Promethazine

Pronunciation: proh-METH-a-zeen.

Generic name
promethazine hydrochloride
Drug class
First-generation antihistamine; phenothiazine derivative
Form
Tablet, oral solution/elixir, injection, suppository (availability varies by country)
Route
Oral, intramuscular injection, rectal (suppository, in some markets)
Legal status
Prescription-only in most contexts; some oral forms are pharmacist-supervised over-the-counter in Australia (S3) and available without a prescription in some other markets -- check your local product.

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Phenergan (6), Approximately 50 other generic oral promethazine brands (6) · Full directory

What promethazine hydrochloride is and how it works

Promethazine is an older-generation antihistamine used to relieve allergic symptoms, prevent and treat nausea and vomiting (including motion sickness), and provide short-term sedation before or after a procedure. (1) (6) (2)

Promethazine has two genuine, serious safety warnings that are especially important for children and for anyone receiving the injectable form. It must not be used in very young children because of a real risk of fatal slowed or stopped breathing, and regulators in several countries have more recently restricted its use in children up to 6 years old because of a risk of serious behavioural and psychiatric effects. The injectable form also carries a real risk of severe tissue damage, including gangrene, if it leaks outside the vein or is given incorrectly -- it should only ever be given by a trained healthcare professional using the correct technique.

Mechanism of action: how promethazine hydrochloride works

Promethazine is a phenothiazine derivative with potent H1-antihistamine, anticholinergic, and antidopaminergic activity, producing antiallergic, antiemetic, and sedative effects; its dopamine-receptor-blocking activity underlies the rare risk of extrapyramidal symptoms and Neuroleptic Malignant Syndrome. (1)

What promethazine hydrochloride is used for

Allergic conditions

Used to relieve symptoms of allergic rhinitis, allergic conjunctivitis, hives (urticaria), and angioedema, and as adjunctive treatment during anaphylactic reactions alongside other emergency treatment. (1) (3)

Nausea, vomiting, and motion sickness

Used to prevent and treat nausea and vomiting, including motion sickness, and for sedation before or after surgery. (1)

Short-term sedation / insomnia (adults)

Used in some markets for short-term treatment of insomnia in adults and for short-term sedation in children (subject to the pediatric age restrictions described in this page). (3)

Before taking promethazine hydrochloride

Do not take / not appropriate for

  • Do not give promethazine to a child younger than 2 years of age -- there is a real risk of fatal slowed or stopped breathing. (all countries) (1)
  • Do not give oral promethazine to a child younger than 6 years of age. (United Kingdom, Australia, New Zealand (and likely Ireland/EU -- confirm with your local product label)) (3) (6) (7)
  • Do not take promethazine if you are in a coma or have severe CNS depression, or if you have a known allergy to promethazine or other phenothiazine medicines. (all countries) (1) (3)
  • Do not take promethazine if you have taken a monoamine oxidase inhibitor (MAOI) medicine within the last 14 days. (United Kingdom) (3)
  • The injectable form must never be given just under the skin (subcutaneously) -- this is specifically contraindicated because of the tissue-injury risk. (all countries (injectable form)) (2)
  • Do not use promethazine in children for lower respiratory tract symptoms, including asthma -- it is specifically contraindicated for this use. (United States) (1)

Tell your clinician about

  • The exact age of any child being considered for this medicine.
  • Any history of seizures, sleep apnoea, or breathing problems.
  • Any other sedating medicines, opioids, or alcohol use.
  • Any history of liver disease, heart rhythm problems (including a prolonged QT interval), or bone marrow problems.
  • Whether you are pregnant, planning pregnancy, or breastfeeding.
(1) (3) (4)

How to take promethazine hydrochloride

  • Take exactly as directed by your clinician or the product label; do not use for longer than advised.
  • If the injectable form is prescribed, it will be given by a healthcare professional -- preferably as a deep injection into a muscle, never just under the skin.
  • Avoid driving or operating machinery until you know how promethazine affects you, since it commonly causes drowsiness.
  • Avoid alcohol and other sedating medicines while taking promethazine, since these effects can add up.
(1) (3)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6) (7)

Missed dose

If promethazine is being used regularly and a dose is missed, contact your prescriber or pharmacist for guidance rather than doubling the next dose.

Overdose

Seek emergency medical help immediately for a suspected overdose. Symptoms can include severe drowsiness, slowed or stopped breathing, confusion, uncontrolled movements, seizures, or a fast or irregular heartbeat, and can be fatal, especially in children. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Drowsiness and sedation.

What to notice: Drowsiness and sedation.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Dry mouth, blurred vision, and constipation (anticholinergic-type effects).

What to notice: Dry mouth, blurred vision, and constipation (anticholinergic-type effects).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (3)

Dizziness.

