INTRODUCTION OF GENERAL PHARMACOLOGY

PHARMACOLOGY:Pharmacology is the science

of drugs, including their ingredients, preparation, uses, and actions on the

body.

CLINICAL PHARMACOLOGY

It evaluate the pharmacological action of drug preferred route of administration and safe dosage range in human by clinical trails.

DRUGS:

Drugs are chemicals that alter functions of living organisms. Drugs are generally

given for the diagnosis, prevention, control or cure of disease.

PHARMACY

It is the science of identification, selection, preservation, standardisation,

compounding and dispensing of medical substances.

PHARMACODYNAMICS: The study of the biological and

therapeutic effects of drugs (i.e,“what the drug does to the body”).

PHARMACOKINETICS: Study of the absorption,

distribution metabolism and excretion

(ADME) of drugs (“i.e what the body does to the drug”).

PHARMACOTHERAPEUTICS: It deals with the proper selection

and use of drugs for the prevention and treatment of

disease.

TOXICOLOGY: It’s the science of poisons. Many

drugs in larger doses may act as poisons.

POISONS Poisons are substances that cause

harmful, dangerous or fatal symptoms in living substances

CHEMOTHERAPY: It’s the effect of drugs upon

microorganisms, parasites and neoplastic

cells living and multiplying in living organisms.

PHARMACOPOEIA: An official code containing a

selected list of the established drugs and

medical preparations with descriptions of their physical properties and tests for their

identity, purity and potency e.g. Indian Pharmacopoeia (I.P), British Pharmacopoeia

1. Plants – Atropine, Morphine2. Animals – Insulin3. Minerals – Calcium chloride and

Sodium bicarbonate4. Synthetics – Naloxone,

Lidocaine

SOURCES OF DRUGS

RECEPTOR

A structure on the surface of a cell (or inside a cell) that selectively receives and binds a specific substance. There are many receptors. There is a receptor for (insulin; there is a receptor for low-density lipoproteins (LDL); etc

MECHANISM OF DRUG ACTION

In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an enzyme or receptor.

DRUG NOMENCLATURE

Drugs are identified by one of three names:

Chemical name: -long name, describes the chemical constituents of the drug.

e.g :B-(3, 4 dihydroxyphenyl) -a-methylaminoethanol

› GENERIC NAME: -› Original chemical name of drug

assigned by the manufacturer that first develops it.

e.g epinephrine

TRADE NAME: - Brand name given by the company

that sells the drug e.g EpiPen® One drug may have more than one

trade name

•EFFICACY

Efficacy is the capacity to produce an effect. It has different specific meanings in different fields. In medicine, it is the ability of an intervention or drug to produce a desired effect

In medicine, efficacy indicates the capacity for beneficial change (or therapeutic effect) of a given intervention (e.g. a drug, medical device, surgical procedure, or a public health intervention).

POTENCY

Potency is the amount of a drug needed for it to have the maximum effect.

 A highly potent drug (e.g., morphine, alprazolam, chlorpromazine) evokes a larger response at low concentrations, while a drug of lower potency (ibuprofen, acetylsalicylic acid) evokes a small response at low concentrations. It is proportional to affinity and efficacy.

AFFINITY

Affinity is the ability of the drug to bind to a receptor.

Therapeutic effect A therapeutic effect is a consequence of a 

medical treatment of any kind, the results of which are judged to be desirable and beneficial. This is true whether the result was expected, unexpected .

As a simple example, the therapeutic effect of diphenhydramine, when used for nasal congestion, is to lessen mucous membrane secretions and the side effect is drowsiness. However, when used for insomnia, as in many over-the-counter preparations, the therapeutic effect of diphenhydramine is drowsiness and the side effect is mucous membrane dryness, which is undesirable, especially if the person using the agent for sleep is already suffering from dry membranes

. The more important issue is not the agent, but the situation in which the therapeutic agent is used; a change in the situation can easily totally reverse what is usually considered a therapeutic versus an undesirable side effect.

