Magmas and Gels dosage form designs

1. MAGMAS AND GELS
Dr SAMIA GHANI
M.PHIL PHARMACEUTICS
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2. Definition
◦ Gels are defined as semisolid systems consisting of dispersions made up of
either small inorganic particles or large organic molecules enclosing and
interpenetrated by a liquid.
◦ Gels are also defined as semi-rigid systems in which the movement of the
dispersing medium is restricted by an interlacing three-dimensional network
of particles or solvated macromolecules of the dispersed phase. A high
degree of physical or chemical cross-linking may be involved. The increased
viscosity caused by the interlacing and consequential internal friction is
responsible for the semisolid state.
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3. Colloidal dispersions
◦ Some gel systems are as clear as water, and others are turbid because the
ingredients may not be completely molecularly dispersed (soluble or
insoluble), or they may form aggregates, which disperse light. The
concentration of the gelling agents is mostly less than 10%, usually in 0.5%
to 2.0% range, with some exceptions.
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There is no precise point at whichthe size of a particle in a dispersion can
be con-sidered to be colloidal, there is a generallyaccepted size range. A
substance is said to becolloidal when its particles fall between 1 nm
and0.5μm.
Colloidal particles are usually larger thanatoms, ions, or molecules and,
generally, consist of aggregates of many molecules, although incertain
proteins and organic polymers, singlelarge molecules may be of colloidal
dimensionand form colloidal dispersions.

4. Difference between true solution
and colloidal dispersion
◦ larger particle size of the disperse phase of the colloidal dispersion.
◦ Optical properties of two systems (True solutions do not scatter light and,
therefore, appear clear, but colloidal dispersions contain opaque particles that
do scatter light and thus appear turbid upon observing using tyndall effect.)
◦ Nature of the dispersing phase with respect to dispersion medium: The
attraction or lack of attraction between the disperse phase and the dispersion
medium affects both ease of preparation and the charater of the dispersion.
If the disperse phase interacts appreciably with the dispersion medium, itis said to
be lyophilic, meaning solvent loving. (easier to prepare, greater stability).
If the degree of attraction is small, the colloid is termed lyophobic, or solvent
hating.
A third type of colloidal sol, termed an association or amphiphilic colloid, is
formed by grouping or association of molecules that exhibit both lyophilic and
lyophobic properties.
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5. ◦ Gels in which the macromolecules are distributed so that no apparent
boundaries exist between them and the liquid are called single-phase gels.
When the gel mass consists of floccules of small, distinct particles, the gel is
classified as a two-phase system and frequently called a magma or a milk.
Gels and magmas are considered colloidal dispersions, because they contain
particles of colloidal dimension.
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6. ◦Gels and Magmas
◦ Are considered colloidal dispersion since they contain particles
of colloidal dimensions
◦ APPROPRIATE NAMES (COLLOIDAL DISPERSION)
◦ SOLS – term to designate a dispersion of solid in either a liquid, solid or gas
dispersion medium
◦ A. Prefix HYDRO – water as dispersion medium so called HYDROSOL
◦ B. Prefix ALCO – alcohol as the dispersion medium so
called ALCOSOL
◦ C. AEROSOL – dispersion of solid or liquid in
gaseous phase
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7. Terminology Related to Gels
◦ Imbibition: is the taking up of a certain amount of liquid without a
measurable increase in volume.
◦ Swelling: is the taking up of a liquid by a gel with an increase in volume.
Only liquids that solvate a gel can cause swelling. The swelling of protein
gels is influenced by pH and the presence of electrolytes.
◦ Syneresis: occurs when the interaction between particles of the
dispersed phase becomes so great that on standing, the dispersing
medium is squeezed out in droplets and the gel shrinks. Syneresis is a
form of instability in aqueous and nonaqueous gels.
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8. ◦ Thixotropy A phenomenon in which if gel is agitated it may become
fluid and remain in solid state only after remaining undisturbed for a
period of time i.e sol gel transfer
◦ It is a reversible gel–sol formation with no change in volume or
temperature, a type of non-Newtonian flow.
