Ondansetron

ZOFRAN

What it is5-HT3 receptor antagonist; nausea and vomiting.

Why this oneBroad oral, dissolving-tablet and IV availability makes it the default 5-HT3 antiemetic without sedation or motor effects.

What limits itConstipation and QT prolongation are the practical limits; avoid stacking QT-prolonging drugs. It does not treat vestibular nausea.

FDA-approved for

FDA dosing	Population	Start	Target	Max
CINV — highly emetogenic chemotherapy	Adults	24 mg once (three 8 mg tablets)	24 mg 30 min pre-chemo	24 mg/dose
CINV — moderately emetogenic chemotherapy	Adults & children ≥12 yr	8 mg BID	8 mg BID	8 mg BID
CINV — moderately emetogenic chemotherapy	Children 4-11 yr	4 mg TID	4 mg TID	4 mg TID
Radiotherapy-induced N/V	Adults	8 mg TID	8 mg TID	8 mg TID
Postoperative N/V	Adults	16 mg once (two 8 mg tablets) 1 h before anesthesia	16 mg once	16 mg/dose

Renal No adjustment needed

Hepatic Severe (Child-Pugh ≥10): do not exceed 8 mg total daily dose

Give first dose 30 minutes before start of chemotherapy (1-2 h before each radiotherapy fraction)

Concomitant use of apomorphine (profound hypotension and loss of consciousness reported)

Pregnancy Pregnancy Category B; animal studies show no fetal harm; use only if clearly needed

Lactation Undefined

NO BOXED WARNINGS

Principal riskQT prolongation

Cost, est. cash$20–$1,500/dose or month

Generic entry2006

Therapeutic safety burden2 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades3 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryB

Defining liabilitySedation, QT prolongation, extrapyramidal symptoms or anticholinergic toxicity vary by receptor target.

Box: minimal PK interactions