microencapsulation process.15 The resins used include Amberlite Indion, polysterol resins

and others.

D] Methods using osmotic pressure:9

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A semi permeable membrane is placed around a tablet, particle or drug solution that allows transport of water

into the tablet with eventual pumping of drug solution out of the tablet through a small delivery aperture in tablet

coating.

Characterization

Description: Drug surrounded by semi permeable membrane and release governed by osmotic pressure.

Advantages: Zero order release rates are obtainable. Reformulation is not required for different drugs. Release

of drug is independent on the environment of the system.

Disadvantages: System can be much more expensive than conventional counterparts. Quality control is more

extensive than most conventional tablets.

Two types of osmotically controlled systems are:-

Type A contains an osmotic core with drug

Type B contains the drug in flexible bag with osmotic core surrounding.

E] pH– Independent formulations:8,12

The gastrointestinal tract present some unusual features for the oral route of drug administration with relatively

brief transit time through the gastrointestinal tract, which constraint the length of prolongation, further the

chemical environment throughout the length of gastrointestinal tract is constraint on dosage form design. Since

most drugs are either weak acids or weak bases, the release from sustained release formulations is pH

dependent. However, buffers such as salts of amino acids, citric acid, phthalic acid phosphoric acid or tartaric

acid can be added to the formulation, to help to maintain a constant pH thereby rendering pH independent drug

release. A buffered controlled release formulation is prepared by mixing a basic or acidic drug with one or more

buffering agent, granulating with appropriate pharmaceutical excipients and coating with gastrointestinal fluid

permeable film forming polymer. When gastrointestinal fluid permeates through the membrane, the buffering

agents adjust the fluid inside to suitable constant pH thereby rendering a constant rate of drug release e.g.

propoxyphene in a buffered controlled release formulation, which significantly increase reproducibility.12

F] Altered density formulations:3

It is reasonable to expect that unless a delivery system remains in the vicinity of the absorption site until most, if

not all of its drug contents is released, it would have limited utility. To this end, several approaches have been

developed to prolong the residence time of drug delivery system in the gastrointestinal tract.

High density approach

In this approach the density of the pellets must exceed that of normal stomach content and should therefore be

at least 1-4gm/cm3.

Low density approach:

Globular shells which have an apparent density lower than that of gastric fluid can be used as a carrier of drug

for sustained release purpose.

Factors Influencing Design of Controlled Release Dosage Forms:3,8,9

The therapeutic efficacy of drug under clinical conditions is not simply a function of its intrinsic pharmacological

activity but also depends upon the path of the drug molecule from the site of administration to the target site.

Different conditions encountered by the drug molecule while traversing the path of distribution may alter either

the effectiveness of the drug or affect the amount of the drug reaching the receptor site.

A] Pharmaceutics: This refers to the development/manufacturing of an efficient delivery system in which the

drug has maximum physiological stability and optimum bioavailability.

B] Biopharmaceutics/ pharmacokinetics: This involves the study of absorption, distribution, metabolism and

excretion of the drug, before and after reaching the target site and evaluation of the relationship between

delivery system and therapeutic response.

C] Pharmacodynamics/ Clinical Pharmacology:It is the study of the mechanism of action and clinical efficacy of

a drug administered in dosage form in terms of onset, intensity and duration of pharmacological activity.

Drug properties influencing the design of sustained or controlled release drug delivery system are classified as:

1] Physicochemical properties of the drug

These include dose size, aqueous solubility, protein binding, molecular size, drug stability and partition

coefficients.

2] Biological factors

These include absorption, distribution, metabolism, duration of action, margin of safety, side effects of drug,

disease state and circadian rhythm.

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Methods to achieve oral controlled drug delivery:8

There are various methods employed for the fabrication of oral controlled release delivery systems. Ritschel

has given a detailed report of these techniques. These are as follows.

a. Hydrophilic matrix

b. Plastic matrix

c. Barrier resin beads

d. Fat embedment

e. Repeat action

f. Ion exchange resin

g. Soft gelatin depot capsules

h. Drug complexes

In the following discussion, controlled release dosage form using method of matrix is discussed.

