Inhibition of epidural morphine-induced pruritus by intravenous droperidol

Our objective was to study in more detail our previous finding that intravenous droperidol inhibits pruritus induced by epidural morphine.

In a double blind study, 107 ASA I or II patients undergoing cesarean section received epidural anesthesia with 150 mg (30 ml) of 0.5% bupivacaine with 1:200,000 epinephrine and 2 mg of morphine hydrochloride in a single injection. They were randomly allocated to either receive (treated group, n = 54) or not receive (control group, n = 53) an intravenous injection of 2.5 mg of droperidol just after delivery. During the postoperative period, the patients were assessed for the occurrence and severity of pruritus or other possible untoward symptoms. Pruritus was classified as absent, mild, moderate, or severe.

The incidence of pruritus in control group was absent, 26.4%; mild, 39.6%; moderate, 28.3%; severe, 5.7%; for the treated group, the incidences were, respectively: 59.2; 27.8; 13.0; and 0.0% (p = 0.0003; Mann-Whitney test). As for other side effects of morphine, nausea and vomiting had a similar incidence in the two groups; urinary retention could not be analyzed because of bladder catheterization, and constipation, herpes labialis and clinical evidence of respiratory depression were never observed. Droperidol produced a greater incidence of somnolence (2% in control and 17% in treated group--p < 0.02; Fisher's exact test), but it was never incapacitating. The incidence of hypotension was similar in the two groups.

Intravenous droperidol reduces the incidence and severity of pruritus caused by epidural injection of morphine without inducing important side effects.