◦ A xerogel is formed when the liquid is removed from a gel and only the
framework remains. Examples include gelatin sheets, tragacanth ribbons,
and acacia tears.
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9. Classification and Types of Gels
◦ The classification scheme divides gels into hydrogels and organogels with
some additional subcategories.
◦ Hydrogels include ingredients that are dispersible as colloidals or soluble
in water; they include organic hydrogels, natural and synthetic gums, and
inorganic hydrogels. Examples include hydrophilic colloids such as silica,
bentonite, tragacanth, pectin, sodium alginate, methylcellulose, sodium
CMC, and alumina, which in high concentration form semisolid gels.
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10. ◦ Organogels include the hydrocarbons, animal and vegetable fats, soap
base greases, and the hydrophilic organogels. Included in the
hydrocarbon type is Jelene, or Plastibase, a combination of mineral oils
and heavy hydrocarbon waxes with a molecular weight of about 1300.
◦ Petrolatum is a semisolid gel consisting of a liquid component together
with a proto-substance and a crystalline waxy fraction. The crystalline
fraction provides rigidity to the structure, while the proto-substance, or
gel former, stabilizes the system and thickens the gel.
◦ The hydrophilic organogels, or polar organogels, include the polyethylene
glycols of high molecular weight, the carbo-waxes.
◦ They are soluble toabout 75% in water and are completely wash-able. The
gels look and feel like petrolatum. They are nonionic and stable.
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11. General classification and
description of gels
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12. ◦ Jellies are a class of gels in which the structural coherent matrix contains
a high proportion of liquid, usually water. They usually are formed by
adding a thickening agent such as tragacanth or carboxymethyl cellulose
to an aqueous solution of a drug substance. The resultant product is
usually clear and uniformly semisolid.
◦ Jellies are subject to bacterial contamination and growth, so most are
preserved with antimicrobials. Jellies should be stored with tight closure,
because water may evaporate, drying out the product.
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13. Preparation of Magmas and Gels
◦ Some magmas and gels (inorganic) are prepared by freshly precipitating the
disperse phase to achieve a fine degree of subdivision of the particles and a
gelatinous character to those particles. The desired gelatinous precipitate
results when solutions of inorganic agents react to form an insoluble
chemical having a high attraction for water. As the microcrystalline particles
of the precipitate develop, they strongly attract water to yield gelatinous
particles, which combine to form the desired gelatinous precipitate.
◦ Example: Preparation of Al(OH)3 gel is by reacting Al(Cl)3 + Na2CO3 +
NaHCO3
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14. Prep conti…
◦ Other magmas and gels may be prepared by directly hydrating the
inorganic chemical, which produces the disperse phase of the
dispersion. In addition to the water vehicle, other agents as propylene
glycol, propyl gallate, and hydroxypropyl cellulose may be used to
enhance gel formation.
◦ Al2O3 + H2O Al(OH)3
◦ Examples: Aluminum Hydroxide Gel; Alugel; Amphogel; Ce-lu-gel;
Cremalin; Hydroxal; Vanogel; Aluminum Phosphate Gel (Phosphagel) -
Antacid
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15. ◦ Because of the high degree of attraction between the disperse phase and
the aqueous medium in both magmas and gels, these preparations remain
fairly uniform on standing, with little settling of the disperse phase.
However, on long standing, a supernatant layer of the dispersion medium
develops, but the uniformity of the preparation is easily reestablished by
moderate shaking. To ensure uniform dosage, magmas and gels should be
shaken before use and a statement to that effect must be included on the
label of such preparations.
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16. Gel formation considerations
◦ As a hot colloidal dispersion of gelatin cools,the gelatin macromolecules lose
kinetic energy.With reduced kinetic energy, or thermal agitation, the gelatin
macromolecules are associated through dipole–dipole interaction into
elongated or thread like aggregates. The size of these association chains
increases to the extent that the dispersing medium is held in the interstices
among the interlacing network of gelatin macro-molecules, and the viscosity
increases to that of a semisolid. Gums, such as agar, Irish moss, algin, pectin,
and tragacanth form gels by the same mechanism as gelatin.
