Stability of EmulsionPhysical Pharmacy

Emulsion is considered to be physically unstable if:a) the internal or dispersed phase upon

standing tends to form aggregates of globules,

Flocculation

good emulsion flocculation

b) large globules or aggregates of globules rise to the top or fall to the bottom of the emulsion to form a concentrated layer of the internal phase,

Creaming

or

rise fallgood emulsion

c) if all or part of the liquid of the internal phase separates and forms a distinct layer on the top or bottom of the emulsion as a result of the coalescing of the globules of the internal phase.

Coalescence

good emulsion coalescence

Bioavailability of Emulsion

Physical Pharmacy

Bioavailability- the fraction of the administered dose that

reaches the systemic circulation

1. Oil-in-water (O/W)- oil is a dispersed phase & an aqueous

solution is the continuous phase

2 of simple emulsion

e.g. Mineral oilMilk

Oil-soluble vitaminsVegetative oils

Preparations for enteral feeding

2. Water-in-oil (W/O)- water or an aqueous solution is the

dispersed phase & oil or oleaginous material is the continuous phase

e.g.

MayonnaiseMargarine

Drug administered by P.O.

Griseofulvin- are prepared in the form of an O/W

emulsion, used to treat fungal infections of the skin & nail fungus

Systemic Circulation

stomach intestines liverlose drug lose drug

lose drug

Bioavailabily generally decreases (due to incomplete absorption)

Drug administered by I.V.

Diprivan Injectable Emulsion (AstraZeneca)

Systemic Circulation

- help relax before and during general anesthesia for surgery or other medical procedures

Bioavailability is 100%

factors that affects the bioavailability of emulsions:viscositySurface tensionSolubility Particle size Complexation Excipients