Adverse effect In medicine, an adverse effect is an undesired

harmful effect resulting from a medication or other intervention such as surgery.

Surgery may have a number of undesirable or harmful effects, such as infection, hemorrhage, inflammation, scarring, loss of function, or changes in local blood flow. They can be reversible or irreversible, and a compromise must be found by the physician and the patient between the beneficial or life-saving consequences of surgery versus its adverse effects. For example, a limb may be lost to amputation in case of untreatable gangrene, but the patient's life is saved. Presently, one of the greatest advantages of minimally invasive surgery, such as laparoscopic surgery, is the reduction of adverse effects.

Other nonsurgical physical procedures, such as high-intensity radiation therapy, may cause burns and alterations in the skin. In general, these therapies try to avoid damage to healthy tissues while maximizing the therapeutic effect.

Vaccination may have adverse effects due to the nature of its biological preparation, sometimes using attenuated pathogens and toxins. Common adverse effects may be fever, malaise and local reactions in the vaccination site. Very rarely, there is a serious adverse effect, such as eczema vaccinatum, a severe, sometimes fatal complication which may result in persons who have eczema or atopic dermatitis.

Diagnostic procedures may also have adverse effects, depending much on whether they are invasive, minimally invasive or noninvasive. For example, allergic reactions to radiocontrast materials often occur, and a colonoscopy may cause the perforation of the intestinal wall.

Allergic responses of drugs : A true drug allergy is caused by a series of chemical steps in the body that produce the allergic reaction to a medication.

The first time you take the medicine, you may have no problems. However, your body's immune system may produce a substance (antibody) called IgE against that drug. The next time you take the drug, the IgE tells your white blood cells to make a chemical called histamine, which causes your allergy symptoms. A drug allergy may also occur without your body producing IgE. Instead, it might produce other types of antibodies, or have other reactions that do not produce antibodies.

Most drug allergies cause minor skin rashes and hives.

Drug dependence addiction

Drug dependence means that a person needs a drug to function normally. Abruptly stopping the drug leads to withdrawal symptoms. Drug addiction is the compulsive use of a substance, despite its negative or dangerous effects.

A person may have a physical dependence on a substance without having an addiction. For example, certain blood pressure medications do not cause addiction but they can cause physical dependence. Other drugs, such as cocaine, cause addiction without leading to physical dependence.

DRUG TOLLERANCE AND ABUSE

• Drug tolerance  Decrease in susceptibility to the effects of a drug due to its continued administration.• Substance abuse, also known as drug abuse, is a patterned use of a substance (drug) in which the user consumes the substance in amounts or with methods which are harmful to themselves or others.

DRUG INTERACTION

A drug interaction is a situation in which a substance (usually another drug) affects the activity of a drug when both are administered together. This action can be synergistic (when the drug’s effect is increased) or antagonistic (when the drug’s effect is decreased) or a new effect can be produced that neither produces on its own. Typically, interactions between drugs come to mind (drug-drug interaction). However, interactions may also exist between drugs and foods (drug-food interactions), as well as drugs and medicinal plants or herbs (drug-plant interactions)

TERMINOLOGY Route of Administration – How the drug is actually given to the

patient?

Dose – How much of the drug should be

given to a patient Adult and pediatrics patients may

have two different doses of the same drug.

THERAPEUTIC DOSE – It is the amount of a substance to

produce the required effect in most patients.

TOXIC DOSE – It is the amount of a substance to

produce effects hazardous for an organism.

THERAPEUTIC RANGE-

Drug concentration in plasma should be between the minimum effective concentration in the plasma and the minimum toxic concentration

ONSET OF ACTION

The time it takes to reach the minimum effective concentration (MEC) after a drug is administered.• Peak action – The point at which a drug reaches its

highest blood or plasma concentration.

• Duration of action – The length of time the drug has a

pharmacologic effect.

PHARMACOLOGICAL ACTIONS

These are the effects of the drug on the body

Indications - Situations in which the drug

should be administered.

• Contraindications – Situations in which the drug should

not be administered.

