Rosiglitazone does not affect the steady-state pharmacokinetics of digoxin

Rosiglitazone is a potent insulin-sensitizing oral hypoglycemic agent of the thiazolidinedione class that works through activation of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) nuclear receptor and improves glycemic control in patients with non-insulin-dependent diabetes mellitus. The potential for a drug-drug interaction with oral digoxin was investigated. Subjects received both of the study regimens in a random sequence: digoxin 0.375 mg plus matching placebo for rosiglitazone orally each morning for 14 days or digoxin 0.375 mg plus 8 mg rosiglitazone orally each morning for 14 days. There was a 14-day washout period between sessions. Blood and urine were collected over 24 hours beginning on the morning of day 14 for measurement of digoxin concentrations. An equivalence statistical approach was used, with rosiglitazone considered to have no effect on the pharmacokinetics of digoxin if the 90% confidence interval (CI) for the ratio of digoxin plus rosiglitazone relative to digoxin plus placebo was completely contained within the range (0.80, 1.25) for the primary end points, AUC(0-24), and C24. Digoxin AUC(0-24) and C24 values were similar for digoxin 0.375 mg plus matching placebo (18.5 ng.h/mL and 0.579 ng/mL, respectively) and digoxin 0.375 mg plus rosiglitazone (19.1 ng.h/mL and 0.594 ng/mL, respectively). Point estimates were 1.05 (90% CI: 1.01, 1.10) for AUC(0-24) and 1.04 (90% CI: 0.98, 1.11) for C24. Oral and renal clearance were also similar between regimens. Digoxin alone or in combination with rosiglitazone was safe and well tolerated. The most common adverse experience was headache. Coadministration of digoxin with rosiglitazone had no significant effect on the safety or steady-state pharmacokinetics of digoxin.