Matrix devices:

Historically, the most popular drug delivery system has been the matrix because of its low cost and ease of

fabrication. Methods of altering the kinetics of drug release from the inherent first order behavior especially to

achieve a constant rate of drug release from matrix devices have involved several factors.

Requirements of matrix materials:

The matrix materials must comply with the following conditions,

1. They must be completely inert and non- reactive with the drug and additives in the tablet.

2. They must be able to form a stable and strong matrices when compressed either directly or more often as

granules prepared by the addition of a binding agent.

3. They must be non-toxic.

Hydrophilic matrix system:

Carboxymethylcellulose sodium, hydroxymethyl cellulose, polyethylene oxide, polyvinyl-107, molidones and

natural gums can be used as matrix materials. The matrix may be tableted by direct compression of the blend of

active ingredient and certain hydrophilic carriers or from a wet granulation containing the drug and hydrophilic

matrix material.

Upon immersion in water the hydrophilic matrix quickly forms a gel layer around the tablet. Drug release is

controlled by a gel diffusional barrier and /or tablet erosion.

Evaluation of controlled release Tablets:

Before marketing a controlled release product, it is must to assure the strength, safety, stability and reliability of

a product by forming in-vitro and in-vivo analysis and correlation between the two. Various authors have

discussed the evaluating parameters and procedures for controlled release formulations.

1. In – Vitro Methods

These are:-

a. Beaker method

b. Rotating disc method

c. Rotating Bottle method

d. Rotating Basket method

e. Stationary Basket Method

f. Oscillating tube method

g. Dialysis method

h. USP dissolution method.

2. In–Vivo Methods

Once the satisfactory in-vitro profile is achieved, it becomes necessary to conduct in-vivo evaluation and

establish in-vitro in-vivo correlation. The various in-vivo evaluation methods are:-

a. Clinical response

b. Blood level data

c. Urinary excretion studies

d. Nutritional studies.

e. Toxicity studies

f. Radioactive tracer techniques

3.Stability Studies :6,14

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Adequate stability data of the drug and its dosage form is essential to ensure the strength, safety, identity,

quality, purity and in-vitro in-vivo release rates, that they claim to have at the time of use. A controlled release

product should release a predetermined amount of the drug at specified time intervals, which should not change

on storage. Any considerable deviation from the appropriate release would render the controlled release product

useless. The in-vitro and in-vivo release rates of controlled release product may be altered by atmospheric or

accelerated conditions such as temperature & humidity.

The stability programmes of a controlled release product include storage at both nominal and accelerated

conditions such as temperature & humidity to ensure that the product will withstand these conditions.

In vitro- In vivo Correlations:6,13

The requirement of establishing good in-vitro in-vivo correlation in the development of controlled release

delivery systems is self evident. To make a meaningful in-vitro in-vivo correlation one has to consider not only

the pharmaceutical aspect of controlled release drug delivery system but also the biopharmaceutics and

pharmacokinetics of the therapeutic agent in the body after its release from the drug delivery system and also

the pharmacodynamics of therapeutic agent at the site of drug action.

A simple in vitro-in vitro relationship can be established by conducting in-vitro and in-vivo evaluations of a

potential drug delivery system simultaneously to study and compare the mechanism and rate profiles of

controlled drug release. When the in-vivo drug release mechanism is proven to be in good agreement with that

observed in the in-vitro drug release studies, then in-vitro in-vivo correlation factor is derived. For capsule type

drug delivery system the factor can be represented as:

(Q/t) in-vivo

Q=

(Q/t) in-vitro

Where Q/t = Rate of release

‘Q’ values are dependent profiles of drug delivery systems. upon the sites of administration and environmental

conditions to which the animals are exposed during treatment (study). The above relationship can be used for

optimization of controlled release Levy has classified in-vivo – in-vitro correlation in to:

a] Pharmacological correlations based on clinical observations;

b] Semi-quantitative correlations based on blood levels or urinary

excretion data;

c] Quantitative correlation arising from absorption kinetics. While most of the published correlations are of semi-

quantitative nature, the most valuable are those based on absorption kinetics.

