Dosage Form

Definition

Appearance

Formulation

Rheology

Gel

A usually translucent, non-greasy emulsion or suspension semisolid dosage form for external application to the skin, which contains a gelling agent in quantities sufficient^a to impart a three-dimensional, cross-linked matrix.  A gel provides a cooling sensation when applied to the skin.

Thick or thin, usually translucent; holds a stiff or soft peak when a drop is placed on a flat surface.

Usually hydrophilic, and contains sufficient^a quantities of a gelling agent such as starch, cellulose derivatives, carbomers, magnesium-aluminum silicates, xanthan gum, colloidal silica, aluminum or zinc soaps.

Lotion

An opaque, thin, non-greasy emulsion liquid dosage form for external application to the skin, which generally contains a water-based vehicle with > 50% of volatiles^c and sufficiently low viscosity that it may be delivered by pouring.  A lotion tends to evaporate rapidly with a cooling sensation when rubbed onto the skin.

Thin, opaque; holds no peak when a drop is placed on a flat surface.

Usually hydrophilic, and contains > 50% of volatiles as measured by LOD (loss on drying).^c

< 30,000 cps^d

Cream

An opaque, viscous, non-greasy to mildly greasy emulsion or suspension semisolid dosage form for external application to the skin, which contains < 50% of hydrocarbons or polyethylene glycols as the vehicle and/or > 20% of volatiles.^c  There are two types of creams: a hydrophilic cream with water as the continuous phase and a lipophilic cream with oil as the continuous phase  A cream tends to mostly evaporate or be absorbed when rubbed onto the skin.

Thick, opaque; holds a soft to stiff peak when a drop is placed on a flat surface.

Hydrophilic creams^b have water (the aqueous phase) as the continuous phase.  They contain oil-in-water emulsifying agents such as sodium or trolamine soaps, sulfated fatty alcohols, polysorbates and polyoxyl fatty acid and fatty alcohol esters combined, if necessary, with water-in-oil emulsifying agents.

Lipophilic creams^b have oil (the lipophilic phase) as the continuous phase.  They contain water-in-oil emulsifying agents such as wool alcohols, sorbitan esters and monoglycerides. 

> 30,000 cps^d

Ointment

An opaque or translucent, viscous, greasy emulsion or suspension semisolid dosage form for external application to the skin, which generally contains a > 50% of hydrocarbon-based or a polyethylene glycol-based vehicle and < 20% of volatiles.^c  An ointment tends not to evaporate or be absorbed when rubbed onto the skin.

Thick, translucent or opaque; holds a stiff peak when a drop is placed on a flat surface.

Usually lipophilic, and contains > 50% of hydrocarbons or polyethylene glycols as the vehicle and < 20% of volatiles as measured by LOD.

Paste

An opaque, viscous, greasy to mildly greasy semi-solid dosage form for external application to the skin, which contains a large proportion (i.e., 20-50%) of solids finely dispersed in an aqueous or fatty vehicle.  A paste adheres well to the skin, forming a protective layer.

Very thick, opaque; holds a stiff peak when placed on a flat surface.

Contains a large proportion (20-50%) of dispersed solids in a fatty or aqueous vehicle.