Semisolids include , , and

Semisolids:
A system that is not and does not under low shear stress at

Semisolid dosage forms include ointments, creams, pastes, , and .

Semisolid dosage forms can have topical, , , , and applications

Ointment:
Semisolid preparations, incorporated into a specific , intended for external application to the skin or mucous membranes. They usually contain < % water and > % hydrocarbons

Creams:
Semisolid dosage forms that possess a relatively consistency formulated as either water‐in‐oil or oil‐in‐water emulsions. Creams usually contain > % water and volatiles and < % hydrocarbons, or as the vehicle.

Gels:
Semisolid systems consisting of either suspensions made up of small inorganic particles (e.g. ) or large organic molecules (e.g. or natural gums like Tragacanth) interpenetrated by a liquid.

Pastes:
A semisolid dosage form containing a large proportion (‐50 %) of solids dispersed in a .

Collodions:
A thick solution composed of dissolved in a mixture of and .

:
An agent that softens the skin or soothes irritation in skin or mucous membranes.

:
A substance that protects injured or exposed skin surfaces from harmful or annoying stimuli allowing rejuvenation of the skin.

:
Retention of water in the skin by forming a hydrophobic a barrier that prevents moisture evaporation.

:
A substance that causes water to be retained because of its hygroscopic properties.

Desired properties for semisolid bases include chemical and physical , nonreactive and , free of objectionable , nontoxic, nonsensitizing, and nonirritating, and aesthetically appealing.

According to the USP, there are 4 general classes of bases:
-
- (anhydrous, w/o)
- (o/w)
-

:
Hydrocarbon bases that contain emulsifier(s) that form water‐in‐oil emulsions when water or an aqueous solution is added.
Absorbs the highest amount of water.

: Contain water (amount depends on
the base). Add something with high HLP value.

:
The process of reducing particle size of a solid by
triturating or spatulating with a small amount of a viscous liquid or melted base in which the solid is not soluble.

Levigating agents that are somewhat viscous liquids with low surface tension that don't contain water include , , and .

General rule for choosing a levigating agent:
Choose something that is chemically similar to the base.
- for oily bases
- for water-removable bases

Some active ingredients require special levigating agent:
- for Coal Tar
- for Balsam of Peru
- or Fixed Oils for Ichthammol

Some ingredients that have compatibility problems:
- Tween 80 is not compatible with bases
- Castor Oil is not compatible with significant amounts of

Hydrocarbon bases are miscible with most oils but reduces the .

:
- Large amounts of water, and lesser amount of alcohol (dissolves the emulsifier)
- Miscible with most oils, but reduces the viscosity

bases:
- Variable amounts of water and alcoholic solutions
- Easily accept most oils, but viscosity may decrease

bases:
- Limited amounts of water or alcohol, eventually thin out to a lotion
- Some amounts of oil, larger amounts by adding polysorbate 80

bases:
- Very limited amount of water or alcohol without loss of viscosity
- Some oil, with prior levigation with glycerin or propylene glycol

by :
The material is dissolved in a solvent,
The solvent is allowed to evaporate to produce a thin film
Other ingredients are spread on top of this thin film

:
All or some chemicals in the ointment are combined by being melted together and cooled.

For pastes, we don't use a , we use a part of the base.

The issue with pastes and their physical stability is that it could result in

- Are not required to be sterile (except ophthalmic preparations), but there is a microbial count limit

To minimize number of micro-organisms:
- Environmental control
-
-
- Finished product control

Special pharmacopeial standards:
-
- In-vitro release
-

:
Determination of net weight or volume

:
In largemouth jars or metal or plastic tubes

:
Well closed container and cool place.
- Keeps base intact