What antiemetic can help with post-operative nausea and vomiting (PONV)?

Antiemetics for Postoperative Nausea and Vomiting (PONV)

For PONV prophylaxis, use combination therapy with ondansetron 4 mg IV plus dexamethasone 4-5 mg IV administered before the end of surgery, as this provides superior prevention compared to either agent alone. 1

First-Line Prophylactic Regimen

The optimal prophylactic approach combines ondansetron 4 mg IV with dexamethasone 4-5 mg IV, administered before the end of surgery. 1 This dual-agent strategy is recommended by the American Society of Anesthesiologists and provides approximately 25% relative risk reduction per agent, with combination therapy significantly improving efficacy. 1

Specific Agent Evidence:

5-HT3 Antagonists:

• Ondansetron 4 mg IV is the most extensively studied agent, reducing postoperative vomiting and rescue antiemetic use. 2, 3
• The FDA label confirms that ondansetron 4 mg prevents postoperative vomiting in 79% of patients versus 63% with placebo (P <0.001), with no additional benefit from 8 mg dosing. 3
• Other effective 5-HT3 antagonists include granisetron, tropisetron, and ramosetron. 2

Corticosteroids:

• Dexamethasone 4-5 mg IV reduces PONV incidence in the first 24 hours and decreases rescue antiemetic needs for up to 72 hours. 1
• Doses below 4 mg are less effective and should be avoided. 1

Dopamine Antagonists:

• Droperidol effectively reduces postoperative nausea, vomiting, and rescue antiemetic use. 2
• Haloperidol is effective for reducing postoperative nausea, vomiting, and rescue antiemetic use. 2
• Metoclopramide 10 mg shows efficacy in reducing vomiting during the first 24-hour postoperative period. 2

Anticholinergics:

• Transdermal scopolamine reduces nausea and vomiting, particularly effective for postoperative (not intraoperative) PONV. 2

Risk-Stratified Approach

For patients with ≥2 risk factors (female gender, history of PONV/motion sickness, non-smoking status, use of volatile anesthetics or opioids), add a third antiemetic agent from a different pharmacological class. 1

For high-risk patients (≥3 risk factors) who fail standard dual prophylaxis, consider adding olanzapine 10 mg to the ondansetron-dexamethasone combination, which reduces PONV incidence from 63% to 26% in the first 24 hours (RR 0.40,95% CI 0.21-0.79, p=0.008). 4

Multimodal Strategy for Cesarean Delivery

For cesarean delivery under regional anesthesia, use a multimodal approach combining: 2

• Fluid preloading with crystalloid or colloid
• Intravenous ephedrine or phenylephrine to prevent hypotension
• Lower limb compression
• Antiemetic agents (5-HT3 antagonists combined with either droperidol or dexamethasone)

Combination regimens (5-HT3 plus droperidol or dexamethasone) are significantly more effective than 5-HT3 antagonists alone for cesarean delivery patients. 2

Rescue Treatment

If PONV occurs despite prophylaxis, administer a rescue antiemetic from a different pharmacological class than those used for prophylaxis. 1, 5

Ondansetron 4 mg IV is effective as rescue treatment for established PONV during recovery. 2, 3

Metoclopramide 10-20 mg oral or IV can be used as rescue therapy, particularly if gastric stasis is suspected, with efficacy especially within the first 24 hours postoperatively. 2, 5

For patients who received 5-HT3 antagonists prophylactically, switch to a dopamine antagonist (metoclopramide 20 mg oral or prochlorperazine 10 mg oral/IV) for rescue. 5

Important Note on Repeat Dosing:

In patients who do not achieve adequate control after a single prophylactic dose of ondansetron 4 mg, administering a second postoperative dose of ondansetron 4 mg does not provide additional control. 3 Switch to a different drug class instead.

Pediatric Dosing

For pediatric patients (aged 2-12 years): ondansetron 0.1 mg/kg IV (maximum 4 mg) administered over at least 30 seconds immediately prior to or following anesthesia induction. 3

For infants (1-24 months): ondansetron 0.1 mg/kg IV within 5 minutes following induction of anesthesia reduces vomiting from 28% (placebo) to 11% (P ≤0.01). 3

Critical Pitfalls to Avoid

• Do not use single-agent prophylaxis in high-risk patients—it is insufficient. 1
• Do not underdose dexamethasone—doses below 4 mg are less effective. 1
• Do not repeat ondansetron if the first dose fails—switch to a different drug class. 3
• Exercise caution with metoclopramide in elderly patients—monitor for extrapyramidal side effects. 5
• Reduce metoclopramide dose in renal impairment—clearance correlates with creatinine clearance. 5
• Consider potential immunosuppressive effects of dexamethasone in cancer surgery—long-term oncological outcomes remain unknown. 1