title: Stereoselective interaction between piroxicam and acenocoumarol.
abstract: 1. An open-label study was performed to assess the effect of piroxicam on the pharmacokinetics of acenocoumarol enantiomers. 2. Eight healthy male volunteers received an oral dose of 4 mg rac-acenocoumarol on days 1 and 8, plus 40 mg piroxicam orally 2 h before the anticoagulant on day 8. R- and S-acenocoumarol, piroxicam and their metabolites were measured in plasma over a 24 h interval. 3. The pharmacokinetics of R-acenocoumarol were markedly modified by piroxicam: Cmax+28.0% (s.d.23.8), P < 0.05; AUC(0, 24 h)+47.2% (21.5), P < 0.005; and t1/2 +38.0% (34.5), P < 0.01. A concomitant decrease of CL/F was observed: -30.8% (10.0), P < 0.0001. A similar, but statistically non-significant trend, was observed on the S-enantiomer: Cmax: +9.5% (s.d.36.6), AUC(0, 24 h): + 15.4% (23.4), t1/2: +19.9% (42.0), and CL/F: -9.8% (20.5). V/F remained unchanged for both enantiomers. 4. Piroxicam plasma AUC(0, 24 h) correlated closely with R- and S-acenocoumarol AUCs on day 1 (r = 0.901, P < 0.005 and r = 0.797, P < 0.05, respectively), as well as with the difference of AUC between days 1 and 8 for R-acenocoumarol (r = 0.903, P < 0.001) and S-acenocoumarol (r = 0.711, P < 0.05). 5. Piroxicam markedly reduced acenocoumarol enantiomer clearance, with a greater effect on the more active R-isomer. This interaction, which occurs in addition to the well documented pharmacodynamic one (effect on platelets), is expected to result in increased anticoagulant effect.
authors.affiliation: Division of Clinical Pharmacology, University Hospitals, Geneva, Switzerland.
authors.forename: P
authors.initials: P
authors.lastname: Bonnabry
authors.forename: J
authors.initials: J
authors.lastname: Desmeules
authors.forename: S
authors.initials: S
authors.lastname: Rudaz
authors.forename: T
authors.initials: T
authors.lastname: Leemann
authors.forename: J L
authors.initials: JL
authors.lastname: Veuthey
authors.forename: P
authors.initials: P
authors.lastname: Dayer
mesh_terms: D000074:Acenocoumarol / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D000284:Administration, Oral; D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D000925:Anticoagulants / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D004347:Drug Interactions; D006801:Humans; D008297:Male; D010894:Piroxicam / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D013237:Stereoisomerism
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000925:Anticoagulants; D010894:Piroxicam; D000074:Acenocoumarol