title: Lack of interaction between tramadol and coumarins.
abstract: The objective of this study was to investigate whether the central analgesic tramadol influences the effects of the coumarin anticoagulant phenprocoumon during multiple-dose administration. Nineteen patients receiving long-term anticoagulant therapy who had been in a stable hypothrombinemic state for at least 3 months completed a double-blind, placebo-controlled, crossover study. Tramadol was administered in the usual therapeutic dose of 50 mg three times daily. The average daily phenprocoumon dose was identical for individual patients in both treatment periods. The equivalence ratio (tramadol/placebo) of the international normalized ratio (INR) values was 0.99 (90% confidence interval 0.89-1.10), thus fulfilling predetermined bioequivalence criteria (0.70-1.43). Therefore, tramadol does not affect INR in patients being treated with phenprocoumon. These data suggest a lack of interaction between tramadol and coumarin anticoagulants.
authors.affiliation: Centre for Human Drug Research, Leiden University, The Netherlands.
authors.forename: J K
authors.initials: JK
authors.lastname: Boeijinga
authors.forename: E
authors.initials: E
authors.lastname: van Meegen
authors.forename: R
authors.initials: R
authors.lastname: van den Ende
authors.forename: C E
authors.initials: CE
authors.lastname: Schook
authors.forename: A F
authors.initials: AF
authors.lastname: Cohen
mesh_terms: D000368:Aged; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000704:Analysis of Variance; D000925:Anticoagulants / Q000008:administration & dosage / Q000494:pharmacology*; D001682:Biological Availability; D016001:Confidence Intervals; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010644:Phenprocoumon / Q000008:administration & dosage / Q000494:pharmacology*; D014147:Tramadol / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000701:Analgesics, Opioid; D000925:Anticoagulants; D014147:Tramadol; D010644:Phenprocoumon