What to notice: Dizziness.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Signs of dangerously slowed or stopped breathing in a child — boxed_warning

Symptoms: Slow, shallow, or noisy breathing, long pauses between breaths, blue-tinged lips or skin, or unusual drowsiness/difficulty waking in a child who has taken promethazine.

Action: Seek emergency medical help immediately. This is why promethazine must not be given to children younger than 2 (and, in the UK, Australia, and New Zealand, younger than 6) years of age. (1)

New behavioural or psychiatric changes in a young child — regulator_confirmed_serious_warning

Symptoms: Unusual hyperactivity, aggression, or hallucinations (seeing or hearing things that are not there) in a child aged 2 to 5 years.

Action: Contact a clinician promptly. This is the basis for the UK, Australian, and New Zealand restriction of oral promethazine to children 6 years and older. (6) (7)

Signs of severe tissue injury at an injection site — boxed_warning

Symptoms: Persistent or worsening pain, burning, swelling, redness, or loss of sensation at or near an injection site, or any skin colour change or blistering.

Action: Report this immediately to the healthcare team -- this can indicate the severe tissue damage (including gangrene) described in the boxed warning for the injectable form, which has sometimes required surgery, skin grafting, or amputation. (2)

Signs of Neuroleptic Malignant Syndrome (NMS) or severe extrapyramidal reactions — emergency

Symptoms: High fever, severe muscle stiffness, confusion, irregular heartbeat or blood pressure, or uncontrolled muscle movements.

Action: Seek emergency medical help immediately -- this is a rare but potentially fatal reaction associated with promethazine and related medicines. (1)

Signs of a serious allergic reaction — emergency

Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives.

Action: Seek emergency medical help immediately. (3)

Interactions

  • Other sedating or respiratory-depressant medicines (opioids, benzodiazepines, other sedatives) and alcohol can add to promethazine's sedative and breathing-suppressant effects, and this combination is specifically flagged as risky in children. (1)
  • Monoamine oxidase inhibitors (MAOIs) taken within the previous 14 days are contraindicated with promethazine. (3)
  • Medicines that can prolong the QT interval may increase the risk of serious heart rhythm problems when combined with promethazine. (4)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Discuss with your clinician; promethazine has been used in pregnancy for nausea, but any use should be individually assessed by a prescriber. (1) (2) (3) (4) (5) (6) (7)

Children

Contraindicated under 2 years of age in all markets reviewed (fatal respiratory depression risk); contraindicated under 6 years of age specifically in the UK, Australia, and New Zealand (adding a psychiatric/CNS risk in ages 2-5); Canada's current position on the under-6 restriction could not be confirmed and is not assumed either way. (1) (2) (3) (4) (5) (6) (7)

Elderly

Older adults may be more sensitive to sedation, confusion, dizziness, and anticholinergic effects (such as urinary retention or constipation); dose with caution. (1) (2) (3) (4) (5) (6) (7)

Hepatic_impairment

Not specifically quantified in the sources reviewed for this dossier; use with caution and clinician guidance. (1) (2) (3) (4) (5) (6) (7)

Renal_impairment

Not specifically quantified in the sources reviewed for this dossier; use with caution and clinician guidance. (1) (2) (3) (4) (5) (6) (7)

Source_ids

US-DAILYMED-PHENERGAN-TABLET-2026,UK-EMC-PHENERGAN-TABLET-2026,AU-TGA-PHENERGAN-SAFETY-UPDATE-2024,NZ-MEDSAFE-PROMETHAZINE-SAFETY-ALERT-2024 (1) (2) (3) (4) (5) (6) (7)

Monitoring

Before starting

  • Confirm the patient's exact age before any pediatric use
  • Review for other sedating/respiratory-depressant medicines
  • Review for MAOI use in the past 14 days

During treatment

  • Watch for breathing changes, unusual drowsiness, or behavioural/psychiatric changes in children.
  • For the injectable form: monitor the injection site closely for pain, burning, swelling, or colour change during and after administration.
(1) (2)

Storage

Store at room temperature, protected from light, out of reach of children.

Study the drug class: Antihistamines

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing information (tablet and injection), the UK EMC SmPC, and Australian/New Zealand regulator safety updates reviewed for this dossier; verify against the current full label before prescribing.

United States

Indication: Allergic conditions, nausea/vomiting, sedation

Dose summary: Individualised by indication and age; contraindicated under 2 years; caution and lowest effective dose in children 2 years and older; avoid concomitant respiratory depressants in pediatric patients.

