Dexamethasone, Ondansetron and Droperidol

Mechanism

Synergistic Mechanism of Combined Prophylaxis

The combined use of two or more antiemetics with different molecular targets of action offers a synergistic therapeutic effect superior to increasing the dose of a single compound:

• Ondansetron: Selective antagonist of the serotonin 5-HT₃ receptor, blocking gastric afferent vagal transmission to the bulbar postrema area.
• Dexamethasone: High-potency corticosteroid that exerts a powerful central preventive effect at the cellular level, reducing the synthesis of inflammatory prostaglandins and attenuating systemic inflammation that stimulates the vomiting center.
• Droperidol: Butyrophenone that acts as a potent and selective antagonist of central dopamine type D₂ receptors located in the gastric chemoreceptor trigger zone.

Indicators and dose

Optimal Dosage and Administration Times

Security

Risk factors and Apfel Scale

Prophylactic clinical decision-making is governed by the simplified Apfel predictive scale, which associates a cumulative value with four independent clinical risk factors:

1. Female sex.
2. Personal history of PONV or severe motion sickness (traveler's motion sickness).
3. Active non-smoking status.
4. Postoperative use of systemic opioid analgesics.

The presence of 1, 2, 3 or 4 of these factors predicts a risk of suffering PONV of 20%, 40%, 60% and 80%, respectively, requiring the mandatory establishment of preventive multimodal pharmacological prophylactic guidelines.

Class Contraindications

• Ondansetron and Droperidol: Congenital long QT syndrome or pre-existing acquired prolongation of the QTc interval. Both compounds can alter myocardial repolarization by dose-dependently blocking hERG rectifying potassium channels, requiring prior electrocardiographic control if basal arrhythmias are suspected.
• Dexamethasone: Patients with severe, metabolically uncontrolled diabetes mellitus (it can induce acute peaks of refractory perioperative hyperglycemia that are difficult to control and impair healing).