Antiemetics for sedation patients are reached for either prophylactically in a patient with a history of nausea, or after the fact when nausea or vomiting develops during recovery. The four medications below all see use in that role; two — droperidol and promethazine — have their own full monograph on this site, linked below.
Droperidol
Is frequently used in the treatment of ambulatory patients. It can reduce nausea and vomiting by action on the CTZ.
Dose: 1.25–2.5 mg IV or IM, additional 1.25 mg doses to the desired effect (see the droperidol monograph for the FDA boxed warning on QT prolongation)
Onset: 3- 10 minutes
Peak Action: 30 minutes
Duration: 2-4 hours
Potential Adverse Reactions:
- Mild to moderate hypotension
- Drowsiness and prolonged recovery when given in larger doses.
Compazine (Prochorperazine)
Dose: 5 – 10 mg IV or deep IM
Administration Technique: Begin with lowest recommended dose. No more than 5 mg/minute IV. Maximum dose of 10 mg IV.
Potential Adverse Reactions: Drowsiness, dizziness
Phenergan (Promethazine)
Dose: 12.5 – 25 mg IV or 25-50 mg IM
Onset: 20 minutes
Peak Action: 4-6 hours
Duration: Up to 12 hours
Potential Adverse Reactions: Drowsiness, dry mouth.
Zofran (Ondansetron Hydrochloride)
Dose: 4 mg IV over 2-5 minutes
Onset: 20 minutes
Peak Action: 3.5 hours
Duration: Up to 8 hours
Potential Adverse Reactions: Minimal side effects
Choosing an Antiemetic
None of the four is a universal first choice; the pick depends on what else is on board and the patient’s own history. Droperidol carries an FDA boxed warning for QT prolongation, so a patient with a personal or family history of arrhythmia, or already on another QT-prolonging drug, argues for one of the others. Promethazine carries its own boxed warning for tissue injury on IV extravasation, so route and line placement matter as much as the dose. Ondansetron is the one on this list without a boxed warning, which is part of why it is often the default choice. Compazine sits between the two on sedative burden. As with any medication given during moderate sedation, the choice and the dose follow the facility’s sedation policy.
Educational reference for sedation providers, relocated from the previous version of this site — not a substitute for the current package insert, your facility protocols, or clinical judgment. Verify all doses against current references before clinical use.