Bioavailability Testing: 6,15

Bioavailability is generally defined as the rate and extent of absorption of unchanged drug from its site of

application to the general circulation. Bioavailability is defined in terms of a specific drug moiety, usually active

therapeutic entity, which may be the unchanged drug or as with prodrug, for instance, a metabolite. In contrast,

the term "absorption" often refers to net transport of drug related mass from its site of application into the body.

Hence, a compound may be completely absorbed but only partially bioavailable as would occur, when low

bioavailability is caused by incomplete absorption. Pharmaceutical optimization of the dosage form may be

warranted to improve absorption characteristics of the drug and thereby also its bioavailability. Bioavailability

studies are ordinarily single dose comparisons of tested drug product in normal adults in a fasting state. A

crossover design, in which all subjects receive both, the product and reference material on different days is

preferred. Guidelines for clinical testing have been published for multiple dose studies. Correlation of

pharmacological activity or clinical evidence of therapeutic effectiveness with bioavailability may be necessary

to validate the single significance of controlled release claims. While single dose studies are usually sufficient to

establish the validity of sustained release dosage form design; multiple dose studies are required to establish

optimum dosing regimen. They are also required when difference may exist in the rate but not the extent of

absorption. When there is excessive subject to subject variation or when the observed blood levels after a

single dose are too low to be measured accurately. A sufficient number of doses must be administered to attain

steady state blood levels. According to an extensive study of sustained release Theophylline products; for

example, encapsulated forms showed less peaking during multiple dosing and therefore better control of blood

level within the desired limits.

Regulatory Requirements: 15,16

In India, the controlled release drug products in legal sense are considered to be "New Drugs" according to

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schedule 'Y' of Drugs and Cosmetic Act and Rules. The guidelines given under Drugs and Cosmetic Act 1940,

and Rules thereunder, 1945, under the schedule 'Y' inserted by notification no. GSR 944 (E), dated September

29, 1988, gives the data required to be submitted with application for permission to market a new drug.

The data is as follows:

1) Introduction: a brief description of the drug, the therapeutic class in which it belongs.

2) Chemical and pharmaceutical information.

a) Chemical name: Code number or name if any, non-proprietary or generic name, structure, physicochemical

properties.

b) Dosage form and its composition.

c) Specification of active and inactive ingredients.

d) Tests for identification of active ingredients and method of its assay.

e) Outline of the method of manufacture of the active ingredient.

f) Stability data.

3) Animal Pharmacology

4) Animal toxicology

a) Summary

b) Acute toxicity

c) Long term toxicity

d) Reproduction studies

e) Local toxicity

f) Mutagenicity and carcinogenicity

5) Human clinical pharmacology (Phase I)

a) General pharmacological effects

b) Pharmacokinetics

6) Exploratory clinical trials

a) Summary

b) Investigator wise reports

7) Confirmatory clinical trials

a) Summary

b) Investigator wise report

8) Special studies

a) Summary

b) Bioavailability and dissolution studies

c) Investigator wise report

9) Regulatory status in other countries

a) Countries where,

i) Marketed

ii) Approved

iii) Under trial, with phase

iv) Withdrawn, reasons

b) Restriction in use, if any, in countries where marketed/approved.

c) Free sale certificate from country or origin.

10) Marketing information

a) Proposed product monograph

b) Drafts of labels and cartons

RECENT WORK REVIEW ON CONTROL DRUG RELEASE SYSTEM:

LEE et al.,(1999)17prepared A hydroxypropyl methylcellulose (HPMC) matrix tablet containing melatonin (MT)

was formulated as a function of HPMC viscosity, drug loading, type and amount of disintegrant, lubricant and

glidant, and aqueous polymeric coating level and was compared with two commercial products. The release

characteristics of the HPMC matrix tablet were investigated in the gastric fluid for 2 hr followed by study in

intestinal fluid. The surface morphology of an uncoated HPMC matrix tablet using scanning electron microscopy

(SEM) was crude, showing aggregated particles and rough crystals or pores, but it became smoother as the

coating levels increased. As the HPMC polymer viscosity increased, the release rate had a tendency to

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decrease. As the drug loadings increased, the release rate slightly decreased. When Polyplasdone XL,