◦ Inorganic salts will compete with the water in a gel and cause gelation at lower
concentrations. This is usually reversible; upon addition of water, the gels will
reform. Because alcohol is not a solvent or precipitant, it may cause
precipitation or gelation, lowering the dielectric constant of the medium and
tending to dehydrate the hydrophilic solute. Alcohol lowers the concentrations
at which electrolytes salt out hydrophilic colloids. Phase separation by adding
alcohol may cause coacervation.
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17. Conti…
◦ Aqueous polymer solutions, especially of cellulose derivatives, are stored
for approximately 48 hours after dissolution to promote full hydration
and maximum viscosity and clarity. Any salts are added at this point
rather than dissolving in water prior to adding polymer; otherwise the
solutions may not reach their full viscosity and clarity.
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18. EXAMPLES OF GELLING AGENTS
◦ Gelling agents include acacia, alginic acid, bentonite, carbomer, CMC
sodium, cetostearyl alcohol, colloidal silicon dioxide, ethylcellulose,
gelatin, guar gum, hydroxy ethylcellulose, hydroxypropylcellulose,
hydroxypropyl methylcellulose, magne-sium aluminum silicate,
maltodextrin, methylcel-lulose, polyvinyl alcohol (PVA),
povidone,propylene carbonate, propylene glycol alginate, sodium
alginate, sodium starch glycolate, starch, tragacanth, and xanthan gum.
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19. Name Source Physical
properties
Conc. &
use
comments
Alginic acid seaweed Tasteless,
odorless,
yellowish-
white, fibrous
powder
1% to 2%
conc. As
thickening
agent
Swells about 200 to
300 times in water
Bentonite Colloidal
hydrated
aluminium
silicate
Grey to white
powder
5% conc. Swells about 12
times its volume in
water
Carbomer
(carbopol)
resins
high–mol-
weight
allylpentaeryth
ritol–cross-
linked acrylic
acid–based
polymers
modified with
C10 to C30
alkyl acrylates.
fluffy white dry
powders
0.5% and
1.0%
aqueous
dis-
persions
are pH 2.7
to 3.5 and
2.5 to 3.0,
respectivel
y
Carbomer 910 is
effective atvery low
concentrations
when low viscosity
isdesired and is
frequently used for
producingstable
suspensions.
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20. Name Source Physical
properties
Conc. & use comments
CMC synthetic Soluble in either
hot, cold water,
anioinic with very
low or non-
foaming surface
activity
4% to 6% Varied based
upon
formulation
kind,
(hydrogels
45.33 g/g)
Colloidal
silicone dioxide
Synthetic adsorbs large
quantities of water
without liquefying.
The viscosity is
temperature
independent. pH
change affect the
viscosity: most
effective pH 7.5.
Form gel when
combined with 1-
dodecanoland n-
dodecane.
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21. 21
Name Source Physical Conc. & use comments
Gelatin Animal
source
Tasteless, odorless,
pale yellow,
insoluble in
organic solvents,
oluble in polar
solvents
Gelatin
absorbs and
retain water
dispersed in
hot water and
cooledto form
gels
Magnesium
aluminum
silicate, or
Veegum
Naturally
occuring
mineral
Off-white to
creamy white,
odorless, tasteless,
slippery small
flakes or fine
micronized
powder.
10% conc.
forms a firm
thixo-tropic
gel.
Best used at
pH 3.5
It may bind to
some drugs
and limit their
bio-availability.
Methylcellulose Derivative of
cellulose
White, pale yellow,
odorless, tasteless,
hygroscopic
5% conc form
gel
hydrates slowly
in hot water

22. 22
◦ Plastibase, or Jelene, is a mixture of 5% low molecular weight polyethylene
and 95% mineraloil.
◦ Poloxamer, or Pluronic, gels are made from selected forms of
polyoxyethylene–polyoxypro-pylene copolymers in concentrations ranging
from 15% to 50%. Poloxamers generally are waxy white free-flowing granules
that are practically odorless and tasteless.