SIDE EFFECTS

Actions of drugs on the body that occur in addition to the therapeutic effects and may be undesirable.

Teratogenic action – It is the effect of drug on the fetus causing

fetal malformation.

Hepatotoxicity – It is toxic action of a drug on the liver. Nephrotoxicity – It is toxic action of a drug on kidney.

ROUTES OF DRUG ADMINISTRATION

A- Enteral

B- Parenteral

The possible routes of drug entry into the body may be divided into two classes:

ENTERAL

- Drug placed directly in the gastrointestinal tract (G.I.T):1. Sublingual - placed under the

tongue2. Oral - swallowed 3. Rectum - Absorption through

the rectum

1- SUBLINGUAL/BUCCAL

Some drugs are taken as smaller tablets which are held in the mouth or under the tongue.

• Advantages: 1. Rapid absorption2. Drug stability3. Avoid first-pass effect

• Disadvantages:1. inconvenient2. small doses3. unpleasant taste of some drugs

2- ORAL

Advantages1. Convenient - can be self-

administered, pain free, easy to take

2. Absorption - takes place along the whole length of the GI tract

3. Cheap - compared to most other parenteral routes

This route allows the drug to be absorbed across the membranes of the stomach and/or the intestinal tract.

FIRST-PASS EFFECT

Hepatic metabolism of a drug when it is administered orally via the portal circulation before it reached systemic circulation.

The greater the first-pass effect, the less the agent will reach the systemic circulation

Advantages1. Used in unconscious patients and children 2. If patient is nauseous or vomiting 3. Good for drugs affecting the bowel such

as laxatives

Disadvantages1. Irritating drugs contraindicated2. Absorption may be variable

3- RECTAL

B- PARENTERAL ROUTES

1. Intravascular (I.V)- placing a drug directly into the blood stream

2. Intramuscular (I.M) - drug injected into skeletal muscle

3. Subcutaneous (S.C)- Absorption of drugs from the subcutaneous tissues

1- INTRAVASCULARAdvantages1. First pass metabolism is bypassed (100% bioavailability)2.Precise, accurate and almost immediate onset of

action 3. Large quantities can be given, pain free

Disadvantages1. Greater risk of adverse effects a. high concentration attained rapidly b. risk of embolism

3-SUBCUTANEOUS

Advantages:1. Slow and constant absorption 2. Absorption is limited by blood flow,

affected if circulatory problems exist 3. Concurrent administration of

vasoconstrictor will slow absorption

Advantages1.Gaseous and volatile agents and aerosols 2.Rapid onset of action due to rapid access to circulation a. Large surface area b. Thin membranes separates alveoli from circulation c. High blood flow

Disadvantages 1. Needs special apparatus2. Drugs may be irritants to the mucus membrane 3. For local effect in the bronchi, the bronchial tree

should not be obstructed with mucous plugs as in case of asthma

 

INHALATION

TOPICAL1. Mucosal membranes (eye drops, antiseptic) 2. Skin a. Dermal - rubbing in of oil or ointment

(local action) b. Transdermal - absorption of drug through

skin (systemic action)Advantages: i. Stable blood levels ii. No first pass metabolismDisadvantages: iii. drug must be potent or patch

becomes to large

Is determined by :1. The physical characteristics of the drug,

2. The speed which the drug is absorbed and/ or released,

3. The need to bypass hepatic metabolism and achieve high conc. at particular sites:

4. No single route of drug administration is ideal for all drugs in all circumstances

ROUTE OF ADMINISTRATION

FACTOR THAT INFLUENCE DRUG EFFECT

Weight Surface area Age Sex Gentic factors Physical Condition of the Patient  Psychological Condition of the

Patient Tolerance Time of Administration. Drug adminstration

GENE THERAPY

Gene therapy is the insertion of genes into an individual's cells and tissues to treat a disease, such as a hereditary disease in which a deleterious mutant allele is replaced with a functional one. Although the technology is still in its infancy, it has been used with some success. Scientific breakthroughs continue to move gene therapy toward mainstream medicine.

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