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34 terms

Semi Solid Dosage Forms

Semi Solid DFs, Routes of Administration, ointment, paste, cream, ideal properties of a base, characteristics of ointment bases & specific examples, general preparation methods of ointments
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Semisolid dosage form
-has properties that are those between solid and liquid, used for external application of skin or mucous membranes
-systems in pharmacy include:
--ointments, solidified emulsions, creams
--gels, magmas, rigid foam
--pastes, plasters
-vast majority intended for topical applications - common sites are skin, eye, nose, vagina, and rectum
-mainly intended for local effect
-however, systemic absorption s/b taken into account when using topical products in pregnant/nursing mothers
topical
-dermatologic product designed to deliver a drug to the skin in treating dermal disorders, skin is the target organ
transdermal
-preparation designed to deliver drugs through the skin to the general circulation for systemic effect, skin is Not the target organ
ointments
semisolid preparations intended for external application to skin/mucous membrane
-medicated/non-medicated
-non-medicated provide protective & lubricating effects
-main formulation components are drug and ointment base
ointment base
the vehicle in which the drug is dispersed in ointments
-Four general groups
--oleaginous (hydrocarbon) bases
--absorption bases
--water-removal bases
--water-soluble bases
Oleaginous bases
(hydrocarbon) bases: protect skin against escape of moisture (emollient)
-remain on skin for longer period of time/effective as occlusive dressings
-difficult to wash (greasy/lipophilic)
-aqueous preparations may be incorporated
-Includes: Petrolatum (yellow petroleum/petroleum jelly), White petrolatum (white petroleum jelly), Yellow ointment, White ointment
Petrolatum
(yellow petroleum/petroleum jelly) - purified mixture of semisolid hydrocarbons obtained from petroleum. e.g. Vaseline
-oleaginous base
White Petrolatum
(white petroleum jelly) - decolorized petrolatum (aesthetic appeal)
-oleaginous base
Yellow ointment
mixture of petrolatum (950 g) & yellow wax (50 g)
-oleaginous base
White ointment
mixture of petrolatum & white wax
-oleaginous base
Absorption bases
can absorb appreciable quantities of water/aqueous solutions w/o marked changes in consistency
-Two types
--Emulsifiable bases
--Emulsion bases (w/o emulsions)
Emulsifiable bases
do not contain water but become w/o emulsions upon incorporation of water.
-ex. hydrophilic petrolatum (cholesterol, stearyl alcohol, white wax & white petrolatum)
-absorption base
Emulsion bases
w/o emulsions that permit incorporation of additional quantities of water.
-ex. lanolin (purified wax-like substance obtained from wool of sheep)
-absorption base
Water Removal bases
(aka Washable) bases: o/w emulsions, can easily be removed from skin - called water washable emulsions, can absorb serious discharges.
