Promethazine Hydrochloride Dosage UK | Cured Pharmacy

Clinically Proven UK Registered Pharmacy

Emergency Promethazine Hydrochloride Quick Reference

UK-registered clinical team
Confidential and secure
No GP visit needed
Fast and discreet delivery
Genuine Products
UK-licensed only
Fast Delivery
Next-day available
Expert Advice
UK pharmacists
Woman using Cured Pharmacy online consultation for treatment
From £17.54 Starting dose — clinically approved
LIVE PRICING

Our Pricing

Pricing Disclaimer: Prices on some pages may not be up to date — the live pricing table below and pricing shown during consultation are official current prices and take precedence over any other figures on the site.

Phenergan 25mg Tablets x56 - UK-licensed prescription Treatment
Treatment

Phenergan 25mg Tablets x56

From £17.54

Future orders save 5%
Buy Now
Phenergan Elixir - UK-licensed prescription Treatment
Treatment

Phenergan Elixir

From £15.49

Future orders save 5%
Buy Now
Phenergan Night Tablets 25mg - UK-licensed prescription Treatment
Treatment

Phenergan Night Tablets 25mg

From £8.39

Future orders save 5%
Buy Now

Emergency Promethazine Hydrochloride Quick Reference

Published on: June 03, 2026

When you need reliable promethazine hydrochloride dosage UK information quickly, this emergency reference guide provides essential safety data for adults and children. Promethazine (brand name Phenergan) is a first-generation antihistamine licensed in the UK for allergic reactions, motion sickness, and short-term insomnia, available from Cured Pharmacy with transparent pricing and expert clinical support.

Standard Promethazine Hydrochloride Dosage UK Guidelines

For adults and children over 10 years, the standard oral dose for allergic conditions is 25mg at night, or 10-20mg two to three times daily [1]. In emergency situations involving severe allergic reactions without anaphylaxis, a single 25mg dose may provide rapid symptom relief within 20 minutes, though effects typically peak at 2-3 hours [2].

Children aged 5-10 years require reduced dosing: 10-25mg daily in divided doses for allergies, with a maximum single dose of 25mg [1]. For motion sickness prevention, adults should take 25mg the night before travel, followed by 25mg on waking, with further 25mg doses every 8 hours if needed during the journey [3].

Promethazine elixir (5mg/5ml) offers flexible dosing for children and adults who cannot swallow tablets. The liquid formulation allows precise dose adjustment based on age and body weight, particularly important in paediatric use where overdosing carries significant risks [2].

Maximum Safe Doses

Adults should not exceed 100mg promethazine in any 24-hour period [1]. Higher doses increase the risk of anticholinergic side effects including urinary retention, confusion, and paradoxical agitation. Elderly patients often require dose reduction due to increased sensitivity to sedative and anticholinergic effects, with many UK prescribers recommending a maximum of 50mg daily in those over 65 years [3].

When to Use Promethazine in Emergency Situations

Promethazine is appropriate for moderate allergic reactions presenting with urticaria, rhinitis, or conjunctivitis without respiratory compromise [2]. It blocks histamine H1 receptors, reducing itch, swelling, and mucus secretion within 20-60 minutes of oral administration.

This medication is NOT suitable for anaphylaxis or severe allergic reactions involving breathing difficulty, lip or tongue swelling, or circulatory collapse. These situations require immediate 999 emergency services and intramuscular adrenaline [4]. Promethazine may be given after adrenaline in hospital settings but should never replace it as first-line treatment.

For acute motion sickness that develops during travel, promethazine offers limited benefit due to delayed onset. Prevention requires dosing before symptoms begin, ideally 12-24 hours before departure [3].

Promethazine Side Effects UK Patients Should Monitor

Sedation is the most common side effect, affecting approximately 50% of users at standard doses [1]. This drowsiness can persist for 12-24 hours, making promethazine unsuitable before driving, operating machinery, or performing tasks requiring alertness. The MHRA specifically warns against next-day driving after evening doses.

Anticholinergic effects include dry mouth (30-40% of users), blurred vision, constipation, and urinary hesitancy [2]. Elderly patients and those with pre-existing prostatic hypertrophy face higher risks of urinary retention requiring catheterisation. Glaucoma patients should avoid promethazine entirely as it can precipitate acute angle-closure attacks.

Paradoxical excitation occurs in approximately 5-10% of children, manifesting as hyperactivity, nightmares, or agitation rather than sedation [3]. If this develops, discontinue promethazine immediately and consult your prescriber for alternative antihistamine options.

