Promethazine is one of the oldest antihistamines still in everyday use, and most people know it by the brand name Phenergan. It turns up for hay fever, a rash, travel sickness and sleepless nights — which is exactly why it gets misused. Here is what it is actually licensed for, the real doses, and the one rule that matters more than any other.
Essentially, yes. Promethazine hydrochloride is the drug. Phenergan is the brand it is sold under in the UK. If a box says “Phenergan” on the front and “promethazine hydrochloride” underneath, you are looking at one medicine, not two.
It is a sedating (first-generation) antihistamine. The sedation is not a side effect that slipped through — for some of its licensed uses it is the entire point. It is also why it behaves so differently from “non-drowsy” hay fever tablets such as cetirizine or loratadine.
Everything below is taken from the manufacturer’s Summary of Product Characteristics — the legal licence document — for Phenergan 25 mg Tablets and Phenergan Elixir, both revised 19 June 2024.
The licence covers four distinct uses:
Note the wording on sleep: in adults, and short term. Promethazine is not a long-term sleeping tablet and is not intended to be taken night after night indefinitely.
There is also a promethazine injection, but that is a prescription-only medicine used in healthcare settings — not something you can buy over the counter.
Phenergan must not be given to a child under 6. Both licences state plainly that “Phenergan is contraindicated for use in children less than 6 years of age”, and they give the reason: the potential for fatal respiratory depression, along with psychiatric and central nervous system events.
This is an absolute contraindication, not a cautious footnote. It catches people out because the Elixir looks like a children’s medicine — it is sweet, orange-flavoured and sugar-free — but the under-6 limit applies to the liquid exactly as it does to the tablets. If you have promethazine at home and a child under 6 is unwell or unsettled at night, it is not the answer. Ask a pharmacist.
Doses differ by what you are treating, not only by age. These are the licensed doses. Always read the leaflet inside your own pack, and check with a pharmacist if anything is unclear.
Up to 12 hours. That is the figure in the licence for drowsiness, dizziness and blurred vision — and it is the part most people underestimate. Take 25 mg at 11pm and you may still be affected well into the following morning.
So, per the licence: if you feel drowsy or dizzy or your vision is blurred, do not drive or operate machinery. Driving while impaired by a medicine is an offence in Great Britain whether or not you needed a prescription for it. Alcohol should be avoided during treatment — the two together compound the sedation.
It is contraindicated if you have had an allergic reaction to it before, in coma or central nervous system depression, and alongside monoamine oxidase inhibitors (a class of antidepressant). Beyond those, a pharmacist will want to know about other sedating medicines, breathing problems, glaucoma, prostate problems, epilepsy, liver disease, and whether you are pregnant or breastfeeding.
If your main problem is hay fever during the day, a non-sedating antihistamine is usually the better tool — you get the antihistamine effect without losing your afternoon. Promethazine earns its place when the sedation is either wanted, or worth it.
Both the tablets and the Elixir are Pharmacy (P) medicines — that is the legal category printed in the licence itself. A P medicine cannot be taken off an open shelf; it has to be sold by, or under the supervision of, a pharmacist. The short conversation about age, other medicines and what you are treating is the legal safeguard, not a formality.
Bought over the counter as a short-term sleep aid, we supply it to adults aged 16 and over, in line with how sedating antihistamine sleep products are sold.
We are a community pharmacy on Woodsley Road, serving Hyde Park, Woodhouse, Burley and Headingley. If you are not sure whether promethazine is right for you — or whether something else would suit you better — walk in and ask, or call us on 0113 244 1551. Advice is free and you are never obliged to buy anything. You can also find our opening hours and directions, or browse our sleep and stress range.
Yes — Phenergan is the brand name, promethazine hydrochloride is the active medicine.
No. It is contraindicated under 6 years of age because of the risk of fatal respiratory depression. Speak to a pharmacist or your GP about the underlying problem instead.
For short-term sleep the licensed dose is a single night-time dose. Because effects can persist up to 12 hours, take it early enough that you have a full night ahead of you.
No — the licence says alcohol should be avoided during treatment.
It is licensed for short-term use only. If you are still not sleeping after a few nights, that is worth a proper conversation rather than another packet.