◦ PVA is used at concentrations of about 2.5%in the preparation of various jellies
that dry rapidly when applied to the skin. Borax is a good agent that will gel
PVA solutions. For best results, disperse PVA in cold water, followed by
hotwater. It is less soluble in the cold water.
◦ Povidone at the higher molecular weights can be used to prepare gels in
concentrations up to about 10%.
◦ Sodium alginate can be used to produce gels in concentrations up to 10%.
◦ Tragacanth gum has been used to prepare gels that are most stable at pH 4
to 8. These gels must be preserved with either 0.1% benzoic acid or sodium
benzoate or a combination of0.17% methyl paraben and 0.03% propylparaben.
These gels may be sterilized by autoclaving.

23. Examples of Gel
◦ Clobetasol propionate- Termovate Gel
Dermatologic: Antipruritic
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24. Example of Gel
◦ Acetic acid- Aci-jel
Vaginal: Restoration and maintenance of acidity
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25. Example of Gel
◦ Progesterone- Crinone Gel
Vaginal: Bioadhesive gel; Progesterone supplement and replacement
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26. Example
◦ One official magma, Bentonite Magma, NF, used as a suspending
agent, finds application in the extemporaneous compounding of
prescriptions
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27. Example
◦ Sodium Fluoride and Phosphoric Acid Gel, USP, is applied topically to
the teeth as a dental care prophylactic.
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28. Other examples
◦ Other official gels applied topically include Fluocinonide Gel, USP, an anti-
inflammatory corticosteroid, and Tretinoin Gel, USP, an irritant that stimulates
epidermal cell turnover, causes peeling, and is effective in the treatment of
acne.
◦ Examples of such drugs and drug products are erythromycin and benzoyl
peroxide topical gel (Benzamycin Topical Gel, Dermik Laboratories);
clindamycin topical gel (Cleocin T Topical Gel, Pharmacia & Upjohn);
clindamycin and benzoyl peroxide topical gel (BenzaClin, Dermik); and
benzoyl peroxide gel (Desquam-X 10 Gel, Westwood-Squibb) used in the
control and treatment of acne vulgaris;
◦ Hydroquinone gel (Solaquin Forte Gel, ICN), a bleach for hyperpigmented
skin; salicylic acid gel (Compound W gel, Whitehall), a keratolytic; and
desoximetasone gel (Topicort Gel, Medicis Dermatologics) and augmented
betamethasone dipropionate topical gel (Diprolene, Schering), anti-
inflammatory and antipruritic agents.
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29. Uses of gel
◦ Lubricant for catheters
◦ Bases for patch testing
◦ NaCl gel for electrocardiography
◦ Floucinonide Gel for anti- inflammatory corticosteriod
◦ Na Fluoride & Phosphoric acid gel – dental care prophylactic
◦ Tretionoin Gel for treatment of acne
◦ Prostaglandin Gel – intravaginal
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30. Bentonite Magma, NF
◦ Bentonite magma is a preparation of 5%bentonite, a native colloidal
hydrated aluminumsilicate, in purified water.
◦ Forms thixotropic gels and The thixotropy occurs only when the
bentonite concentration is somewhat above 4%.
◦ Bentonite magma is employed as a suspend-ing agent. Its alkaline pH
must be considered,because it is undesirable for certain drugs. Fur-
thermore, because the suspending capacity ofthe magma is drastically
reduced if the pH islowered to about pH 7, another suspendingagent
should be selected for drugs requiring aless alkaline medium rather than
making ben-tonite magma more acidic.
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31. Aluminum Hydroxide Gel, USP
◦ an aqueous suspension of a gelatinous precipitate composed of insoluble
aluminum hydroxide and the hydrated aluminum oxide, equivalent to
about4% aluminum oxide.
◦ To the gel, the USP permits the addition of peppermint oil, glycerin, sorbitol,
sucrose, saccharin, or other flavorants and sweeteners as well as suitable
antimicrobial agents.
◦ This antacid preparation is a white, viscous suspension.