Primojel, and Ac-Di-Sol, except Avicel, were incorporated in the HPMC matrix tablet, the release rate was

markedly increased. There was no significant difference in release profiles when a mixture of lubricants and

glidants (magnesium stearate, talc, and Cab-O-Sil), except for magnesium stearate alone, was incorporated

into low and high viscosity grade HPMC matrix tablets. As the coating level increased, the release rate

gradually decreased, giving an increased lag time. The sustained-release HPMC matrix tablet with optimizing

formulations may provide an alternative for oral controlled delivery of MT and be helpful in the future treatment of

circadian rhythmic disorders

OCHOA L et al.,(2008)18 prepare theophylline sustained release matrix tablets based on the combination of

hydroxypropyl methylcellulose (HPMC K4M and K100M) and different meltable binders by melt granulation in a

high-shear mixer. METHODS: Dissolution profiles of each formulation were compared to those of TheoDur 200

mg tablets and the mean dissolution time (MDT) and similarity factor (f2 factor) were calculated. The matrices

swelling behavior was investigated by texture analysis. RESULTS: The results obtained show that the type of

excipient influenced the drug release rate. In particular, the dissolution rate was delayed when lipophilic binders

were used and only formulations containing Gelucire 50/13 or PEG 6000 with HPMC K4M had a profile similar

to the commercial formulation. The release mechanism of theophylline from the formulations was described by

Peppas's equation showing a non-Fickian release mechanism. The investigation of matrices swelling behavior

showed that the gel layer thickness increased continuously over the time period studied. Moreover, a

correlation between gel layer thickness and strength with the percentage released was found.

CONCLUSIONS: These results suggest that melt granulation could be an easy and fast method to formulate

sustained release tablets.

DONG W et al.,(2005)19 developed Enteric microparticles were prepared by a novel microencapsulation

method in order to improve the oral bioavailability of lipophilic drugs. This method involved the addition of an

aqueous polymer solution to an organic enteric polymer solution containing lipophilic drugs. In contrast to

classical coacervation microencapsulation methods, the drugs were initially also dissolved and not dispersed in

the organic polymer solution. The hydrophilic polymer (hydroxypropyl methylcellulose (HPMC), hydroxypropyl

cellulose (HPC) and Poloxamer 407) was dissolved in the aqueous phase and acted as a stabilizer for the

coacervate droplets, preventing their coalescence and leading to the formation of enteric microparticles. The

size of the enteric microparticles decreased with higher concentrations of the hydrophilic polymers, a higher pH

of the aqueous polymer solution, a higher content of carboxyl groups of the enteric polymer and with better

polymer solvents. Amide-containing lipophilic drugs, such as carbamazepine, lidocaine and cyclosporine A,

were successfully encapsulated in the enteric microparticles in a non-crystalline state and were physically

stable for 5 months. The high solubility of carbamazepine in the enteric polymer (>30%, w/w), a high partition

coefficient between polymer-rich/-poor regions and strong drug/polymer interactions contributed to the high drug

encapsulation efficiency (90%, w/w). In contrast, carboxyl-containing drugs (indomethacin, ibuprofen) and

hydroxyl-containing drug (17beta-estradiol hemihydrate) crystallized inside or outside the polymeric matrix due

to their low solubility in the enteric polymer.

DI COLO et al.,(2007)20 prepared a system able to sustain release of high MF-HCl doses in compliance with

the above requirement. Matrices (6 mm diameter; 50 mg weight) comprising varying drug-Precirol ATO 5 ratios

were prepared by compression. The matrix containing 70% drug was coated on one face with Eudragit L100-

55. Drug release to simulated gastric (SGF), jejunal (SJF) and ileal (SIF) fluids in sequence was studied using a

modified USP rotating basket method. Release depended on drug load whereas it was independent of

dissolution medium pH and hydrodynamics. Release kinetics were of radical t type and were determined by

drug diffusion in aqueous pores created in the matrix by drug dissolution. An equation correlating rate-

determining factors was developed, whereby the release pattern could be optimized. The half-coated matrix

started release in SGF and completed it in SJF. The half-coated matrix, synchronizing drug release and matrix

transit across the small intestine, may improve drug bioavailability and reduce side effects.

