Pharmaceutics

1. Gels
 Are semisolid systems consisting of either
suspensions made up of small inorganic
particles or large organic molecules in aliquid
vehicle rendered jelly like by the addition of a
GELLING AGENT.
 Sometimes calledJELLIES

2.  High degreeof physical/chemical cross
linking may be involved
 interlacing/ internalfriction
 Resulting into highviscosity
 Responsible for semi-solidstate

3. Terminologies relatedto gel
 Imbibition:
 Takingup of acertain amount of liquid without a
measureable increase involume
 Swelling:
 Takingup of aliquid by gel with anincreasein volume
 Syneresis
 Formof instability in which separation of solvent phase
occurscozof elastic contraction of polymeric molecules
 Thixotropy
 Aphenomenonin which if gel is agitated it may become
fluid and remain in solid state only after remaining
undisturbed for aperiod of time i.e sol gel transfer

4.  Examplesof GellingAgents
 1. Carbomers 910; 934; 934P;940;
941;1342
 2. Carboxymethylcellulose; natural gums
 *0.5 to 2.0%concentration in water

5. Cl asses of G
el
 2phase systems - separation between the insoluble matter and
liquid vehicle is observed. This type contains inorganic materials
also small particles distribute them in liquid in the form of
floccules(inorganic)(magma)
 Example: Al(OH)3Gel
 Single phase gel - consist of organic macromolecules
uniformly distributed throughout the liquid where no
apparent boundary is seen(organic)
 Example: NaCMCandTragacanthGel(twisted mated strands wound
together by stronger vander waals forces to form crystalline and
amorphous regions)
 Continuous phase- commonly aqueous where alcohol and gels may
be
 useascontinuous phase(organogels)
 Example: Mineral oil +polyethylene resin =oleaginous ointment
base
 Hydrogels
 Include ing that are dispersible ascolloidals they include organic
hydrogels natural and synthetic gums e.g silicaand methyle
cellulose

6. Types of G
el
 Type1-Heterogels
 Irreversible system
 3-dim structure
 Held by covalentbonds
 Showsynerisis
 Type 2-Commonly usedgels
 Heat reversible
 Held byh-bonds
 Gelling is influenced by pH additives
 Showsynerisis

7.  Characteristics ofGels
 Gelsmay be thicken on standing, forming a
THIXOTROPE, and must be shakenbefore use
to liquefy the gel and enable pouring –
Aluminum HydroxideGel
 Becauseof high degree of attraction between
the dispersed phaseand water medium, the gels
remain fairly uniform upon standing and does
not readilysettle

8. Preparation of gels and
magmas:
Prpeared by freshly
precipitating the dispersed
phase in order to achieve a
fine degree of subdivision of
the particlesand gelatinous
character tothose particles
Desired gelatinous ppt
results when solutions of
inorganic agents react to
form an insolublechemical
having ahigh attractionfor
water.
Asthe microcrystalline
particles of ppt develop they
strongly attract water to
yield gelatinous particles
which for gelppt

9. Preparation of gels and
magmas
Other magma and gels may be
prepared by +ion in water of
inorganic chemical andhydrated
form constitutes the dispersed
phaseof dispersion
In addition to water vehicle
other agents such aspropylene
glycol, hydroxy propyl cellulose
etc maybeusedtto enhancegel
formation
Cozof high degreeof attraction
b/w disperse phaseand the aq
medium in both magmas and
gels these prep remain fairly
uniform on standing with little
settling ofdisperse phase
Onlongstandind synerisis may
be seenbut on little shaking
uniformityis re established
Label should have statement
shakewell beforeusefreezing
must beavoided

10.  Preparation ofGels
1. Byfreshly precipitating the dispersephaseupon
reacting an inorganic agents, agelatinous
precipitate results
 Example: Preparation of Al(OH)3 gel isby
reacting Al(Cl)3+Na2CO3
NaHCO3

