There is provided pharmaceutical compositions for the treatment of pain e.g. short-term pain, which compositions comprise a mixture comprising: (a) microparticles of alfentanil, or a pharmaceutically acceptable salt thereof, which microparticles are presented on the surfaces of larger carrier particles; (b) a water-soluble weak base; and (c) a compound which is a weak acid, which acid is presented in intimate mixture with the microparticles of alfentanil or salt thereof. The composition may further comprise a disintegrant. The acid is preferably citric acid.