March 16 - Semisolid Dosage Forms

Question 1

What are semisolid dosage forms?

Answer 1

Intended for topical application and generally placed on the skin. Includes ointments, creams and gels. Some modified for ophthalmic, nasal, vaginal, or rectal use. Most contain an active component (API or drug) but some used for physical effects as protectants or lubricants. Topical products can be used for local or systemic effect. Inadvertent systemic effect always be considered

Question 2

What is the difference between transdermal products and topical dermatological products?

Answer 2

Topical dermatological products delivers drug locally into the skin and the skin is the target organ
Transdermal products deliver drugs systemically through the skin into the blood; target organ is not skin

Question 3

Describe ointments

Answer 3

Semisolid preparations for external application to skin or mucous membranes. May be medicated or non-medicated. Non-medicated are used for protective, emollient or lubricating activity

Question 4

What are the four classifications of ointments bases?

Answer 4

Oleaginous
Absorption
Water-removable
Water-soluble

Question 5

Describe oleaginous ointments

Answer 5

Hydrocarbon bases (like vaseline)
Emollient effect (protect against loss of moisture)
Occlusive (air and water-proof)
Remain on skin long time and difficult to wash off
Water and aqueous solution may be incorporated into this base but only with difficulty and in small quantitiy
Liquid petrolatum (mineral oil) used as levigating agent to incorporate solids

Question 6

Describe absorption bases

Answer 6

Water in oil emulsions
There are two types:
1. Allows incorporation of water to form w/o emulsion (eucerin, hydrophilic petrolatum, anhydrous lanolin Aquaphor)
2. Already a w/o emulsion (hydrous lanolin)
Provide a way to incorporate aqueous solutions into oleaginous bases
Used as emollients
Difficult to wash off

Question 7

Describe water-removable bases

Answer 7

Essentially are o/w emulsions
Easily removed by washing and since continuous phase is water can be diluted with water
Cosmetically acceptable and useful for weeping skin conditions
Hydrophilic ointment USP, dermabase, unibase are examples
Consider preservation

Question 8

Describe water-soluble bases

Answer 8

Referred to as ‘greaseless’ since they contain no oleaginous components
Completely water washable
Usually contain polyethylene glycol (PEG)
Ex. Polyethylene glycol ointment NF, PolyBase

Question 9

What are the considerations taken into account during the selection of a base?

Answer 9

Topical or percutaneous (transdermal)
Rate of drug release
Occlusion wanted
Drug stability
Drug solubility/skin feel
Easy/difficult removal
Site of application

Question 10

What are the attributes of oleaginous ointments?

Answer 10

Anhydrous, hydrophobic, difficult to spread, not washable, drug incorporation are solid/oils, poor drug release, occlusive. Ex. White petrolatum

Question 11

What are the attributes of absorption ointments

Answer 11

Hydrous, intermediate water affinity, moderate spreadability, poorly washable, drug incorporation are solids/oil/some aqueous incorporations, intermediate drug release, intermediate occlusive. Ex. Lanolin

Question 12

What are the attributes of water-removable ointments?

Answer 12

Hydrous, hydrophilic, easy to spread, washable, drug incorporation is solid/aqueous, fair drug release, not occlusive. Ex. Hydrophilic ointment

Question 13

What are attributes of water-soluble ointments?

Answer 13

Anhydrous/hydrous, hydrophilic, moderate/easy to spread, washable, drug incorporation is solid/aqueous, good drug release, not occlusive. Ex. PEG ointment

Question 14

Explain incorporation in the preparation of ointments

Answer 14

Spatulation with a spatula and a glass or parchment ointment slab is most commonly used. May sometimes use trituration with a mortar and pestle. Incorporating solids usually need to reduce particle size before incorporation to avoid grittiness. Use levigation of the material in a vehicle in which it is not soluble to make a smooth dispersion. Levigating agent must be chemically and physically compatible with the drug and the base. Generally use liquid petrolatum (mineral oil) for bases where external phase oil and glycerin when external phase is aqueous. Levigation may be done using spatulation or trituration.

Question 15

Explain fusion in the preparation of ointments

Answer 15

Some or all of the components are melted together and cooled with stirring until congealed. Ingredient like beeswax, stearyl alcohol or high MW PEG difficult for incorporation technique so fusion is used. Water bath is used to avoid over-heating and material with highest melting temperature melted first followed by next highest melting point. Seldom exceed 70ºC and first melted acts as solvents. Care taken with heat-liable or volatile ingredients. If aqueous and oleaginous mixture, heat separately and add ingredients to appropriate phase. Combine with stirring and usually aqueous portion added to oleaginous portion

Question 16

Besides ointments, what are some topical semisolid dose forms?

Answer 16

Creams, lotions and gels, pastes, plasters and glycerogelatins

Question 17

Describe creams

Answer 17

Semisolid preparations usually containing medication and in an emulsion (o/w) base. Water evaporates and leaves oleaginous film. Cosmetically acceptable as not greasy and easy to spread and remove. Many products are marketed both as cream and ointment dose forms. Ointment when occlusion needed as skin dry and scaly. Creams when drying needed and skin is weeping or has exudates. Occasionally creams are used but covered with occlusive dressing

Question 18

Describe lotions and gels

Answer 18

Lotions may be emulsions or fine suspensions and often formulated as semi-liquid creams
Gels provide a useful vehicle for some medications and have been discussed

Question 19

Describe pastes

Answer 19

Stiff preparations with a high content of solid material often to 25%. Prepared by incorporation or fusion and if levigating agent required, use portion of base as quantity may be large. Used as protectants and to absorb secretions. Products like zinc oxide paste USP may be used for conditions like diaper rash

Question 20

Describe plasters and glycerogelatins

Answer 20

Plasters designed for long-term application to skin. Usually have fabric or paper backing. Archaic products seldom used any more. Exception is the corn plaster which usually contains the keratolytic salicylic acid. Glycerogelatins are melted and painted onto the skin where they solidify. Unna’s booth zinc oxide, calamine, glycerin and gelatin (pressure, varicose veins)