Serious Adverse Effects Requiring Medical Attention

Seek immediate medical help if you experience involuntary muscle movements, severe dizziness, yellowing of skin or eyes, or signs of blood disorders such as unexplained bruising or persistent sore throat [4]. Though rare, promethazine can cause neuroleptic malignant syndrome, characterised by high fever, muscle rigidity, and altered consciousness — a medical emergency requiring hospital treatment.

Product Strength Pack Size Starting Price
Phenergan 25mg Tablets 25mg 56 tablets From £17.54
Phenergan Elixir 5mg/5ml 100ml bottle From £15.49
Phenergan Night Tablets 25mg 14 tablets From £8.39

Phenergan Tablets vs Phenergan Elixir: Choosing the Right Formulation

Phenergan 25mg tablets from Cured Pharmacy (from £17.54 for 56 tablets) provide convenient dosing for adults and children over 10 years who can swallow tablets reliably. The tablet formulation offers longer shelf life and portability for travel or emergency kits.

Phenergan Elixir (5mg/5ml) suits children aged 5-10 years and adults requiring flexible dosing below 25mg. The liquid formulation allows precise measurement using the supplied oral syringe, essential for weight-based paediatric dosing. Elixir typically costs slightly less per dose for lower-strength requirements.

Phenergan Night Tablets contain the same 25mg promethazine hydrochloride but are specifically licensed and packaged for short-term insomnia treatment. The formulation is identical to standard Phenergan tablets — the distinction lies in licensed indication and pack size rather than pharmacological difference.

Drug Interactions and Contraindications with Promethazine

Promethazine significantly enhances the sedative effects of alcohol, benzodiazepines, opioids, and other central nervous system depressants [1]. Combining these substances increases risks of respiratory depression, profound sedation, and falls, particularly in elderly patients. Always inform your UK prescriber of all medications you take, including over-the-counter products.

Monoamine oxidase inhibitors (MAOIs) interact dangerously with promethazine, potentially causing severe hypotension and central nervous system toxicity [2]. Allow at least 14 days after stopping MAOIs before starting promethazine. Tricyclic antidepressants amplify anticholinergic side effects, increasing risks of confusion, urinary retention, and cardiac arrhythmias.

Absolute contraindications include children under 2 years (risk of fatal respiratory depression), comatose states, and known hypersensitivity to phenothiazines [4]. Relative contraindications requiring specialist assessment include severe liver disease, epilepsy, Reye's syndrome, and bone marrow depression.

Pregnancy and Breastfeeding Considerations

The MHRA advises avoiding promethazine during pregnancy unless potential benefits outweigh risks, particularly in the first trimester [4]. Limited human data suggest possible associations with cardiac malformations when used near conception, though causality remains unproven. Promethazine passes into breast milk and may cause sedation or irritability in nursing infants — breastfeeding mothers should discuss safer antihistamine alternatives with their UK prescriber.

How to Buy Promethazine Online UK Safely Through Cured Pharmacy

All promethazine products at Cured Pharmacy require completion of a free online clinical assessment reviewed by UK-registered prescribers. This typically takes under 3 minutes and ensures promethazine is appropriate for your specific symptoms, medical history, and current medications. Our superintendent pharmacist Tarun Kumar (GPhC 2233073) oversees all clinical decisions to maintain the highest safety standards.

Once approved, your prescription is dispensed from our UK-registered pharmacy (GPhC 9012511) using only genuine MHRA-licensed medicines. We offer discreet packaging and competitive pricing — Phenergan 25mg tablets start from £17.54, with transparent costs shown before you begin the consultation process.

If promethazine is unsuitable for your circumstances, our prescribers will recommend alternative treatments such as non-sedating antihistamines (cetirizine, loratadine) or different approaches to motion sickness management. Your safety always takes precedence over completing a sale — a principle central to responsible online pharmacy practice in the UK.

Scientific References

  1. Joint Formulary Committee. (2024). British National Formulary (BNF) 87. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk/drugs/promethazine-hydrochloride/ [accessed 13 August 2026]
  2. Simons, F. E. R., & Simons, K. J. (2011). Histamine and H1-antihistamines: Celebrating a century of progress. Journal of Allergy and Clinical Immunology, 128(6), 1139-1150. https://doi.org/10.1016/j.jaci.2011.09.005 [accessed 13 August 2026]
  3. Spinks, A., & Wasiak, J. (2011). Scopolamine (hyoscine) for preventing and treating motion sickness. Cochrane Database of Systematic Reviews, (6), CD002851. https://doi.org/10.1002/14651858.CD002851.pub4 [accessed 13 August 2026]
  4. Medicines and Healthcare products Regulatory Agency. (2023). Promethazine hydrochloride: Updated advice on use in children. Drug Safety Update, 16(8), A1. https://www.gov.uk/drug-safety-update/promethazine-hydrochloride-updated-advice-on-use-in-children [accessed 13 August 2026]

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication. In emergency situations involving severe allergic reactions with breathing difficulty or anaphylaxis, call 999 immediately.

