Pharmacokinetic interaction between domperidone and ketoconazole leads to QT prolongation in healthy volunteers: a randomized, placebo-controlled, double-blind, crossover study

AIMS To assess the steady-state pharmacokinetic and QTc effects of domperidone and ketoconazole, given alone and together. METHODS A randomized, placebo-controlled, double-blind, crossover study was carried out. Healthy subjects (14 men, 10 women; age 18-39 years; mean weight 73.5 kg, range 53.8-98.8 kg; 23 Europid, 1 Afro-Caribbean) received orally, for 7 days each, placebo, domperidone 10 mg, four doses daily, at 4 h intervals, ketoconazole 200 mg 12-hourly and domperidone and ketoconazole together. The washout period was 15 days. Pharmacokinetics and serial 12-lead ECGs were assessed on day 7, and serial ECGs on day -1 and at follow-up. Two subjects withdrew before the third treatment period, so data were available for 22-24 subjects. RESULTS Ketoconazole tripled domperidone concentrations at steady-state. Domperidone, ketoconazole and their combination significantly increased QTcF in men. Overall adjusted mean differences from placebo were 4.20 (95% CI 0.77, 7.63), 9.24 (95% CI 5.85, 12.63) and 15.90 (95% CI 12.47, 19.33) ms, respectively. In women, QTcF was not significantly different from placebo on either domperidone or ketoconazole alone, or in combination. However, QTc was positively correlated with plasma drug concentrations, in both men and women. DQTcF increased by about 2ms per 10 ng ml-1 rise in domperidone concentration, and per 1 mgml-1 rise in ketoconazole concentration. CONCLUSIONS Ketoconazole tripled the plasma concentrations of domperidone. Domperidone and ketoconazole increased QTcF in men, whether given together or separately. The effect of domperidone alone was below the level of clinical importance. The negative result in women is unexplained.