Bailey CJ et al .,(2008)21 Combined of two or more oral agents with different mechanisms of action are often

used for the management of hyperglycaemia in type 2 diabetes. While these combinations have customarily

been taken as separate tablets, several fixed-dose single tablet combinations are now available. These are

based on bioequivalence with the separate tablets, giving similar efficacy to the separate tablets and

necessitating the same cautions and contraindications that apply to each active component. Fixed-dose

combinations can offer convenience, reduce the pill burden and simplify administration regimens for the patient.

They increase patient adherence compared with equivalent combinations of separate tablets, and this is

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associated with some improvements in glycaemic control. Presently available antidiabetic fixed-dose

combinations include metformin combined with a sulphonylurea, thiazolidinedione, dipeptidylpeptidase-4 inhibitor

or meglitinide as well as thiazolidinedione-sulphonylurea combinations, each at a range of dosage strengths to

facilitate titration. Anticipated future expansion of multiple drug regimens for diabetes management is likely to

increase the use of fixed-dose single tablet combinations.

LEE BJ et al.,(2008)22 A dual drug-loaded hydroxypropylmethylcellulose (HPMC) matrix tablet simultaneously

containing drug in inner tablet core and outer coated layer was formulated using drug-containing aqueous-based

polymeric Eudragit RS30D dispersions. Effects of coating levels, drug loadings in outer layers, amount and type

of five plasticizers and talc concentration on the release characteristics were evaluated on the characteristics in

simulated gastric fluid for 2 h followed by a study in intestinal fluids. Melatonin (MT) was selected as a model

drug. The surface morphology of dual drug-loaded HPMC tablets using scanning electron microscope (SEM)

was smooth, showing the distinct coated layer with about 75-microm coating thickness at the 15% coating

level.. The time for the first linear release was also advanced. However, the biphasic release pattern was not

changed. The biphasic release profiles of dual drug-loaded HPMC matrix tablet were highly modified, depending

on the amount and type of five plasticizers. Talc (10-30%) in coating dispersion as an anti-sticking material did

not affect the release profiles. The current dual drug-loaded HPMC matrix tablet, showing biphasic release

profiles may provide an alternative to deliver drugs with circadian rhythmic behaviors in the body but needs to

be further validated in future in human studies. The dual drug-loaded coating method is also interesting for the

modified release of poorly water-soluble drugs because solubilizers and other additives can be added in drug-

containing polymeric coating dispersions.

TALUKDER MM et al.,(2008)23 prepared a swelling matrix core containing pectin, hydroxypropyl

methylcellulose (HPMC), microcrystalline cellulose and 5-aminosalicylic acid was developed. This was

subjected to a dual coating operation: an inner pH-sensitive enteric and an outer semi-permeable membrane

coat with a pore former. In-vitro dissolution studies were carried out in USP apparatus-I using sequential pH

media. The first 2 h of dissolution studies were done in HCl buffer at pH 1.5, the next 2 h in pH 5.5 and, finally, in

phosphate buffer at pH 6.8 with and without pectinolytic enzyme present. Less than 2% drug was released in

the first 6 h and about 90% released in the following 12 h in a controlled manner. The stability studies of the

coated systems were performed for 90 days under various conditions and it was found that drug release was

not adversely affected. Results indicate that this delivery system has potential for site-specific delivery of drugs

to the colon irrespective of transit time and rapid changes in the proximal pH of the gastrointestinal tract.

CONTOAR SL et al., (2004)24 to investigate the effectiveness of an ethylcellulose (EC) bead matrix and

different film-coating polymers in delaying drug release from compacted multiparticulate systems. Formulations

containing theophylline or cimetidine granulated with Eudragit(R) RS 30D were developed and beads were

produced by extrusion-spheronization. Drug beads were coated using 15% wt/wt Surelease(R) or Eudragit(R)

NE 30D and were evaluated for true density, particle size, and sphericity. Lipid-based placebo beads and drug

beads were blended together and compacted on an instrumented Stokes B2 rotary tablet press. Although

placebo beads were significantly less spherical, their true density of 1.21 g/cm(3) and size of 855 mum were

quite close to Surelease(R)-coated drug beads. Although modified release profiles >8 h were achievable in

tablets for both drugs using either coating polymer, Surelease(R)-coated theophylline beads released drug

fastest overall. This is likely because of the increased solubility of theophylline and the intrinsic properties of the

Surelease(R) films. Furthermore, the lipid-based placebos served as effective cushioning agents by protecting

coating integrity of drug beads under a number of different conditions while tableting.

