Abstract: A pharmaceutical composition for the prevention of sexually transmitted diseases, intended to be contacted with a mucosa. The composition contains, on the one hand, at least one constituent active against the viruses and bacteria responsible for the said sexually transmitted diseases and, on the other hand, a product inhibiting the penetration of the active constituent across a mucosa, in combination with a pharmaceutically acceptable vehicle adapted to the topical administration of this composition. Advantageously, the product inhibiting penetration is a film-former capable of forming a film with which the active constituent or constituents are associated.