The present invention provides pharmaceutical compositions for topical delivery comprising a suitable carrier and a codrug capable of penetrating, or being transported across, the dermis. The codrug according to the invention comprises a first constituent moiety linked to a second constituent moiety, wherein the second constituent moiety is the same as, or different from, the first constituent moiety. The first and second constituent moieties are so linked that they are easily transported into or across the dermis, into the skin, or into the blood or lymphatic system, and are reconstituted in vivo to form the first and second constituent moieties.