Vueba ML et al.,(2006)25 study of different ketoprofen:excipient formulations, in order to determine the effect of

the polymer substitution and type of diluent on the drug-release mechanism. Substituted cellulose-

methylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose were used as polymers, while

lactose monohydrate and beta-cyclodextrin were tested as diluents. Distinct test formulations were prepared,

containing 57.14% of ketoprofen, 20.00% of polymer, 20.29% of diluent, and 1.71% of talc/0.86% of magnesium

stearate as lubricants. The tablets were tested for their drug content, weight variation, hardness, thickness,

tensile strength, friability, swelling and release ratio. Polymers MC25 and HPC were found not to be appropriate

for the preparation of modified release ketoprofen hydrophilic matrix tablets, while HPMC K15M and K100M

showed to be advantageous. The analysis of the release profiles in the light of distinct kinetic models (zero-

order, first-order, Higuchi and Korsmeyer-Peppas) led to the conclusion that the type of polymer did not

influence the release mechanism of the drug. The mean dissolution time (MDT) was determined, the highest

MDT value being obtained for HPMC formulations. Moreover, the drug-release process was found to be slightly

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influenced by the type of diluent, either lactose or beta-cyclodextrin

Corti G et al., (2007)26 develop a MH sustained-release formulation in compliance with these requirements. The

strategy proposed is based on direct-compressed matrix tablets consisting of a combination of MH with the

hydrophobic triacetyl-beta-cyclodextrin (TAbetaCD), dispersed in a polymeric material. Different polymers were

tested as excipients, i.e. hydroxypropylmethylcellulose, xanthan gum, chitosan, ethylcellulose, Eudragit L100-

55, and Precirol. Compatibility among the formulation components was assessed by DSC analysis. All the

tablets were examined for drug release pattern in simulated gastric and jejunal fluids used in sequence to mimic

the GI transit. Release studies demonstrated that blends of a hydrophobic swelling polymer

(hydroxypropylmethylcellulose or chitosan) with a pH-dependent one (Eudragit L100-55) were more useful than

single polymers in controlling drug release. Moreover, the main role played by the MH-TAbetaCD system

preparation method (i.e. grinding or spray-drying) in determining the behaviour of the final formulation was

evidenced. In fact, for a given matrix-tablet composition, different sustained-release effects were obtained by

varying the relative amounts of MH-TAbetaCD as ground or spray-dried product. In particular, the 1:1 (w/w)

blend of such systems, dispersed in a Eudragit-chitosan polymeric matrix, fully achieved the prefixed goal,

giving about 30% released drug after 2h at gastric pH, and overcoming 90% released drug within the

subsequent 3h in jejunal fluid.

Kapat et al., (2004)27 this work has focused on the effects of different hydroxypropylmethylcellulose (HPMC)

types and HPMC :direct tabletting agent (DC-agent) ratio on Verapamil Hydrochloride (VRP HCl) release from

monolayered and three-layered matrix tablets. Investigated polymers were Methocel K100LV, K15M, K100M

and DC-agent was Ludipress® LCE. Eight formulations were prepared as monolayered matrix tablets while four

formulations were prepared as three-layered matrix tablets by direct compression method. Drug release studies

were carried out according to the method given for Delayed Release Articles in USP XXVII. HPMC types and

ratios were found to be effective on drug release. Increasing amount and viscosity grade of HPMC resulted in a

decrease in release of drug from the matrices. Tablets containing low viscosity grade HPMC at inner and outer

layers presented release profiles close to or within the limits of pharmacopeia. Release data of three-layered

matrix tablet (F12) and the reference product (Isoptin® -KKH) which were in agreement with USP XXVII criteria,

were evaluated by mathematical models (zero order, first order, Higuchi, Hixson-Crowell, Korsmeyer-Peppas),

difference factor (f1) and similarity factor.

