Abstract: Process for the preparation of N-methylnaltrexone bromide, wherein a compound of the general formula (I): wherein X? represents an anion other than the bromide anion, and R represents hydrogen or a leaving group, is dissolved or dispersed in a suitable polar solvent, the solution or dispersion is mixed with a compound containing bromide anions, and the resulting reaction mixture is stirred until N-methylnaltrexone bromide has formed and crystallized, wherein, in the case where R represents a leaving group, that group is removed during or after the reaction.

Abstract: Process for the preparation of N-methylnaltrexone bromide, wherein a compound of the general formula (I): wherein X? represents an anion other than the bromide anion, and R represents hydrogen or a leaving group, is dissolved or dispersed in a suitable polar solvent, the solution or dispersion is mixed with a compound containing bromide anions, and the resulting reaction mixture is stirred until N-methylnaltrexone bromide has formed and crystallised, wherein, in the case where R represents a leaving group, that group is removed during or after the reaction.