Supersaturated topical compositions

A two-phase composition for topical application, wherein the two phases are intended to be mixed together on or immediately prior to application, comprising:

• a first, non-aqueous liquid phase containing a drug dissolved therein and comprising a topically acceptable non-aqueous and non-volatile solubiliser;
• and a second, non-aqueous liquid phase, physically and/or chemically different from the first phase but miscible therewith on admixture, optionally containing the same drug dissolved therein and comprising a topically acceptable non-aqueous and non-volatile carrier;
• the composition of the first and second liquid phases being such that each has a different lipophilicity and each confers a different saturated solubility on the drug;
• the concentration of drug in each phase in which it is present and the composition of each of the first and second liquid phases being such that, on admixture of the phases, the total drug concentration in the mixture thus formed is greater than the saturated drug concentration in the same mixture, whereby the said mixture is supersaturated with the drug and wherein the composition further comprises a volatile solvent in each of the first and second liquid phases, whereby on admixture of the phases, the rate of loss of volatile solvent originally present in the first liquid phase is comparable to the rate of loss of volatile solvent originally present in the second liquid phase, such that the ratio of the total drug concentration in the mixture to the saturated drug concentration in the same mixture remains substantially constant.