Renal context: Not specifically addressed in the sources reviewed. (1)

United Kingdom / Australia / New Zealand

Indication: Allergic conditions, antiemetic use, short-term sedation/insomnia

Dose summary: Individualised by indication and age; contraindicated under 6 years (updated 2024) for the combined respiratory-depression and psychiatric/CNS risk.

Renal context: Not specifically addressed in the sources reviewed. (3) (6) (7)

Mechanism of action

Hepatic guidance

Not specifically quantified in the sources reviewed for this dossier.

Overdose note

No specific antidote; manage with supportive care and close respiratory and cardiac monitoring, particularly in children. (1)

Frequently asked questions

Why can't young children take promethazine?

Because of a real, FDA boxed-warning-level risk of fatal slowed or stopped breathing in children younger than 2 years of age. More recently (2024), the UK, Australia, and New Zealand extended this restriction to children younger than 6, after finding a separate risk of serious psychiatric and behavioural effects (hyperactivity, aggression, hallucinations) in children aged 2 to 5. (1) (6) (7)

Why is the injectable form given so carefully?

Because promethazine injection carries a genuine boxed warning for severe tissue injury, including gangrene, if it leaks outside the vein, is injected into an artery by mistake, or is given just under the skin. It should only be given by a trained healthcare professional, preferably as a deep injection into a muscle. (2)

Is the age restriction the same in every country?

No -- this is a genuine difference between regulators. As of this review, the current US label still restricts use to children 2 years and older, while the UK, Australia, and New Zealand restrict oral promethazine to children 6 years and older. Always follow the product label and your clinician's guidance for your own country. (1) (3) (6)

What is the mechanism of action of promethazine hydrochloride?

Promethazine is a phenothiazine derivative with potent H1-antihistamine, anticholinergic, and antidopaminergic activity, producing antiallergic, antiemetic, and sedative effects; its dopamine-receptor-blocking activity underlies the rare risk of extrapyramidal symptoms and Neuroleptic Malignant Syndrome. (1)

What is the generic name of Promethazine?

The generic name is promethazine hydrochloride. (1) (3)

What class of drug is promethazine hydrochloride?

Promethazine is classed as: First-generation antihistamine; phenothiazine derivative. (1) (3)

References

  1. PHENERGAN (promethazine hydrochloride) tablets, USP -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information · United States · accessed 2026-07-30 · source 1
  2. PROMETHAZINE HYDROCHLORIDE injection, solution -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information · United States · accessed 2026-07-30 · source 2
  3. Phenergan 25 mg tablets -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Sanofi · United Kingdom · accessed 2026-07-30 · source 3
  4. Phenergan tablets/elixir -- HPRA product licence and 2024 safety reviewHealth Products Regulatory Authority (HPRA), Ireland · Ireland (European Union) · accessed 2026-07-30 · source 4
  5. Promethazine Hydrochloride Injection USP -- Product MonographHealth Canada -- Sandoz Canada Inc. product monograph · Canada · accessed 2026-07-30 · source 5
  6. Promethazine hydrochloride (Phenergan) not to be used in children under 6 -- TGA safety updateTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 6
  7. Promethazine (oral): Do not use in children under 6 years of age -- Medsafe safety alertMedsafe (New Zealand regulator) · New Zealand · accessed 2026-07-30 · source 7

Brand names by country

Single-ingredient promethazine hydrochloride names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Phenergan50 mg/mL, 25 mg/mL, 12.5 mg · hikma pharmaceuticals usa inc.
  • PROMETHEGAN50 mg, 12.5 mg, 25 mg · cosette pharmaceuticals, inc.
  • PROMETHAZINE HCI50 mg/mL, 25 mg/mL · hf acquisition co. llc, dba healthfirst

United Kingdom

  • Phenergan (3)MHRA licensed emc smpc confirmed · 10 mg/5 mL elixir, 25 mg tablet · Sanofi

Canada

  • HISTANTIL
  • PMS-PROMETHAZINE SYR

Australia

  • Phenergan (6)TGA approved S3 pharmacist only confirmed · 10 mg/5 mL elixir, 25 mg tablet · Sanofi Australia
  • Approximately 50 other generic oral promethazine brands (6)TGA approved confirmed · varies by brand · Multiple sponsors

New Zealand

  • Phenergan Tablets / Phenergan Elixir (7)Medsafe registered confirmed · not specified in source · Sanofi
  • Allersoothe (7)Medsafe registered confirmed · 10 mg, 25 mg (tablet) · not specified in source
View brands in additional countries.

European Union

Phenergan (Ireland) (4), Atosil (Germany, brand name identified but not independently verified this dossier) (4)

This page provides general reference information about promethazine and is not a substitute for advice from the prescriber managing your treatment. Pediatric age restrictions genuinely differ between countries -- always follow the product label and your clinician's guidance for where you live.

Related medicines

Related conditions