11.  Preparation ofGels
2. By direct hydrating the inorganic material in
water
 Al2O3 + H2O Al(OH)3
 Examples: Aluminum Hydroxide Gel;Alugel;
Amphogel; Ce-lu-gel; Cremalin; Hydroxal;
Vanogel; Aluminum Phosphate Gel
(Phosphagel) -Antacid

12. Polyvinyl alcohols areusedfor gel preparation
in skin formulations when they are applied
these alcohol evaporate leaving athin layer
on skin

13. Examples of Gel
 Clobetasol propionate-TermovateGel
Dermatologic:Antipruritic

14. Example of Gel
 Acetic acid-Aci-jel
Vaginal: Restoration and maintenanceof
acidity

15. Example of Gel
 Progesterone- CrinoneGel
Vaginal: Bioadhesive gel;Progesterone
supplement andreplacement

16. Uses of gel
 Lubricant forcatheters
 Basesfor patchtesting
 NaCl gel forelectrocardiography
 FloucinonideGelfor anti- inflammatory
corticosteriod
 NaFluoride & Phosphoric acid gel –dental
careprophylactic
 TretionoinGelfor treatment of acne
 Prostaglandin Gel –intravaginal

17.  Gelsand Magmas
 Are considered colloidal dispersion since they
contain particles of colloidal dimensions
 APPROPRIATENAMES (COLLOIDALDISPERSION)
 SOLS–term to designate adispersion of solid in
either a liquid, solid or gasdispersion medium


 A. Prefix HYDRO–water asdispersion medium
so called HYDROSOL
B. Prefix ALCO–alcohol asthe dispersion
medium so calledALCOSOL
C.AEROSOL–dispersion of solid or liquidin
gaseous phase

18. Examples Of Topical Gels
 1. Erythromycin and benzoyl peroxide topical
gel - Benzamycin
 2. Clindamycin Topical gel - Cleocin T Topical
Gel
 3. Benzoyl Peroxide Gel - Desquam-X 10 Gel -
acne vulgaris
 4. Hydroquinone Gel - Solaquin Forte Gel -
bleach for hyperpigmented skin
 5. Salicylic Acid Gel - Compound W Gel -
keratolytic
 6. Desoximetasone Gel - Topicort - anti-
Inflammatory, antipruritic agent

19.  ExamplesofTopicalGel
 Active Ingredient Proprietary Gelling agent Route andUse
1. Acetic acid Aci-jel Tragacanth, acacia Vaginal: restorationand
maintenance of acidity
Carbomer 940Acne vulgaris
Carbomer 934PAcnevulgaris
Cleocin TGel
TermovateGel Carbomer 934 Antipruritic
Methylcellulose Nasal:hematologic
2. Becaplermin RegranexGel NaCMC Dermatologic
3. Benzoly peroxide Desquam-X Gel
4. Clindamycin
5. Clobetasol
6. Cyanocobalamin Nascobal
7. Desoximetasone Topicort Gel Carbomer940 Anti-inflammatory;
antipruritic
Metro-Gel
CrinoneGel
8. Metronidazole
9. Progesteron
supplement
Retin–A
Carbomer 934PVaginal-bacterial
Carbomer934P Progesterone
Hydroxypropyl Acne vulgaris
10. Tretinoin
cellulose

20.  TRANSDERMALPREPARATIONS
 Ointments,creams,gelsdesignedto delivera drug
systematically by addition of PENETRATION
ENHANCERS to the topicalvehicle
 Examples of PenetrationEnhancers

 Dimethyl sulfoxide (DMSO), ethanol, propylene
glycol, glycerin, polyethylene glycol, urea, dimethyl
acetamide, sodiumlauryl
sulfate, poloxamers, Spans, Tweens, lecithin, and
terpenes
Example: PLURONIC lecithin organogel (PLO)–
Pluronic (Poloxamer) F127gel (usually20% to 30%
concentration)