Promethazine
PHENERGAN
What it isFirst-generation antihistamine with dopamine antagonism; nausea, vertigo and allergy.
Why this oneIt covers both histaminergic and dopaminergic nausea, which ondansetron does not.
What limits itSevere tissue injury including gangrene if it extravasates — the IV route is avoided. Contraindicated under age 2; strongly sedating and anticholinergic.
FDA-approved for
- nausea/allergy (~1951)
Off-label
- insomnia
- migraine
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Allergy | Adult | 25 mg QHS (or 12.5 mg before meals + QHS; or 6.25-12.5 mg TID) | lowest effective | per response |
| Motion sickness | Adult | 25 mg BID (first dose 0.5-1 h before travel) | ||
| Motion sickness | Pediatric (≥2 yr) | 12.5-25 mg BID | ||
| Nausea and vomiting | Adult | 25 mg, repeat q4-6h PRN | ||
| Nausea and vomiting | Pediatric (≥2 yr) | 0.5 mg/lb, adjusted to age/weight | ||
| Sedation | Adult | 12.5-25 mg QHS |
Renal Undefined
Hepatic Undefined
Nausea/vomiting doses may be repeated q4-6h PRN
Instructions
- Contraindicated under 2 years of age
- Use lowest effective dose; caution with concomitant respiratory depressants
- Do not use antiemetics for vomiting of unknown etiology in children/adolescents
Contraindications
- Children under 2 years of age
- Comatose states
- Hypersensitivity/idiosyncratic reaction to promethazine or other phenothiazines
- Treatment of lower respiratory tract symptoms including asthma
Cautions
- Respiratory depression, potentially fatal in young children
- Neuroleptic malignant syndrome
- Sedation; additive CNS/respiratory depression
- Extrapyramidal symptoms; lowers seizure threshold
- Paradoxical hyperexcitability
Adverse reactions
- Drowsiness, sedation, dizziness
- Blurred vision, dry mouth
- Extrapyramidal symptoms (oculogyric crisis, torticollis, tongue protrusion)
- Respiratory depression/apnea (potentially fatal)
- Leukopenia, thrombocytopenia, agranulocytosis
- Neuroleptic malignant syndrome
Pregnancy Use only if potential benefit justifies risk; given within 2 weeks of delivery may inhibit newborn platelet aggregation
Lactation Undefined
⚠ BOXED WARNINGS
- Respiratory depression in children under 2
- Severe tissue injury including gangrene
Cost, est. cash$10–$300/month
Generic entry1982
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.
Mechanism of action: Promethazine ballicule
Open Promethazine in the interactive console ↗
Memory aids: mascots and interaction avatars
hazing of Finnegan at prom
purple drank, a.k.a. Sizzurp, a concoction of promethazine/codeine syrup mixed with Sprite