A patch formulation for external use where a basic drug, an organic acid and an organic acid salt are combined as essential components is disclosed. The basic drug is preferably in the form of its acid addition salt. The organic acid is preferably a carboxylic acid having carbon atoms of 2 to 7, and more preferably at least one acid selected from the group consisting of acetic, lactic, tartaric, citric, malic, benzoic and salicylic acids. The organic acid salt is preferably a metal salt of a carboxylic acid, and more preferably sodium acetate.
