A double-blind, randomized, crossover study assessed the effects of a single 40-mg dose of fluvastatin on the steady-state pharmacokinetics of digoxin in chronically treated patients. After demonstrating consistent digoxin serum concentrations as part of the inclusion criteria, 18 patients received a single dose of either fluvastatin or placebo, with a 1-week washout period between crossover to the other treatment. For each patient, 14 serum samples were drawn and urine collected over 24 hours; all samples were assayed for digoxin using a fluorescence polarization immunoassay. The following pharmacokinetic parameters were determined using noncompartmental techniques: area under the curve for 24 hours (AUC24); time to maximum concentration after digoxin (tmax); maximum concentration after digoxin dosing (Cmax); concentration at 24 hours after fluvastatin or placebo (Cmin); total amount excreted in the urine over 24 hours (U24); and urinary clearance (Clren). The pharmacokinetic data were analyzed for sequence, patient nested with sequence, and period and treatment differences using ANOVA, Schuirmann's two one-sided testing approach, confidence intervals, and power analysis. The AUC24, Cmax, and tmax for digoxin were considered bioequivalent with the two treatments. The differences in Cmax, U24, and Clren were statistically significant but were not considered to be clinically relevant due to the low magnitude of the difference (< 20%). There were no clinically significant adverse reactions attributable to either digoxin or fluvastatin.