CONCOMITANT ADMINISTRATION OF WARFARIN AND TICLOPIDINE MAY BE ASSOCIATED WITH CHOLESTATIC HEPATITIS. IT MAY ALSO AFFECT THE ACTION OF OTHER DRUGS SUCH AS HYPOGLYCEMIC AGENTS AND ANTICONVULSANTS MAY ACCUMULATE IN THE BODY AS A RESULT OF INTERFERENCE WITH EITHER THEIR METABOLISM OR EXCRETION. INTERFERENCE WITH THE COAGULATION PROCESS MAY BE RESPONISBLE FOR THE INCREASED RISK OF HAEMORRHAGE WHEN ASPIRIN, CLOFIBRATE, OR THROID HORMONES ARE USED CONCOMITANTLY WITH ANTICOAGULANTS. NSAIDS INHIBIT PLATELET FUNCTION TO SOME EXTENT AND HAVE AN IRRITANT EFFECT ON THE G.I. TRACT, SO INCREASE THE RISK OF HAEMORRHAGE. ANTIBACTERIALS MAY INTERFERE WITH PLATELET FUNCTION OR WITH THE BACTERIAL SYNTHESIS OF VITAMIN K IN THE G.I. TRACT AND THUS HAVE AN ANTICOAGULANT EFFECT OF THEIR OWN. BARTITURATES SUCH AS PHENOBARBITONE AND PRIMIDONE DIMINISH ITS ACTIVITY AND OTHER COUMARINS THROUGH INICREASED METABOLISM. CARBAMAZEPINE HAS A SIMILAR EFFECT.