The influence of propofol on vomiting induced by apomorphine.

It has been proposed that propofol has antiemetic effects even in nonsedative doses. The aim of this study was to investigate whether propofol influences vomiting induced by the dopamine agonist apomorphine. Ten healthy male volunteers received apomorphine infusion (1 mg/min) until vomiting was induced on four different occasions in a randomized order: a) during propofol infusion (2.4 +/- 0.7 mg.kg-1.h-1, mean +/- SD) at a sedation score of Grade 2-3 on a 5-grade scale; b) during midazolam infusion (0.13 +/- 0.04 mg.kg-1.h-1) at a sedation score of Grade 2-3 on a 5-grade scale; c) after a single nonsedating bolus dose propofol 0.4 mg/kg; and d) during infusion of normal saline. The amount of apomorphine needed to induce vomiting was increased after sedation with propofol (P = 0.005) as well as midazolam (P = 0.001). There was no difference in the sensitivity to apomorphine between these sedative regimens. The nonsedating single bolus propofol did not change the sensitivity to apomorphine compared to the saline infusion. We conclude that propofol given in a nonsedative dose has no effect on apomorphine-induced vomiting. However, the total amount of apomorphine given to induce vomiting was significantly larger during propofol sedation than during saline infusion. This was probably an effect of sedation inasmuch as a similar result was achieved during midazolam sedation.