-ex. Hydrophilic ointment USP
Hydrophilic ointment
-example of water removable (washable) base
-contains following ingredients: methylparaben, propylparaben, sodium lauryl sulfate, propylene glycol, stearyl glycol, white petrolatum, purified water
Water Soluble Bases
(aka Greaseless) bases: no oleaginous bases, completely water washable, mostly used for incorporation of solid substances,
-polyethylene glycol (PEG) ointment is an example of water soluble base that contains PEG 3350 and PEG 400
<600 clear, colorless liquids
>1000 are wax-like white material
>600 and <1000 are semi-solids
PEG ointment NF formula: PEG 3350, 400 g & PEG 400, 600 g
ointment preparation
based on nature of ingredients, prepared by two methods - incorporation and fusion
Incorporation
-drug powder or water soluble drug is incorporated into small quantities of ointment base
-components mixed until uniform preparation attained
-extemporaneous preparation (mortar & pestle/spatula used to rub ingredients together on ointment slab/pill tile/parchment paper)
-large scale manufacturing (stainless steel tank w/ counter sweep agitation & built-in homogenizer, ointment roller mill)
incorporation of drug powder
-drug powder can be incorporated by using spatula/mortar & pestle
-drug material is levigated (process of grinding an insoluble substance to fine powder, while wet) with small amt of vehicle or miscible component of formulation to form a concentrate
-Mineral oil & PEG may be used as levigating agents (wetting agents)
-concentrate is mixed with remainder of the base
incorporation of liquids
-small quantity of aqueous solution may be incorporated in oleaginous bases
-if aqueous solution is to be added to oleaginous base, solution may first be mixed with small amt of hydrophilic base & then w/ oleaginous bsase
-up to certain limit, water soluble substances can be mixed w/ water soluble bases
Fusion
all or some of components are melted together & cooled w/ constant stirring
-components not being melted are added to congealing mixture as it is being cooled & stirred
-process of fusion can be conducted in beaker/porcelain dish
-for large scale manufacturing, fusion carried out in large steam-jacketed kettles
-once congealed, ointment is passed through ointment mill
Creams
semisolid emulsion systems that have a creamy appearance as the result of reflection of light
-one or more medications may be dispersed in either w/o or o/w emulsion
-ex. vanishing cream (o/w emulsion containing large percentage of water, stearic acid & other oleaginous components)
-Application - primary is topical skin products, rectal & vaginal products
--can be applied in weeping or oozing surfaces
--patient & physician-preferred - easier to spread & remove
--many drugs available as both creams & ointments
Pastes
semisolid preparations that contain a Larger Amount of Solids compared to ointments
-stiffer than ointments, remain in place after application & can absorb serious secretions
-ex. zinc oxide paste, contains 25% ZnO in starch & white petrolatum, product is firm & can protect skin & absorb secretion better than zinc oxide ointments
Packaging
_ of Semisolid Dosage Forms:
-Topical dermatological products in jars/tubes
-ophthalmic, nasal, vaginal & rectal products always in tubes
-ointment jars made of opaque glass/plastic
-tubes made of aluminum/plastic
-ophthalmic, rectal, vaginal, aural & nasal semisolid preparations are packaged w/ special applicator tip
Gels
semisolid systems in which movement of dispersed medium is restricted by interlacing three dimensional network of particles/solvated macormolecules of dispersed phase
-also defined as system of at least two constituents, consisting of condensed mass enclosing an interpenetrated by liquids
-when coherent matrix is rich in liquid, product often called jelly (ex. table jelly)
-when liquid is removed & only framework remains, gel is known as xerogel
Types of Gels
-Two phase gel vs. Single phase gel
-Inorganic gels vs. Organic gels
Two phase gels
(or magma)
-gel consists of floccules of small & distinct particles rather than large molecules
-gels are thixotropic (semisolid on standing but becomes liquid on agitation)
-includes inorganic gels
Single phase gels
when gel consists of macromolecules existing as twisted/matted strands, gel structure is called one phase system because no definite boundary exists between dispersed macromolecule & liquid
-network of gelling structure are held together by stronger van der Waals forces
-ex. tragacanth & carboxymethylcellulose
-includes organic gels
Inorganic gels
two phase (gel) systems, ex. aluminum hydroxide gel, bentonite magma
Organic gels
single phase gels, condensed matrix is dissolved in liquid media to form homogeneous gelatinous mixture
-when gels contain water, they are called hydrogel. e.g. gelatin, tragacanth, jelly
-when gels contain organic liquid, they are called organogel. ex. petrolatum, mineral oil/polyethyelene gel (plastibase)
Properties of Gels
special properties that facilitate drug absorption & delivery (gels)
•syneresis
•swelling
•imbibition
Syneresis
When a gels stands for some time, it often shrinks because some of the liquid is squeezed out of the system
Swelling
The opposite of syneresis; when a gel takes up some liquid and increases in volume
Imbibition
When a gel takes up a certain amount of liquid with no measurable increase in volume