There is provided pharmaceutical compositions for the treatment of e.g. opioid dependency comprising microparticles of a pharmacologically-effective amount of buprenorphine, or a pharmaceutically-acceptable salt thereof, in associative admixture with particles comprising a weak acid, or particles comprising weakly-acidic buffer forming materials. The composition may further comprise a disintegrant and/or particles of a pharmacologically-effective amount of naloxone, or a pharmaceutically-acceptable salt thereof. The compositions are useful in the treatment of opioid dependency/addiction and/or pain.