Microemulsion compositions

A pharmaceutical composition that is an oil-in-water microemulsion, comprising:

• a) a lipid phase comprising an oily component and one or more surfactant(s) and, one or more co-surfactant(s);
• b) an aqueous phase comprising one or more surfactant(s), and one or more co-surfactants;
• and
• c) a pharmaceutically active compound, wherein:
• the weight/volume ratio between the total amount of surfactant and co-surfactant in the lipid phase to the total amount of surfactant and co-surfactant in the aqueous phase is from 2 to 10;
• the weight/volume ratio between the amount of oily component in the lipid phase to the total amount of surfactant and co-surfactant in the aqueous phase is from 0.2 to 1.0;
• and
• in the resulting oil-in-water microemulsion, the average particle size is less than 30 nm.