Reversible male infertility due to sulphasalazine: studies in man and rat.

Sulphasalazine treatment for inflammatory bowel disease in man causes oligospermia, reduced sperm motility and an increased proportion of abnormal forms. On withdrawal of sulphasalazine these effects are found to be reversible and 15 pregnancies occurred at a median of 2.5 months after stopping sulphasalazine therapy. Seminal plasma concentrations of acid phosphatase fructose and PGE2 as well as the hormone profiles of patients on sulphasalazine for three months were found to be within normal limits. Sulphasalazine fed to male Sprague Dawley rats caused a dose dependent and reversible infertility with a significant reduction in litter size. Rats fed the metabolite sulphapyridine also had a reduced litter size when mated, while those fed the metabolite 5'aminosalicylic acid and a polymer of 5'aminosalicylic acid did not. It seems likely that the sulphapyridine moiety of sulphasalazine is responsible for the infertility seen, the effect being mediated at a late stage in sperm maturation.