Effects of Tramadol Coadministration on Prothrombin Time-International Normalized Ratio in Patients Receiving Warfarin.

Effects of Tramadol Coadministration on Prothrombin Time-International Normalized Ratio in Patients Receiving Warfarin. Yakugaku Zasshi. 2017;137(8):999-1003 Authors: Hosono T, Kondo A, Kambayashi Y, Homma M Abstract  Several case studies have reported a possible drug interaction between warfarin and tramadol where tramadol coadministration enhanced the antithrombotic effects of warfarin. To assess this drug interaction, changes in prothrombin time-international normalized ratio (PT-INR) before and after tramadol coadministration were investigated in patients receiving warfarin. For this study, we examined 54 patients (male/female: 22/32, 68.4±12.7 years) who were being treated with warfarin for deep vein thrombosis, atrial fibrillation, arteriosclerosis obliterans, congestive heart failure, and other vascular diseases. Significant increases in PT-INR were observed 9.5 (1-118) d after coadministration of tramadol (1.81±0.56 vs. 2.47±1.10, p<0.01). Twenty-eight patients (PT-INR increased group) with PT-INR elevation of greater than 0.5 or dose reduction of warfarin after coadministration of tramadol were compared with other groups of patients to find drug interaction risk factors. Logistic regression analysis revealed that lower levels of albumin (3.5 g/dL or less) [odds ratio (OR) 22.1; 95%CI 2.9-169.9]; lower eGFR (50 mL/min or less) (OR 7.7; 95%CI 1.4-42.0); and PT-INR before tramadol coadministration (OR 38.2; 95%CI 3.7-39...
Source: Yakugaku Zasshi : Journal of the Pharmaceutical Society of Japan - Category: Drugs & Pharmacology Authors: Tags: Yakugaku Zasshi Source Type: research