Nytol One-A-Night 50mg Tablets (Pack of 20)

Nytol One-A-Night 50mg Tablets are a pharmacy sleep aid containing diphenhydramine hydrochloride 50 mg per tablet. They are licensed as an aid to the relief of temporary sleep disturbance in adults, taken as a single tablet shortly before bed. As a Pharmacy (P) medicine, this product is sold with a brief suitability check rather than on open shelves.

What is Nytol One-A-Night?

Nytol One-A-Night is an over-the-counter sleep aid whose active ingredient, diphenhydramine, is a sedating (first-generation) antihistamine. Alongside its antihistamine action it has anticholinergic and marked sedative effects, which is what makes it useful for short-term sleeplessness. Each white tablet is embossed “50” and contains 50 mg of diphenhydramine hydrochloride — the higher of the two Nytol tablet strengths (see the comparison below).

What is Nytol used for?

These tablets are licensed for one purpose only: to help with temporary sleep disturbance — the occasional bad nights that come with a change of routine, a noisy environment, jet lag or a short-lived stressful patch. They are intended for short-term use, not as a long-term answer to ongoing insomnia. If your sleeplessness persists for more than a couple of weeks it can occasionally signal an underlying medical problem, so speak to your pharmacist or doctor rather than continuing to self-treat. The NHS has helpful, drug-free advice on improving sleep and managing insomnia.

How does it work?

Diphenhydramine blocks histamine H1 receptors in the brain. Histamine is one of the chemicals that helps keep you awake and alert, so damping its effect brings on drowsiness, reduces the time it takes to fall asleep and can improve the depth and quality of sleep. The effect is felt soon after a dose — sedation is usually at its strongest one to three hours after taking a tablet.

How to take Nytol One-A-Night

• Adults and children over 16: take one tablet about 20 minutes before going to bed.
• Do not exceed the stated dose — one tablet in any 24 hours.
• Do not use for longer than two weeks without speaking to a doctor.
• Swallow with water. It is not for children under 16.

Because the sedative effect can linger, only take a tablet when you can allow a full night’s sleep.

How long does it take to work?

Diphenhydramine is absorbed quickly, with the sedative effect typically peaking within one to three hours — which is why it is taken shortly before bed. The elimination half-life is around 2 to 9 hours, so some people notice next-morning drowsiness (“hangover” effect). If that happens, do not drive or operate machinery until you feel fully alert.

Side effects of this sleep aid

The most common effects are an extension of what the tablet is designed to do — drowsiness and sedation — along with dry mouth, fatigue, dizziness, unsteadiness and reduced concentration. Less commonly it can cause blurred vision, a faster heartbeat, difficulty passing urine, or (particularly in older people) confusion or paradoxical restlessness. Tolerance to the sedative effect can develop with continued use, which is another reason to keep courses short. Stop and seek advice if you have any sign of an allergic reaction such as rash, swelling or breathlessness.

Who should not take it

Do not take these tablets if you are hypersensitive to diphenhydramine, or if you have a stenosing peptic ulcer or pyloroduodenal obstruction. Use with caution — and check with a pharmacist first — if you have glaucoma, an enlarged prostate or trouble passing urine, epilepsy, myasthenia gravis, asthma, bronchitis or COPD, or liver or kidney problems. It is not recommended in pregnancy or while breastfeeding. Avoid alcohol, which increases drowsiness, and do not combine it with other antihistamine-containing products (including cough, cold and hay-fever remedies). Diphenhydramine can also interact with MAOI antidepressants, other sedatives, anticholinergic medicines and drugs handled by the CYP2D6 enzyme such as metoprolol and venlafaxine, so tell your pharmacist about everything you take. The tablets contain lactose.

Nytol Original vs One-A-Night

The Nytol range splits by strength and by how it is sold. Nytol Original contains diphenhydramine 25 mg and is a general-sale (GSL) product, usually taken as two tablets. Nytol One-A-Night delivers the same nightly dose in a single 50 mg tablet and is a Pharmacy (P) medicine. There is also a herbal alternative based on valerian for those who prefer a traditional herbal remedy. For a night-time cold or flu that is also disturbing sleep, a combination product such as Night Nurse may be more appropriate — ask your pharmacist which is right for you.

Buy this sleep aid online

Bury Healthcare Online is a UK GPhC-registered pharmacy (registration 1126145). Because diphenhydramine 50 mg is a Pharmacy medicine, you will answer a few short suitability questions before checkout so our pharmacy team can confirm it is appropriate for you. Browse the full range of sleeping aids and sleep support products, and contact our pharmacist if you would like advice before you buy.

Always read the label and the patient information leaflet before use. If your sleep does not improve, speak to your pharmacist or doctor.

Medically reviewed by Hassan Khan, MPharm, Independent Prescriber — Superintendent Pharmacist, Bury Healthcare Online (GPhC-registered pharmacy 1126145). Last reviewed: July 2026.

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