A pharmaceutical composition for topical administration, including, as the pharmaceutically active component, at least 5% by weight, based on the total weight of the composition of a piperidinopyrimidine derivative or a pharmaceutically acceptable salt thereof; an acid in an amount to completely solubilise the piperidinopyrimidine derivative or a pharmaceutically acceptable salt thereof; a solvent composition including at least two of water, a lower alcohol and a co-solvent selected from one or more of the group consisting of aromatic and polyhydric alcohols; wherein when the co-solvent includes propylene glycol, it is present in an amount of less than approximately 10% by weight.