What is Phenergan (promethazine) used for in adults with a history of nausea or vomiting?

What is Phenergan (Promethazine) Used For?

Phenergan (promethazine) is primarily used as an antiemetic for treating nausea and vomiting in adults, with additional FDA-approved indications for allergic conditions, motion sickness, and sedation, but should be administered with significant caution due to serious safety concerns. 1

Primary FDA-Approved Indications

Nausea and Vomiting

• The most common use is for active treatment of nausea and vomiting at 25 mg orally, rectally, or parenterally every 4-6 hours as needed. 1
• Promethazine works through central antidopaminergic mechanisms in the area postrema of the brain, blocking postsynaptic dopaminergic receptors. 2, 3
• The NCCN recommends promethazine specifically for opioid-induced nausea when prophylactic treatment is needed in patients with prior history. 2, 3
• For nonspecific nausea and vomiting in palliative care, promethazine serves as a dopamine receptor antagonist option alongside prochlorperazine, haloperidol, and metoclopramide. 2

Allergic Conditions

• For allergies, the average adult dose is 25 mg at bedtime, or 12.5 mg before meals and at bedtime if necessary. 1
• Single 25-mg doses will control minor transfusion reactions of an allergic nature. 1

Motion Sickness

• The average adult dose is 25 mg taken twice daily, with the initial dose taken 30-60 minutes before travel and repeated 8-12 hours later if necessary. 1
• On subsequent travel days, 25 mg should be given upon arising and before the evening meal. 1

Sedation and Procedural Use

• For nighttime sedation, adults require 25-50 mg at bedtime. 1
• The American Gastroenterological Association recommends promethazine 12.5-25 mg as an adjunct for sedation during minor surgical and endoscopic procedures. 3
• For preoperative medication, 50 mg the night before surgery relieves apprehension and produces quiet sleep. 1

Critical Administration and Safety Guidelines

Proper Dosing and Route

• Intravenous dosing is 12.5-25 mg, but must be infused slowly (≤25 mg/min) to minimize hypotension risk. 3
• Deep intramuscular injection is the preferred parenteral route due to serious risks with IV administration. 4, 5
• Clinical effects appear within 5 minutes of IV administration, with duration of action 4-6 hours and plasma half-life 9-16 hours. 3

Serious Safety Concerns Requiring Caution

• Injectable promethazine carries an FDA black box warning for risk of serious tissue injury, including thrombophlebitis, unintentional intra-arterial administration, perivascular extravasation, and tissue necrosis when administered incorrectly. 4, 6, 5
• Hypotension occurs frequently, particularly with rapid IV administration, requiring slow infusion rates. 3
• CNS depression and sedation occur frequently, which may be advantageous when sedation is desired but increases fall risk in older adults. 3, 7
• Extrapyramidal symptoms and neuroleptic malignant syndrome are serious potential complications. 3
• Respiratory depression can occur, especially when combined with other CNS depressants, and is contraindicated in children under 2 years of age. 3, 1

Special Considerations in Older Adults

• In elderly patients, start with 6.25 mg IV, which is as effective as higher doses but has significantly fewer adverse drug reactions (p=0.048). 7
• Anticholinergic effects (dry mouth, blurred vision, urinary retention) are particularly problematic in elderly patients. 3
• The combination of sedation, hypotension, and anticholinergic effects substantially increases fall risk in older adults already experiencing nausea or dizziness. 8

When NOT to Use Promethazine

Dizziness and Vertigo

• The American Academy of Otolaryngology-Head and Neck Surgery explicitly recommends AGAINST routine use of promethazine for treating dizziness or benign paroxysmal positional vertigo (BPPV). 8
• Vestibular suppressants like promethazine interfere with central compensation in peripheral vestibular conditions, potentially prolonging recovery and delaying natural adaptation. 8
• No evidence exists that promethazine is effective as definitive primary treatment for BPPV or as a substitute for repositioning maneuvers. 8
• Promethazine may only be used for short-term management of severe nausea and vomiting in acutely symptomatic dizzy patients who cannot tolerate other treatments. 8

Comparative Effectiveness and Alternative Agents

When Promethazine May Be Preferred

• Promethazine may be suitable when sedation is desirable as an additional therapeutic effect. 9
• It can be used as a second-line agent when ondansetron or other 5-HT3 antagonists fail to control symptoms. 3
• For opioid-induced pruritus, promethazine may be beneficial as an antihistamine option. 3

When Alternative Agents Are Superior

• Ondansetron is as effective as promethazine for nausea and vomiting but is not associated with sedation, akathisia, or tissue injury risks, making it a preferred first-line agent in most emergency department settings. 9, 6
• For gastroparesis-related nausea, metoclopramide has the strongest evidence among antiemetics. 2
• Droperidol is more effective than promethazine but carries an FDA black box warning for QT prolongation, limiting its use to refractory cases. 9

Common Pitfalls to Avoid

• Never use promethazine as primary treatment for dizziness or vertigo—this delays effective treatment, exposes patients to unnecessary adverse effects, and interferes with natural vestibular compensation. 8
• Never administer IV promethazine rapidly or through small peripheral veins—use large, patent veins, dilute the medication, and infuse slowly to prevent thrombophlebitis and tissue necrosis. 4, 5
• Do not use promethazine in children under 2 years of age due to fatal respiratory depression risk. 3, 1
• Avoid promethazine when sedation is undesirable or when patients are at high risk for falls. 9, 7
• Do not use in vomiting of unknown etiology in children and adolescents without first establishing the cause. 1