Disclosed herein is a method for the production of disulfide compounds of the formula I PAC-SA—SB—R*  (I) wherein PAC-SA is a residue of a pharmaceutically active drug a metabolite thereof or a pharmaceutically acceptable salt thereof that is covalently bonded via the sulfur atom, SA of a reduced sulfhydryl, sulfinyl, sulfonyl or sulfonamide group to the sulfur atom SB of an oxidized sulfhydryl group of a pharmacologically acceptable sulfhydryl compound in the absence of an acid. Preferably the pharmaceutically active drug is a proton pump inhibitor and the sulfhydryl compound is N-acetyl cysteine. The disulfide compounds according to the invention can be prepared either in vitro or in vivo and are stable in the acidic conditions of the stomach. Pharmaceutical compositions containing compounds of the formula I and a method for the treatment or prophylaxis of gastrointestinal disorders using compounds of the formula I are also described.