Methaqualone Warfarin

Methaqualone may cause a very small and clinically unimportant reduction in the anticoagulant effects of warfarin. 

The average prothrombin time of 10 patients stabilised on warfarin was 20.9 seconds before, 20.4 seconds during, and 19.6 seconds after taking methaqualone 300 mg at bedtime for 4 weeks. The plasma warfarin levels of another patient were unaffected by methaqualone, although there was some evidence that enzyme induction had occurred. Methaqualone has some enzyme-inducing effects so that any small changes in prothrombin times reflect a limited increase in the metabolism and clearance of warfarin, but these appear to be too small to be of clinical significance. No special precautions seem to be necessary. 

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