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Promethazine

Medication sedating antihistamine allergy
Aka: Phenergan
Brands seen in Singapore: Xepagan, Promagen, Axcel Promethazine, Promezine, Votazine
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Allergy symptoms, itch, nausea, motion sickness, sleep
When to take
HealthHub: when needed for symptoms, with or without food
Take with
Water · NHS: swallowed whole, and HealthHub: no alcohol
Pros & cons
Pros
  • HealthHub: eases itch, runny nose and sneezing
  • NHS: also used for motion sickness and vertigo
  • Sold at SG pharmacies without a prescription
Cons
  • HealthHub: drowsiness, dizziness, dry mouth
  • FDA: not for under-2s — fatal breathing risk
  • HealthHub: constipation, trouble passing urine
Sources
  1. HSA — Listing of Registered Therapeutic Products (data.gov.sg open dataset, 5,511 rows, cached locally at /tmp/hsa_all.json and filtered locally) · read 2026-08-27
    what it says
    “17 of 18 registered promethazine products carry Forensicclassification 'Pharmacy Only' — XEPAGAN · PROMAGEN · AXCEL PROMETHAZINE-5 · PROMEZINE · VOTAZINE TABLET 25 mg; only SIN02707P DBL PROMETHAZINE INJECTION 50 mg/2 ml reads 'Prescription Only'. No Phenergan row exists.”
  2. HealthHub (Pharmaceutical Society of Singapore) — Promethazine: what is this medication for · read 2026-08-27
    what it says
    “Promethazine belongs to a group of medicines known as antihistamines … Relief of itch in the eyes, nose or skin … Relief of runny nose and sneezing; Treat nausea and vomiting; Help you to fall asleep”
  3. HealthHub — Promethazine: how should I take or use this medication · read 2026-08-27
    what it says
    “This medication may be taken with or without food. Take this medication when necessary to relieve your symptoms. Do not exceed the maximum dose as recommended by your healthcare professional.”
  4. HealthHub — Promethazine: what precautions should I take · read 2026-08-27
    what it says
    “You are pregnant, planning to become pregnant, or breastfeeding … Increased eye pressure (glaucoma); Difficulty in urinating … Stomach ulcers; Seizures; Kidney, liver, respiratory or thyroid diseases; High blood pressure or abnormal heart rhythm”
  5. HealthHub — Promethazine: common side effects · read 2026-08-27
    what it says
    “Drowsiness or feeling tired … Dizziness … Dry mouth … Constipation … Headache; Difficulty in passing urine or constipation”
  6. HealthHub — Promethazine: what food or medication should I avoid · read 2026-08-27
    what it says
    “Avoid alcoholic drinks as this may increase drowsiness. Avoid taking sedating medications … Do not take with or within 14 days of stopping monoamine oxidase inhibitors (MAOIs). Many over-the-counter medications contain antihistamines”
  7. NHS Medicines A-Z — Promethazine (Phenergan): how to take it · read 2026-08-27
    what it says
    “Always take your promethazine tablets with a drink of water. Swallow them whole. Do not chew them. You can take promethazine with or without food.”
  8. NHS Medicines A-Z — Promethazine: dosage for hay fever or hives · read 2026-08-27
    what it says
    “For hay fever or hives the dose can vary from 10mg twice a day to 20mg 3 times a day or 25mg once or twice a day.”
  9. NHS Medicines A-Z — Promethazine: dosage for vertigo, and strengths · read 2026-08-27
    what it says
    “For vertigo the dose can vary from 25mg a day to 25mg 4 times a day. Promethazine tablets come in strengths of 10mg, 20mg or 25mg.”
  10. NHS Medicines A-Z — Promethazine: dosage for motion sickness · read 2026-08-27
    what it says
    “For preventing motion sickness you'll usually take 25mg the night before your journey … For treating motion sickness take 25mg as soon as possible and 25mg the same evening.”
  11. US FDA label for promethazine hydrochloride tablets USP, Dosage and Administration, via openFDA drug/label.json (effective 2024-10-30) · read 2026-08-27
    what it says
    “Allergy: The average oral dose is 25 mg taken before retiring; however, 12.5 mg may be taken before meals and on retiring, if necessary … Motion Sickness: The average adult dose is 25 mg taken twice daily.”
  12. US FDA label for promethazine hydrochloride tablets USP, Contraindications, via openFDA · read 2026-08-27
    what it says
    “Promethazine Hydrochloride Tablets, USP are contraindicated for use in pediatric patients less than two years of age … contraindicated in comatose state … Antihistamines are contraindicated for use in the treatment of lower respiratory tract symptoms including asthma.”
  13. US FDA label for promethazine hydrochloride tablets USP, Warnings (boxed warning text), via openFDA · read 2026-08-27
    what it says
    “Promethazine hydrochloride should not be used in pediatric patients less than 2 years of age because of the potential for fatal respiratory depression … The impairment may be amplified by concomitant use of other central-nervous-system depressants such as alcohol, sedatives/hypnotics”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.