Diphenhydramine is an antihistamine sometimes used as a sleeping pill. It's available to buy without a prescription from a doctor. It is also an ingredient in some over-the-counter cold and flu medicines and sleep aids, such as Benylin, Nytol and Boots Sleapeaze.
You can find detailed information about promethazine in the official Patient Information Leaflet (PIL), including what it's for, how to take it, possible side effects and safety information. This leaflet should come with your medication (usually inside the box). You can also access it online as a PDF by clicking this link:
If a drug can come in different forms (such as tablets or liquid), there may be a separate PIL for each one. You should look at the PIL for the particular form and dose you've been prescribed. All PILs are available online on the electronic Medicines Compendium (eMC).
Even though this drug is available without a prescription, it's a good idea to check with the pharmacist that it's suitable for you before buying it.
See our page on what you need to know before taking any medication for a list of issues you might want to go through with them. Most high street pharmacists have a private consulting room you can ask to use if you don't feel comfortable discussing these issues over the counter.
If you have any questions about your medication you can talk to your doctor, someone at your pharmacy or call NHS 111.
What else might I want to know?
We're currently reviewing all of our medication pages. Please tell us what you would like to find on this page in future by clicking the 'tell us more' button below.
If you have personal experience of taking this drug and would be interested in producing a blog or vlog about it to appear alongside our information see our pages on telling your story.
Published April 2017.