Ondansetron has been used successfully for prophylaxis
and treatment of intrathecal morphine induced pruritus.
Gabapentin has anxiolytic, antiemetic, antipruritic effects
and has also been shown to potentiate the analgesic
effect of intrathecally or epidurally administered opioids.

Materials and method: We compared the effectiveness of
oral gabapentin with intravenous ondansetron to prevent
incidence of intrathecal morphine induced pruritus. In a
prospective, double-blind study, sixty patients aged 18-65
years with ASA physical status I and II undergoing surgery
under subarachnoid block were randomized to receive
placebo tablets (ondansetron group) or gabapentin 1200
mg (gabapentin group) 2 hours before surgery. Patients
receiving placebo tablets received 8 mg of intravenous
ondansetron and those receiving gabapentin received 4
ml of intravenous normal saline just prior to subarachnoid
block with 3 ml of 0.5% hyperbaric bupivacaine plus 0.2
mg morphine. The incidence, onset, severity, location of
pruritus and incidence of side effects were studied for next
24 hours.

Results The overall incidence of pruritus was
48.3%. The incidence, severity, location of pruritus was
comparable between the two groups. There was significant
difference between the onset of pruritus between groups
(p=0.009). The incidence and grade of nausea vomiting,
requirement of intraoperative sedation was comparable
between groups. The incidence of urinary retention
was significantly high in gabapentin group (p=0.020).
Respiratory depression was observed in one patient.

Conclusion: A single dose of 1200 mg oral gabapentin 2
hours before, is as effective as prophylactic intravenous
ondansetron 8 mg for prevention of intrathecal morphine
induced pruritus.

Keywords: Gabapentin, Ondansetron, Intrathecal morphine, Pruritus