Trusted by thousands

Real people, real results

Jane L.

"Brilliant. Lost 4 stone on mounjaro no side effects at all. Cured pharmacy are excellent. Always helpful pens sent out quickly always comes with needles and sterile wipes. If you want to go on GLP-1 go to cured pharmacy. So professional. Thank you cured pharmacy you changed my health and well being."

Ann-Marie

"I absolutely love this product, I have been using 2.5mg as maintenance dose and have managed to control my weight without any side effects and can still eat well balanced meals. The pharmacy is very efficient friendly and helpful I would not purchase from anywhere else."

Sacha W.

"So far I'm really impressed by my results it's crazy cause I'm not snacking like how I used to do and I see my face slimming down already and it's only been 2 and a half weeks. Can't wait to give my feedback in 5 months time thank you cured pharmacy."

Kimberly G.

"Mounjaro has corrected my hormonal weight gain during menopause. I am using it now to maintain that balance. The results for me have been exceptional!"

Jennifer

"Great really helps cure those nasty habits can't wait for my next mounjaro pen."

How it Works?

Select from our recommended UK-licensed medications.

1

Choose your treatment

Step 1: Choose your treatment from Cured Pharmacy

Select safe UK treatments. Quick answers.

2

Answer quick questions

Step 2: Answer quick consultation questions

We will deliver direct to you as quickly as tomorrow.

3

Get it delivered fast

Step 3: Fast discreet delivery to your door

Faq

What is the correct promethazine hydrochloride dosage UK adults should take?
Adults typically take 25mg at night for allergies, or 10-20mg two to three times daily, with a maximum of 100mg in 24 hours. Always follow your prescriber's specific instructions based on your condition and medical history.
Can I give promethazine to children in an emergency?
Children aged 5-10 years may take 10-25mg daily in divided doses, but children under 5 years should not receive promethazine except under specialist supervision due to respiratory depression risks. Always consult a healthcare professional before giving antihistamines to children.
How quickly does promethazine work for allergic reactions?
Oral promethazine typically begins working within 20-60 minutes, with peak effects at 2-3 hours. For severe allergic reactions with breathing difficulty or swelling, call 999 immediately — promethazine is not appropriate for anaphylaxis.
What is the difference between Phenergan tablets and Phenergan Elixir?
Both contain promethazine hydrochloride at the same strength per dose. Elixir (liquid) allows flexible dosing for children and those who cannot swallow tablets, while tablets offer convenience for standard 25mg adult doses.
Can I drive after taking promethazine?
No. Promethazine causes significant drowsiness that can impair driving ability for 12-24 hours after dosing. The MHRA specifically warns against driving or operating machinery whilst taking this medication.
Is promethazine available without prescription in the UK?
Promethazine is a pharmacy (P) medicine in the UK, meaning it can be supplied by pharmacists without prescription for specific indications in adults and children over 2 years. However, online supply requires a clinical assessment by a UK prescriber to ensure safe and appropriate use.
What should I do if I take too much promethazine?
Promethazine overdose can cause severe drowsiness, confusion, seizures, or respiratory depression. Seek immediate medical attention by calling 999 or attending A&E, bringing the medication packaging with you.
Can I take promethazine with other hay fever medications?
Avoid combining promethazine with other sedating antihistamines, but it may be used cautiously with non-sedating types like cetirizine under prescriber guidance. Always disclose all medications during your clinical assessment to identify potential interactions.
Tarun Kumar, Prescribing Pharmacist

Medically reviewed by

Tarun Kumar, Prescribing Pharmacist (GPhC 2233073)

Reviewed on: June 03, 2026

Last reviewed: 13 August 2026

Last updated on 13 August 2026.

Review History

Our experts continually monitor new findings in health and medicine, and we update our articles when new information becomes available.

Why this page was updated on 13 August 2026

Content checked and updated as part of our periodic review, to ensure accuracy and currentness.

Current version (13 August 2026)

Edited by: The Editorial Team

Medically reviewed by:

Tarun Kumar, GPhC No. 2233073, Prescribing Pharmacist


How we source info.

When we present you with stats, data, opinion or a consensus, we'll tell you where this came from.