title: Pharmacokinetic study of the digoxin-acenocoumarol interaction in rabbits.
abstract: A study was carried out to evaluate the potential pharmacokinetic interaction between digoxin and acenocoumarol. The binding of digoxin to rabbit cardiac tissue homogenates was assessed in vitro, using the equilibrium dialysis technique. An increase in the first-order constant (p<0.05) and a reduction in the partition coefficient in the equilibrium situation (p<0.001) of digoxin were observed when the cardiac homogenates were previously treated with acenocoumarol. In the in vivo study, the kinetics of digoxin administered in single and multiple dosage regimens were compared in control rabbits and in rabbits treated simultaneously with acenocoumarol. Kinetic analysis of the results was performed using Non-linear Mixed Effects Modeling (NONMEM). In the presence of acenocoumarol, the population distribution volume (Vd) of digoxin was increased by 40-60%, no differences being found as regards the elimination clearance. Also, joint administration of both drugs led to a reduction in digoxin concentrations in the heart (p<0.01) at the end of the dosage regimen. Both sets of results point to the hypothesis of a hitherto unreported possible pharmacokinetic interaction between the two drugs affecting the distribution process. This interaction could lead to lower plasma digoxin levels, in view of the increased Vd, and a possible reduction in the therapeutic effect, owing to the decrease in affinity and in concentration in heart tissue.
authors.affiliation: Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Salamanca, Campus Unamuno, 37007 Salamanca, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Martin-Suarez
authors.forename: Drury Rudolph
authors.initials: DR
authors.lastname: Atencio
authors.forename: Francisco González
authors.initials: FG
authors.lastname: Lopez
authors.forename: María
authors.initials: M
authors.lastname: Santos
authors.forename: Aránzazu
authors.initials: A
authors.lastname: Zarzuelo
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Mendez
authors.forename: Ignacio
authors.initials: I
authors.lastname: Alberca
authors.forename: José Martínez
authors.initials: JM
authors.lastname: Lanao
mesh_terms: D000074:Acenocoumarol / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D000818:Animals; D001667:Binding, Competitive; D004077:Digoxin / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D017711:Nonlinear Dynamics; D011817:Rabbits; D014018:Tissue Distribution
chemical_list: D004077:Digoxin; D000074:Acenocoumarol