◦ It is effective in neutralizing a portion of the gastric hydrochloric acid and by
virtue of its gelatinous, viscous, and insoluble character, coats the inflamed
and perhaps ulcerated gastric surface, and is useful in the treatment of
hyperacidity and peptic ulcers.
◦ The main disadvantage to its use is its constipating effects.
◦ The usual dose is 10mL four or more times a day,that is, after meals and at
bedtime.
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32. Milk of Magnesia
◦ Milk of magnesia is a preparation containing
7%to8.5%magnesiumhydroxide.Itmaybeprepared by a reaction between sodium
hydroxide and magnesium sulfate (1), diluted solutions being used to ensure a fine,
flocculent, gelatinous precipitate of magnesium hydroxide.
◦ 2NaOH+MgSO4→Mg(OH)2+Na2SO4
◦ MgO+H2O→Mg(OH)2
◦ Milk of magnesia possesses reasonable acid-neutralizing ability, and a dose of 5mL will
neutralize about 10 mEq of stomach acid. However, to neutralize more acid a higher
dose, such as 15 mL, is usually necessary,
◦ When a laxative effect is desired, a bedtime dose of 30 to 60mL of milk of magnesia
will suffice very nicely by the next morning.
◦ Milk of magnesia is best stored in a tight container, preferably at 0°C to 35°C. Freezing
resultsin a coarsening of the disperse phase, and temperatures above 35°C decrease
the gel structure.
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33. Starch Glycerite
◦ Starch. 100g
◦ Benzoic acid 2g
◦ Purified water. 200g
◦ Glycerin. 700g
◦ The starch and benzoic acid are rubbed in the water to a smooth
mixture. The glycerin is added and mixed. The mixture is heated to
140°C with constant gentle agitation until a translucent mass forms. The
heat ruptures the starch grains and permits the water to reach and
hydrate the linear and branched starch molecules, which trap the
dispersion medium in the interstices to form a gel. Starch glycerite has
been used as a topical vehicle and protectant.
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34. Lubricating Jelly Formula
◦ Methylcellulose, 4000 cP. 0.8%
◦ Carbopol 934. 0.24%
◦ Propylene glycol. 16.7%
◦ Methylparaben 0.015%
◦ Sodium hydroxide, qs ad. pH 7
◦ Purified water, qs ad. 100%
◦ Lubricating jellies are used to assist in medical procedures, to aid in
insertion of various devices and drugs, including catheters and
suppositories, and as vehicles for some drug products, especially in
extemporaneous compounding.
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35. TRANSDERMAL PREPARATIONS
◦ Ointments, creams, gels designed to deliver a drug systematically by
addition of PENETRATION ENHANCERS to the topical vehicle
◦Examples of Penetration
Enhancers
◦ Dimethyl sulfoxide (DMSO), ethanol, propylene glycol, glycerin,
polyethylene glycol, urea, dimethyl acetamide, sodium lauryl sulfate,
poloxamers, Spans, Tweens, lecithin, and terpenes
◦ Example: PLURONIC lecithin organogel (PLO) – Pluronic
(Poloxamer) F127 gel (usually 20% to 30% concentration)
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36. PROPER ADMINISTRATION
AND USE OF DISPERSE SYSTEMS
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37. ◦ Oral solution can be measured by spoonful or administered dropwise,
depending on the appropriate dosage.
◦ Many reconstituted products in an oversized bottle that allows for the
proper shaking of the product prior to its use.
◦ Oral antibiotic suspensions intendedto treat a middle ear infection have
been mis-takenly administered directly into the ear bysome patients or
guardians. Thus, the pharma-cist should review with the patient the
properroute of administration.
◦ Because theseare reconstituted with purified water stabilityproblems
with the drug usually dictate that it bestored in the refrigerator until it is
consumed.
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38. ◦ Certain suspensions, such as aluminum hydroxide gel, cholestyramine,
and kaolin, by virtue of their active ingredients interfere with absorption
of other drugs. For example, cholestyramine has been shown to interfere
with and decrease the bioavailability of warfarin, digitoxin, and thyroid
hormones. The pharmacist should be aware of this and make
recommendations to help avoid this drug interaction whenever possible.
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