Comparison of the antiemetic effect of high-dose intravenous metoclopramide and high-dose intravenous haloperidol in a randomized double-blind crossover study.

Metoclopramide is an effective antiemetic for cisplatin-induced vomiting when given in parenteral high-dose regimens but not oral low-dose regimens. Metoclopramide was compared to haloperidol, also given in a high-dose parenteral regimen. Patients received two cycles of cisplatin at a dose greater than or equal to 70 mg/m2. Metoclopramide (2 mg/kg intravenous) was given every two hours for five doses beginning one half hour before cisplatin. Haloperidol (3 mg intravenous) was given on the same schedule. A randomized double-blind crossover design was used to control subjective bias and to compare the same patient's experiences. Twenty-eight patients completed both study arms. Excellent control of vomiting was achieved with both drugs. Metoclopramide resulted in 1.92 vomiting episodes (range, 0-5) with 36% having no vomiting. Haloperidol resulted in 3.04 vomiting episodes (range, 0-8) with 20% having no vomiting. Significantly fewer vomiting episodes were noted with metoclopramide rho = .006, paired sign test). However, responses to the two drugs were well correlated (Spearman's rho = .39, P = .03). Metoclopramide and haloperidol are both excellent antiemetics when given in sufficient dosage by an effective route. Metoclopramide does show a mild advantage. However, the positive correlation in response to these agents suggests a common mechanism of action. The ability to identify related antiemetics will be useful in the design of rational combination antiemetic therapy.