Olanzapine Prophylaxis for Opioid-Induced Nausea and Vomiting: A Single-Arm Exploratory Study

Opioid-induced nausea and vomiting (OINV) affects 10%-45.3% of patients during opioid initiation or dose escalation. Although antiemetics are commonly administered when symptoms occur, their efficacy and safety for prophylactic use remain uncertain. Olanzapine, known for its effectiveness in chemotherapy-induced nausea and vomiting, may be a promising candidate for OINV prophylaxis.

This study aimed to evaluate the efficacy and safety of olanzapine in preventing nausea and vomiting during the initiation of opioid therapy.

This single-arm, single-center exploratory study (jRCT 031220008) assessed the efficacy and safety of administering 5 mg of olanzapine daily for five days in cancer patients initiating regular opioid treatment. The primary endpoint was the complete control (CC) rate over five days, defined as no emetic episodes, no need for rescue antiemetics, and minimal nausea (≤3 on an 11-point scale). Key secondary endpoints included the complete response (CR) rate defined as no emesis and no rescue antiemetics and adverse events evaluated using CTCAE ver.5.0. Exact binomial tests were conducted, assuming a 65% efficacy threshold based on prior studies.

Thirty-five patients were enrolled; 34 received treatment and were analyzed. The mean age was 58.8 years, and 45.7% were male. CC was achieved in 79.4% (95% CI: 64.47-89.92, P = 0.0527), and CR in 82.4% (95% CI: 65.47-93.24, P = 0.0390). No emetic events occurred in 85.3% of patients. No serious adverse events were reported.

Olanzapine may be effective and well tolerated for the prevention of OINV in cancer patients. Further confirmative trials are warranted.