What medications should be used for prophylaxis and rescue treatment of postoperative nausea and vomiting (PONV) in adult surgical patients?

PONV Medications: Prophylaxis and Rescue Treatment

Prophylaxis Strategy

All adult surgical patients should receive multimodal antiemetic prophylaxis with 2-3 antiemetics regardless of baseline risk, with higher-risk patients receiving 3-4 agents from different drug classes. 1, 2

Risk Assessment

• Use the Apfel score to stratify PONV risk based on: female sex, nonsmoking status, history of PONV/motion sickness, postoperative opioid use, and use of volatile anesthetics 1
• Patients with 1-2 risk factors should receive 2-drug prophylaxis 1
• Patients with ≥2-3 risk factors should receive 2-3 antiemetics (or 3-4 for highest risk) 1, 2

First-Line Prophylactic Agents

The most effective single drugs with high-certainty evidence for preventing vomiting are 3:

• 5-HT3 receptor antagonists: Ondansetron 8 mg IV (most studied), granisetron 1 mg IV, ramosetron, or palonosetron 0.25 mg IV 1, 3
• Corticosteroids: Dexamethasone 4-8 mg IV (single dose at induction shows similar efficacy to higher doses for most surgeries) 1, 3
• Dopamine (D2) antagonists: Droperidol (highly effective but use moderate doses due to side effect profile) 1, 3
• NK1 receptor antagonists: Aprepitant or fosaprepitant (most effective drug class, comparable to many drug combinations) 1, 3

Dosing Considerations

• Ondansetron: Recommended and high doses (8-24 mg oral, 8 mg IV) are more effective than low doses 3
• Dexamethasone: 4-5 mg shows similar efficacy to 8-10 mg for most surgeries; use 8 mg for major gastrointestinal surgery 1
• Granisetron: Recommended doses (1 mg IV, 2 mg oral) more effective than low doses 3
• Droperidol: Recommended and high doses more effective than low doses 3

Multimodal Combinations

Drug combinations are generally more effective than single agents for preventing vomiting. 1, 3 Effective two-drug combinations include 1:

• 5-HT3 antagonist + dexamethasone
• 5-HT3 antagonist + droperidol
• Dexamethasone + droperidol

For highest-risk patients, consider three-drug combinations: NK1 antagonist + 5-HT3 antagonist + dexamethasone 1

Baseline Risk Reduction

• Use total intravenous anesthesia (TIVA) with propofol rather than volatile anesthetics 1
• Implement multimodal analgesia to minimize opioid requirements 1
• Administer prophylactic IV acetaminophen to reduce pain and associated nausea 1
• Ensure adequate hydration and hemodynamic stability 1

Rescue Treatment

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

Rescue Agent Selection

• Ondansetron is the most effective drug for treating established PONV 4
• Amisulpride 10 mg IV (dopamine D2/D3 antagonist) shows significant benefit for rescue treatment after failed prophylaxis 5
• Olanzapine should be offered to patients who did not receive it prophylactically 1
• For patients already receiving olanzapine, consider: NK1 antagonist, benzodiazepines (lorazepam/alprazolam), dopamine antagonists, or cannabinoids (dronabinol/nabilone) 1

Second-Line Rescue Options

• Antihistamines: Promethazine (may cause sedation) 1
• Anticholinergics: Scopolamine (may cause dry mouth, blurred vision) 1
• Dopamine antagonists: Metoclopramide 20-30 mg (less effective than ondansetron but useful as add-on) 1

Re-evaluation

Before administering rescue therapy, reassess 1:

• Emetic risk of surgical procedure
• Disease status and concurrent illnesses
• Current medications
• Adequacy of initial prophylactic regimen

Safety Considerations

Serious Adverse Events

• Evidence for serious adverse events with most antiemetics is of very low to low certainty 3
• Droperidol may reduce serious adverse events (low certainty) 3
• Dexamethasone: Single perioperative doses do not increase wound infections, though long-term oncologic effects remain unknown 1

Common Side Effects

• Ondansetron: Probably increases headache but reduces sedation (moderate certainty) 3
• Droperidol: Probably reduces headache (moderate certainty) 3
• Dexamethasone: No effect on sedation (high certainty) 3
• Avoid sedating agents (anticholinergics, phenothiazines at higher doses) that may impair neurological examination 1

Special Populations

High-Dose Chemotherapy/Transplant

• Use three-drug combination: NK1 antagonist + 5-HT3 antagonist + dexamethasone 1
• Consider adding olanzapine as fourth agent (weak recommendation) 1

Cesarean Delivery

• Fluid preloading, vasopressors (ephedrine/phenylephrine), and lower limb compression reduce hypotension-related PONV 1
• Multimodal antiemetic approach with 5-HT3 antagonists, dopamine antagonists, and corticosteroids is effective 1
• Combination regimens (tropisetron 2 mg + metoclopramide 20 mg) are highly effective 1

Common Pitfalls

• Inadequate prophylaxis: Only 3.7-9.2% of patients receive guideline-recommended adequate prophylaxis despite its association with reduced PONV 6, 7
• Using same drug class for rescue: Always select a different antiemetic class for rescue treatment 1
• Underdosing: Low doses of ondansetron, granisetron, dexamethasone, and droperidol show no clinically important benefit 3
• Ignoring baseline risk reduction: Pharmacologic prophylaxis alone is insufficient without addressing modifiable risk factors 1