What are the best antiemetics for pre-operative prophylaxis?

Best Antiemetics for Pre-Operative Prophylaxis

A multimodal approach using first-line antiemetics should be implemented for pre-operative nausea and vomiting prophylaxis, with the combination of a serotonin (5HT3) antagonist (e.g., ondansetron), a corticosteroid (e.g., dexamethasone), and a dopamine (D2) antagonist (e.g., droperidol) being most effective for patients with multiple risk factors. 1

Risk Assessment and Stratification

Before selecting antiemetics, assess the patient's PONV risk using validated tools:

• Apfel Score - most commonly used, considers:

  • Female gender
  • Non-smoking status
  • History of PONV or motion sickness
  • Expected postoperative opioid use

• Risk-based prophylaxis approach:

  • 0-1 risk factors: Consider single antiemetic
  • 1-2 risk factors: Two-drug combination
  • ≥2 risk factors: Three-drug combination 1

First-Line Antiemetics

1. Serotonin (5HT3) Antagonists:

   • Ondansetron: 4 mg IV (most studied) 1, 2
   • Provides ~25% relative risk reduction when used alone 1
   • FDA-approved for prevention of postoperative nausea and vomiting 2

2. Corticosteroids:

   • Dexamethasone: 4-8 mg IV 1
   • The DREAMS Trial (1350 patients) showed 8 mg reduced PONV at 24h and need for rescue antiemetics up to 72h 1
   • 4-5 mg dose has similar clinical effects to 8-10 mg dose 1

3. Dopamine (D2) Antagonists:

   • Droperidol: Low dose (0.625-1.25 mg) 1
   • Similar efficacy to 5HT3 antagonists 3

Second-Line Antiemetics

1. Antihistamines:

   • Promethazine: 6.25-25 mg 1, 4
   • Particularly effective as rescue therapy after ondansetron or droperidol prophylaxis failure 4

2. Anticholinergics:

   • Scopolamine: Transdermal patch 1
   • Effective for postoperative nausea and vomiting 1

3. Other D2 Antagonists:

   • Metoclopramide: 10 mg 1
   • Limited by side effects including sedation and extrapyramidal symptoms 3

Additional Options for High-Risk Patients

1. Neurokinin-1 (NK1) Receptor Antagonists:

   • Aprepitant: For high-risk patients 1
   • Not superior to ondansetron in PONV prevention 1

2. Gabapentinoids:

   • Gabapentin/Pregabalin: Preoperative administration can reduce PONV 1
   • Caution: increased risk of visual disturbance (pregabalin) and sedation (both) 1

3. Anxiolytics for Anxiety-Associated Nausea:

   • Lorazepam: 0.5-2 mg orally, IV, or sublingually 5
   • Particularly useful when anxiety is contributing to nausea 5

Multimodal Approach

For optimal results, combine:

1. Pharmacological strategies:

   • Multiple antiemetics acting at different receptor sites 1
   • Prophylactic analgesia (IV acetaminophen) can reduce nausea incidence 1

2. Anesthetic technique modifications:

   • Total intravenous anesthesia (TIVA) with propofol instead of volatile anesthetics 1
   • Minimize opioid use through multimodal analgesia 1
   • Adequate hydration 3

Rescue Therapy

If breakthrough PONV occurs despite prophylaxis:

• Use an antiemetic from a different class than what was used for prophylaxis 1, 4
• Promethazine (6.25-25 mg) has shown superior efficacy as rescue after ondansetron or droperidol prophylaxis failure 4

Common Pitfalls and Caveats

1. Avoid using the same drug class for rescue that was used for prophylaxis - significantly lower efficacy 1, 4

2. Consider side effect profiles:

   • Dexamethasone: Potential immunosuppressive effects on long-term oncological outcomes remain unknown 1
   • Second-line agents: Higher incidence of sedation, dry mouth, blurred vision, and dyskinesia 1
   • Gabapentinoids: Visual disturbances and sedation 1

3. Special populations:

   • Elderly: Use lower doses of benzodiazepines 5
   • Patients with electrolyte abnormalities or cardiac conditions: Monitor ECG with certain antiemetics 5

The evidence strongly supports that a multimodal approach to PONV prophylaxis should be incorporated into perioperative care protocols, with antiemetic selection based on patient risk factors and the specific surgical context 1.