title: Comparative effects of verapamil and isradipine on steady-state digoxin kinetics.
abstract: The effects on the steady-state digoxin pharmacokinetics of verapamil (240 mg/day) and a new dihydropyridine calcium channel blocker, isradipine (15 mg/day), were compared. Nineteen healthy white men, aged 23 to 40 years, ingested 0.25 mg digoxin tablets every 12 hours for two consecutive periods of 2 weeks. Each subject also received one of the calcium channel blockers during one of these periods, with agent and sequence randomized. Analyst-blind RIA serum digoxin determinations demonstrated that the nine subjects who received isradipine, 5 mg t.i.d., had a small increment in peak digoxin level from 2.3 +/- 0.6 to 2.9 +/- 0.7 ng/ml (p less than 0.05) but no significant change in steady-state level or AUC over 12 hours. By contrast, the 10 subjects who received verapamil, 80 mg t.i.d., showed significant increases in steady-state (0.9 +/- 0.1 to 1.3 +/- 0.2 ng/ml; p less than 0.001) and peak serum digoxin concentrations (2.5 +/- 0.7 to 3.6 +/- 0.8 ng/ml; p less than 0.001) and in AUC (15.7 +/- 1.7 to 23.6 +/- 2.9 ng . hr/ml; p less than 0.001). Neither calcium channel blocker reduced renal digoxin clearance. Verapamil increases digoxin levels without affecting renal clearance. Isradipine has no clinically important interaction with digoxin.
authors.affiliation: Division of Clinical Pharmacology, University of Massachusetts Medical Center, Worcester 01655.
authors.forename: S M
authors.initials: SM
authors.lastname: Rodin
authors.forename: B F
authors.initials: BF
authors.lastname: Johnson
authors.forename: J
authors.initials: J
authors.lastname: Wilson
authors.forename: P
authors.initials: P
authors.lastname: Ritchie
authors.forename: J
authors.initials: J
authors.lastname: Johnson
mesh_terms: D000328:Adult; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004077:Digoxin / Q000493:pharmacokinetics*; D004347:Drug Interactions; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D017275:Isradipine; D008297:Male; D011725:Pyridines / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D002121:Calcium Channel Blockers; D011725:Pyridines; D004077:Digoxin; D014700:Verapamil; D017275:Isradipine