OPIOIDS AND WARFARIN AND OTHER ORAL ANTICOAGULANTS

Tramadol has been reported to increase the anticoagulant effects of warfarin and phenprocoumon in a few patients. Similarly, several patients taking warfarin have shown a marked increase in prothrombin times and/or bleeding when given co-proxamol (which contains dextropropoxyphene (propoxyphene)), but the inter- action seems to be uncommon.
It would be prudent to consider monitoring prothrombin times in any patient taking anticoagulants when tramadol is first added, being alert for the need to reduce the anticoagulant dosage.