A pharmaceutical dosage form such as a capsule, a conventional or orallydisintegrating tablet capable of delivering a weakly basic, nitrogen (N)-containing selective serotonin 5- HT3 blocking agent having a pKa in the rangeof from about 5 to 14 and a solubility of not more than about 200 ~g/mL at pH6.8 into the body in a sustained-released fashion, suitable for a once-dailydosing regimen, comprises at least one organic acid, which solubilizes saidweakly basic selective serotonin 5-HT3 blocking agent prior to releasing itinto the hostile intestinal environment wherein the blocking agent ispractically insoluble. The unit dosage form may be composed of a multitude ofmulticoated particulates (i.e., immediate-release beads, sustained-releasebeads and/or one or more timed, pulsatile- release bead populations) and isdesigned in such a way that the weakly basic blocking agent and the organicacid do not come into close contact during processing and/or storage therebyavoiding in-situ formation of acid addition compounds while ensuring that theacid is not depleted prior to completion of the drug release.
