Ranitidine, at blood levels produced by standard recommended doses, does not inhibit the hepatic cytochrome P450-linked mixed function oxygenase system. Accordingly, Ranitidine in usual therapeutic doses does not potentiate the actions of drugs which are inactivated by this enzyme; these include diazepam, lignocaine, phenytoin, propranolol, theophylline and warfarin. There is no evidence of an interaction between Ranitidine, amoxicillin and metronidazole. If high doses (2 g) of sucralfate are co-administered with ranitidine, the absorption of the latter may be reduced. This effect is not seen if sucralfate taken after an interval of 2 hours.