Date post: | 06-Jul-2018 |
Category: |
Documents |
Upload: | chandrashekhar-singh |
View: | 247 times |
Download: | 1 times |
of 27
8/18/2019 Gels - Pharmaceutics
1/27
Gels
8/18/2019 Gels - Pharmaceutics
2/27
• Characteristics of Gels
A) Swelling
When a gelling agent is kept in contactwith
a liquid that solvates it, then an
appreciable amount of liquid is takenup by the agent
and the volume increases !his process
isreferred to as swelling
8/18/2019 Gels - Pharmaceutics
3/27
") Syneresis
#any gels often contract spontaneously
on standing and e$ude some %uidmedium !his e&ect is known assyneresis !he degree to whichsyneresis occurs, increases as theconcentration of gelling agentdecreases !he occurrence of syneresisindicates that the original gel was
thermodynamically unstable
8/18/2019 Gels - Pharmaceutics
4/27
C) Ageing
Colloidal systems usually e$hibit slow
spontaneous aggregation !his processis referred to as ageing 'n gels, ageingresults in gradual formation of adenser network of the gelling agent
8/18/2019 Gels - Pharmaceutics
5/27
() Structure
!he rigidity of a gel arises from thepresence of a network formed by theinterlinking of particles of the gellingagents !he nature of the particle andthe type of force that is responsible for
thelinkages determine the structure of the
network and the properties of the gel
8/18/2019 Gels - Pharmaceutics
6/27
) *heology
Solutions of the gelling agents and
dispersion of %occulated solid arepseudo
plastic ie e$hibiting +on+ewtonian
%owbehaviour, characteri-ed by adecrease in
viscosity with increase in shear rate
8/18/2019 Gels - Pharmaceutics
7/27
• Gel forming substances
.olymers are used to give the structural networkwhich is essential for the preparation of gels Gelforming polymers are classi/ed as follows0
1 Natural polymer
a .roteins
i Gelatin ii Collagen
b .olysaccharides
i Alginic acid ii Agar iii !ragacanth iv
Sodium or .otassium carrageenan v .ectinvi Gellum Gum vii 2anthin viii Cassia tora
i$ Guar Gum
8/18/2019 Gels - Pharmaceutics
8/27
3 Semisynthetic polymers
a Cellulose derivatives
i 4ydro$yethyl cellulose ii #ethylcellulose
iii 4ydro$ypropyl methyl cellulose iv4ydro$ypropyl cellulose v Carbo$ymethyl
cellulose
3. Synthetic polymersa Carbomer
i Carbopol 561 ii Carbopol 567 iii
Carbopol 586
b .olo$amer
c .olyvinyl alcohol
d .olyacrylamide
e .olyethylene and its copolymers
8/18/2019 Gels - Pharmaceutics
9/27
4. Inorganic substances
a "entonite
b Aluminium hydro$ide5. Surfactants
a "ri95:
b Cetostearyl alcohol
8/18/2019 Gels - Pharmaceutics
10/27
.reparation of gels
• ;usion method
'n this method various wa$y materialare employed as gelling agents in nonpolar media (rug was added whenwa$es melted due to fusion Stirred tilluniform gel is formed
8/18/2019 Gels - Pharmaceutics
11/27
• (ispersion method
Gelling agent was dispersed in waterwith constant stirring at 1377 rpm for87mins (rug was dissolved in non aqsolution and added to above gel withconstant stirring
8/18/2019 Gels - Pharmaceutics
12/27
valuation of Gels
• Measurement of pH
!he p4 of various gel formulations wasdetermined by using digital p4 meter
8/18/2019 Gels - Pharmaceutics
13/27
• Drug Content
1 g of the prepared gel was mi$ed with177ml of suitable solvent Aliquots of
di&erent concentration were prepared bysuitable dilutions after /ltering the stocksolution and absorbance was measured
(rug content was calculated using theequation, which was obtained by linearregression analysis of calibration curve
8/18/2019 Gels - Pharmaceutics
14/27
• Viscosity Stuy
!he measurement of viscosity of theprepared gel was done with a"rook/eld =iscometer !he gels wererotated at 78, 7: and 1> rotationsper minute At each speed, the
corresponding dial reading was noted
8/18/2019 Gels - Pharmaceutics
15/27
• Spreabability
•
8/18/2019 Gels - Pharmaceutics
16/27
8/18/2019 Gels - Pharmaceutics
17/27
• 't is calculated by using the
formula0
S # @ B ! where,# wt tied to upper slide
@ length of glass slides
! time taken to separate the slides
8/18/2019 Gels - Pharmaceutics
18/27
• !"truability Stuy
!he formulations were /lled in thecollapsible tubes after the gels wereset in the container !he e$trudabilityof the formulation was determined interms of weight in grams required to
e$trude a 7> cm ribbon of gel in 17second
ki i i i d
8/18/2019 Gels - Pharmaceutics
19/27
• Skin irritation study
Guinea pigs 677>77 g) of either se$ wereused for testing of skin irritation !he
animals were maintained on standardanimal feed and had free access to water
!he animals were kept under standardconditions 4air was shaved from back ofguinea pigs and area of 6 sq cm wasmarked on both the sides, one side servedas control while the other side was test Gel
was applied >77 mg B guinea pig) twice aday for D days and the site was observedfor
any sensitivity and the reaction if any
8/18/2019 Gels - Pharmaceutics
20/27
#rae $eaction
7 +o reaction
1 slight patchy erythema,
3 slight but con%uent or
moderate but patchy erythema8 severe erythema with or without
edema
8/18/2019 Gels - Pharmaceutics
21/27
• 'n vitro (i&usion studies
!he di&usion studies of the prepared gels canbe carrying out in ;ran- di&usion cell for
studying the dissolution release of gels througha cellophane membrane Gel sample 7>g) wastaken in cellophane membrane and the di&usionstudies were carried out at 8D E 1F using 3>7 ml
of phosphate bu&er p4 D6) as the dissolutionmedium
;ive milliliters of each sample was withdrawnperiodically at 1, 3, 8, 6, >, :, D and h and
each sample was replaced with equal volume offresh dissolution medium !hen the sampleswere analy-ed for the drug content by usingphosphate bu&er as blank
8/18/2019 Gels - Pharmaceutics
22/27
8/18/2019 Gels - Pharmaceutics
23/27
8/18/2019 Gels - Pharmaceutics
24/27
• 4omogeneity
After the gels have been set in the
container, all developed gels weretested
for homogeneity by visual inspection !hey
were tested for their appearance andpresence of any aggregates
8/18/2019 Gels - Pharmaceutics
25/27
• Grittiness
All the formulations were evaluated
microscopically for the presence of any
appreciable particulate matter which was
seen under light microscope 4ence
obviously the gel preparation ful/ls the
requirement of freedom from particularmatter and from grittiness as desired forany topical preparation
8/18/2019 Gels - Pharmaceutics
26/27
.astes
• !hick sti& ointment that do notordinarily
%ow t body temperature and thereforeserve as protective covering over thearea where they are applied
• H37I of solid
• (ilatant %ow
8/18/2019 Gels - Pharmaceutics
27/27
Jellies
• Jellies are water soluble basesprepared from natural gums such astragacanth, pectin etc