What anti-emetic (anti-vomiting medication) does not prolong the QT interval?

Antiemetics Without QT Prolongation Risk

Prochlorperazine is the preferred antiemetic that does not significantly prolong the QT interval and can be safely used in patients at risk for cardiac arrhythmias. 1

First-Line Safe Options

Prochlorperazine (5-10 mg QID) is recommended as a safe antiemetic without significant QT prolongation effects, functioning as an effective dopamine receptor antagonist for nausea and vomiting. 2, 1 However, monitor patients for extrapyramidal symptoms (dystonic reactions), which can be managed with diphenhydramine if they occur. 2, 1

Alternative Safe Antiemetics

• Promethazine offers antiemetic effects through antihistamine properties without significant QT prolongation, though it causes sedation and anticholinergic effects. 1, 3

• Diphenhydramine (12.5-25 mg TID) provides antiemetic properties without QT prolongation concerns, but expect sedation and anticholinergic effects. 2, 1

• Meclizine (12.5-25 mg TID) is another antihistamine option without QT risk. 2

• Scopolamine patch (1.5 mg every 3 days) works as a muscarinic antagonist without QT prolongation risk. 2

• Aprepitant (80 mg/day), an NK1 receptor antagonist, does not prolong QT and is highly effective, particularly for chemotherapy-induced nausea. 2

Antiemetics to Avoid

Do not use these agents if QT prolongation is a concern:

• Ondansetron and other 5-HT3 antagonists (except palonosetron) carry FDA warnings for QT prolongation, particularly at higher doses. 2, 4, 5

• Droperidol has a black box warning for QT prolongation and is contraindicated in at-risk patients. 1, 3

• Domperidone carries significant QT prolongation risk and should be avoided. 1

• Metoclopramide can prolong QT interval, though this risk is dose-dependent. 4

Clinical Algorithm

1. For general nausea/vomiting: Start with prochlorperazine 5-10 mg QID. 2, 1

2. If sedation is acceptable or desired: Use promethazine or diphenhydramine. 1, 3

3. For chemotherapy-induced nausea: Consider aprepitant combined with dexamethasone (which does not prolong QT). 2

4. If extrapyramidal symptoms occur: Administer diphenhydramine 25-50 mg or benztropine (if diphenhydramine allergy exists). 2

Important Caveats

Risk factors that increase susceptibility to QT prolongation include: female gender, electrolyte abnormalities (especially hypokalemia and hypomagnesemia), bradycardia, recent conversion from atrial fibrillation, congestive heart failure, and concomitant use of multiple QT-prolonging drugs. 2, 6

Before initiating any antiemetic in at-risk patients: Correct electrolyte abnormalities, particularly potassium and magnesium levels, to minimize QT prolongation risk. 6, 1

For breakthrough nausea: Consider adding benzodiazepines like lorazepam (0.5-2.0 mg every 4-6 hours), which do not affect QT interval, or dexamethasone for short-term use. 2, 1

Palonosetron is the exception among 5-HT3 antagonists - regulatory authorities have not issued QT warnings for this agent specifically, unlike other drugs in its class. 2 However, given the class effect concerns, prochlorperazine remains the safer first-line choice when QT prolongation is a primary concern.