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

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 3.7-397.6) were characteristic of the PT-INR increased group. These results suggest that tramadol coadministration enhanced the antithrombotic effects of warfarin in patients with higher PT-INR, lower albumin levels and decreased renal function as the risk factors for this drug interaction.

Assessment of clonidine orally disintegrating tablet for pre-anesthetic medication in pediatric surgery.

The purpose of this study is to assess orally-disintegrating (OD) tablet of clonidine hydrochloride (CL) for a pre-operative sedation in pediatric surgery. Sedation score and plasma CL concentration of OD formulation was compared with original preparation, CL lollipop, in pediatric patients. Fourteen patients (age: 3.9+/-2.3 years, weight: 16.9+/-5.0 kg) for OD group and 9 patients (age: 4.4+/-3.1 years, weight: 17.2+/-7.0 kg) for lollipop group received 4 microg/kg of CL preparation. Pre-operative sedation was evaluated by 5-point scoring systems at entering the operating room. Plasma CL concentrations were determined 120 min after administration of CL preparation. The changes in systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were also assessed before and after administration of CL preparation. Every patient in OD group had satisfactory sedation (sedation score: 2 and 3), whereas, 3 (33%) in lollipop group had unsatisfactory sedation (sedation score: 0 and 1). Plasma CL concentration in OD group was significantly higher than those in lollipop group (0.75+/-0.15 vs. 0.42+/-0.21 ng/ml, p<0.01). There was no significant difference in hemodynamic parameters (SBP, DBP and HR) between before and after administration of CL preparation in both OD and lollipop group. We conclude that OD is superior preparation of CL for pre-operative sedation in pediatric surgery.