Dimenhydrinate and metoclopramide alone or in combination for prophylaxis of PONV

Dimenhydrinate and metoclopramide are inexpensive antiemetic drugs. Metoclopramide, especially, has been studied extensively in the past, but there are no studies on the combination of both drugs for prevention of postoperative nausea and vomiting (PONV).

One hundred and sixty male inpatients undergoing endonasal surgery were randomized to receive one of four antiemetic regimens in a double-blind manner: placebo, 1 mg x kg(-1) dimenhydrinate, 0.3 mg x kg(-1) metoclopramide, or the combination of both drugs was administered after induction of anesthesia. Patients received a second dose of these drugs six hours after the first administration to mitigate their short half-life. Standardized general anesthesia included benzodiazepine premedication, propofol, desflurane in N2O/O2 vecuronium, and a continuous infusion of remifentanil. Postoperative analgesia and antiemetic rescue medication were standardized. Episodes of vomiting, retching, nausea, and the need for additional antiemetics were recorded for 24 hr. The incidences of PONV were analyzed with Fisher's Exact test and the severity of PONV (rated by a standardized scoring algorithm) with the Jonckheere-Terpestra-test.

The incidence of patients free from PONV was 62.5% in the placebo-group and increased to 72.5% in the metoclopramide-group (P = 0.54), 75.0% in the dimenhydrinate-group (P = 0.34), and 85.0% in the combination- group (P = 0.025). In the latter group, the severity of PONV was reduced compared with placebo treatment (P = 0.017; Jonckheere-Terpestra-test).

Dimenhydrinate and metoclopramide were ineffective in reducing the incidence and the severity of PONV. Their combination reduced the incidence of PONV compared with placebo.