Md. Selim Reza et al., (2003)28 undertaken to investigate the effect of plastic, hydrophilic and hydrophobic

types of polymers and their content level on the release profile of drug from matrix systems. As the physico-

chemical nature of the active ingredients influence the drug retarding ability of these polymers, three different

drugs were used to evaluate their comparative release characteristics in similar matrices. Matrix tablets of

theophylline, diclofenac sodium and diltiazem HCl using Kollidon SR, Carnauba wax and Hydroxypropyl

methylcellulose (HPMC-15cps) were prepared separately by direct compression process Release profile

showed a tendency to follow zero-order kinetics from HPMC matrix systems whereas Fickian (Case I)

transport was predominant mechanism of drug release from Kollidon SR matrix system. The mean dissolution

time (MDT) was calculated for all the formulations and the highest MDT value was obtained with Carnauba wax

for all the drugs under investigate. The results generated in this study showed that the profile and kinetics of

drug release were functions of polymer type, polymer level and physico-chemical nature of drug. A controlled

plasma level profile of drug can be obtained by judicious combination of polymers and modulation of polymer

content in the matrix system.

Heinz R et al., (2000)29using Ludipress greatly simplifies formulation development and the manufacturing

process because only the active ingredient Ludipress and a lubricant need to be mixed briefly before being

compressed into tablets. The studies described here were designed to investigate the scale-up of Ludipress-

based formulations from laboratory to production scale, and to predict changes in tablet properties due to

changes in format, compaction pressure, and the use of different tablet presses. It was found that the tensile

strength of tablets made of Ludipress increased linearly with compaction pressures up to 300 MPa. It was also

independent of the geometry of the tablets (diameter, thickness, shape). It is therefore possible to give an

equation with which the compaction pressure required to achieve a given hardness can be calculated for a

given tablet form. The equation has to be modified slightly to convert from a single-punch press to a rotary

tableting machine. Tablets produced in the rotary machine at the same pressure have a slightly higher tensile

strength. The production of tablets based on Ludipress can be scaled up from one rotary press to another

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without problem if the powder mixtures are prepared with the same mixing energy. The tensile strength curve

determined for tablets made with Ludipress alone can also be applied to tablets with a small quantity (< 10%) of

an active ingredient.

REFERENCE

1. Gudsoorkar V. R., Rambhau D., “Sustained release of drugs”, The eastern pharmacist, 1993 Sept.: 17-21pp.

2. United States Pharmacopoeia XXIV – NF XIX, Asian edition, USP Convention Inc.2000: 2059pp.

3. Li. V.H., "Influence of drug properties and routes of drug administration on the design of sustained and

controlled release systems" Chapter 1 in "Controlled drug delivery : fundamentals and applications" edited by

Robinson J.R.,Vincent Lee, 2nd edition, Marcel Dekker Inc., Volume 29, 1978: 5-36pp.

4. Longer M.A., Robinson J.R. "Sustained release drug delivery system" chapter 91 in "Remington's

pharmaceutical sciences" 18th edition, Mack Publishing Company, 1990: 1675-1684pp.

5. Lordi N.G. "Sustained release dosage form" chapter 14 in "Theory and practice of Industrial Pharmacy"

edited by Lachman et al., 3rd edition, Varghese Publishing House, 1991: 430-431pp.

6. Welling P.G., Dobrinska M.R. "Dosing considerations and bioavailability assessment of controlled drug

delivery systems" chapter 6 in "Controlled drug delivery : fundamentals and applications" edited by Robinson

J.R., Vincent Lee, 2nd edition, Marcel Dekker Inc., Volume 29, 1978: 254-289pp.

7. Kumar S., Sharma, "Controlled Release Dosage Forms" The Eastern Pharmacist,2001: Sept.: 17-21pp.

8. Hui ho-wah, "Design and fabrication of oral controlled release drug delivery systems" chapter 9 in "Controlled

drug delivery; fundamentals and applications", edited by Robinson J.R., Vincent Lee, 2nd edition, Marcel

Dekker Inc., Volume 29, 1978: 391-420pp.

9. George M., Grass IV, Robinson J. "Sustained and controlled release drug delivery systems" chapter 6 in

"Modern Pharmaceutics" edited by Banker G.S., Rhodes C.T., 2nd edition, Marcel Dekker, 1990: 639-658pp.

