What Is Promethazine? Uses, Dosage, and What You Need to Know in 2026

Promethazine is one of those medications that has been quietly useful for decades. First developed in the 1940s, it remains a staple of emergency medicine, surgical care, and outpatient prescribing. Whether you've been prescribed it for the first time or you're trying to understand a medication a family member takes, this guide covers everything you need to know about promethazine in 2026.

What Is Promethazine?

Promethazine is a first-generation antihistamine and phenothiazine derivative. In plain terms, it's a prescription medication that blocks certain receptors in the brain and body to produce several therapeutic effects: reducing nausea, relieving allergy symptoms, preventing motion sickness, and causing sedation.

Promethazine was previously sold under the brand name Phenergan, which has since been discontinued. Today it is available only as a generic, though brand-name suppositories under the names Phenadoz and Promethegan are still on the market.

What Is Promethazine Used For?

Promethazine is FDA-approved for the following conditions:

• Allergic conditions: Seasonal and perennial allergic rhinitis (hay fever), allergic conjunctivitis, allergic skin reactions, hives (urticaria), and as an adjunct in anaphylaxis treatment
• Nausea and vomiting: Related to motion sickness, surgery, and postoperative recovery
• Motion sickness: Prevention and treatment of car, sea, and air sickness
• Sedation: Pre- and post-operative sedation, sedation during labor, and relief of anxiety before procedures

Off-label uses include nausea and vomiting during pregnancy (morning sickness and hyperemesis gravidarum), migraine-associated nausea, and as a mild sleep aid.

What Forms Does Promethazine Come In?

Promethazine is available in several forms, depending on clinical need:

• Oral tablets: 12.5 mg, 25 mg, and 50 mg — most common outpatient form
• Oral syrup: 6.25 mg per 5 mL — useful for children and patients who can't swallow tablets
• Rectal suppositories: 12.5 mg and 25 mg — ideal when vomiting prevents oral dosing
• Injectable: 25 mg/mL and 50 mg/mL — hospital and clinical settings only; currently in an active shortage

Promethazine Dosage: General Guidance

Always follow your doctor's specific instructions. These are general reference dosages:

• Allergies (adults): 25 mg at bedtime, or 12.5 mg before meals and at bedtime (range 6.25–12.5 mg three times daily)
• Motion sickness (adults): 25 mg 30-60 minutes before travel; then every 8-12 hours as needed
• Nausea and vomiting (adults): 25 mg orally or rectally; may repeat in 4-6 hours
• Preoperative sedation (adults): 25-50 mg the night before or 1-2 hours before the procedure
• Children (2 years and older): 0.5 mg/kg at bedtime; use lowest effective dose; NEVER for children under 2 years old

Is Promethazine a Controlled Substance?

No. Promethazine alone is not a DEA-scheduled controlled substance. It can be prescribed by any licensed prescriber, filled at any pharmacy, and is eligible for multiple refills. However, promethazine combined with codeine (a Schedule V substance in some states) does have controlled substance restrictions.

Key Safety Warnings

• NEVER give to children under 2 years old — can cause fatal respiratory depression
• Do not drive while taking promethazine until you know how it affects you
• Avoid alcohol — dramatically increases sedation and breathing risks
• Avoid with CNS depressants (opioids, sleep aids, benzodiazepines) — combined effect is greatly amplified
• Use with caution if you have COPD, sleep apnea, liver disease, or a seizure disorder

How Much Does Promethazine Cost?

Generic promethazine tablets are very affordable. A 30-count supply of 25 mg tablets typically costs $20-$30 at retail, and as little as $4.68 with a GoodRx coupon. Brand-name suppositories (Phenadoz, Promethegan) cost approximately $120 at retail but can be reduced to about $26 with discount coupons. Generic promethazine is covered as Tier 1 on most insurance plans.

Bottom Line

Promethazine is a versatile, widely available, and affordable generic medication with over 70 years of clinical use. If you're having trouble finding it, medfinder.com can locate it near you. For a deep dive into how the drug works, read our guide: How Does Promethazine Work? Mechanism of Action Explained.