10. Gudsoorkar V.R., Rambhau D., "Sustained release of drugs". The Eastern Pharmacist,1993: Nov.: 27-

35pp.

11. Motycka S., Naiva J.G., 'Influence of wax coatings on release rate of anions from ion exchange resin

beads", Journal of Pharmaceutical Sciences, 1993: 500-503.

12. Bechgaar H., Baggeson S., "Propoxyphene and norpro-poxyphene : Influence of type of controlled release

formulation on intra and intersubject variations", Journal of Pharmaceutical Sciences, 69 (11)1993 : 1327-1330.

13. Popli H., Sharma S.H., "Evaluation of sustained release formulations". The Eastern Pharmacist, Jan1990,

75-79.

14. Kumar V., Damien B., Potdar A.R., , "Designing of stability programme", The Eastern Pharmacist,

Aug.1992, 29-23.

15. . Kaushal A. et al. , "Regulatory requirements for oral controlled release drug delivery systems", Pharma

Times, Volume 33,2001, April, 14-17.

16. Skelly J.P., Barr W.H., "Regulatory assessment" chapter 7 in "Controlled drug delivery; fundamentals and

applications" edited by Robinson J.R., Vincent Lee, 2nd edition, Marcel Dekker Inc., Volume 29, 1978, 293-334.

17. Lee BJ, Ryu SG. Formulation and release characterstic of hydroxyl propyl cellulose matrix tablet containing

metformin. Drug ind. Pharma. 1999 apr,25(4):493-501pp

18. Ochoa L, Igartua M. Preparation of sustained release hydrophilic matrices by melt granulation in a high-

shear mixer. AAPS PharmSciTech. 2008;9(3):1016-24.

19. .Dong W, Bodmeier R. Encapsulation of lipophilic drugs within enteric microparticles by a novel

coacervation method. J Pharm Pharmacol. 2005 May;57(5):565-71

20. . Di Colo G, Zambito Y, Baggiani A. A site-specific controlled-release system for metformin.

Arzneimittelforschu. 2007

21. . Bailey CJ. Fixed-dose single tablet antidiabetic combinations. Vasc Health Risk Manag. 2008;4(3):481-92.

22. Lee BJ, Ryu SG, Cui JH. Controlled release of dual drug-loaded hydroxypropyl methylcellulose matrix tablet

using drug-containing polymeric coatings. J Pharm Pharmacol. 2008 Oct;60(10):1297-303

23. Talukder RM, Fassihi R. Development and in-vitro evaluation of a colon-specific controlled release drug

delivery system. Drug Dev Ind Pharm. 2008 Oct 31:1-15.

24. Cantor SL, Hoag SW. Formulation and Characterization of a Compacted Multiparticulate System for

Modified Release of Water-Soluble Drugs-Part II Theophylline and Cimetidine. Eur J Pharm Biopharm. 2004

Jul;58(1):51-9.

25. Vueba ML, Batista de Carvalho LA. Influence of cellulose ether polymers on ketoprofen release from

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Previous Page Next Page

anil 19-Jun-2011 15:24:52 IST

poornima.k 05-Dec-2011 12:03:32 IST

hydrophilic matrix tablets. Expert Opin Drug Deliv. 2006 Jul;3(4):541-8.

26. Corti G, Cirri M, Maestrelli F, Mennini N, Mura P. Sustained-release matrix tablets of metformin

hydrochloride in combination with triacetyl-beta-cyclodextrin. Zhonghua Yi Xue Za Zh. 2007 May

15;87(18):1238-40.

27. Kapat. Effects of polymer type, polymer:direct tabletting agent ratio and tabletting method on verapamil,

Ankara Ecz. Fak. Derg J. Fac. Pharm. Ankara.2004; 33(3) :125-137.

28. Md. Selim Reza, Mohiuddin Abdul Quadir, Syed Shabbir Haider, university of Dhaka. 2003.

29. Heinz R, Wolf H, Schuchmann H, End L, Kolter K. Formulation of tablet based on Ludipress and scale up

from Lab. Scale. Drug Dev Ind. Pharm.2000;26(5):513-521.

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