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Histergan Tablets

Active Ingredient:
diphenhydramine hydrochloride
Norma Chemicals Limited See contact details
ATC code: 
About Medicine
The Patient Information Leaflet (PIL) is the leaflet included in the pack with a medicine.
Last updated on emc: 21 Nov 2019

Below is a text only representation of the Patient Information Leaflet (ePIL).

The text only version may be available in large print, Braille or audio CD. For further information call emc accessibility on {phone} 0800 198 5000. The product code(s) for this leaflet is: PL 00386/5008.

Histergan Tablets

Patient Information Leaflet

histergan tablets

Diphenhydramine Hydrochloride

Please read this leaflet carefully before using this medicine. If you have any questions or are not sure about anything, ask your doctor or pharmacist.

This leaflet contains the following information.

1. What are Histergan Tablets and what do they do?
2. What should I know before using Histergan Tablets?
3. How do I use Histergan Tablets?
4. Do Histergan Tablets have any side effects?
5. How do I store Histergan Tablets?
6. Further information.

1. What are Histergan Tablets and what do they do?

Histergan Tablets contain the following active ingredient: Diphenhydramine hydrochloride. Diphenhydramine hydrochloride is an antihistamine which works by blocking the body’s response to histamine, which is an agent responsible for causing allergic responses such as hay fever, stings and rashes. Histamine is also involved in the brain’s waking system so diphenhydramine hydrochloride can help alleviate temporary sleeplessness.

2. What should I know before using Histergan Tablets?
When shouldn’t I use Histergan Tablets?

Do not take Histergan Tablets if you are allergic to any of the ingredients listed in section 6 of this leaflet.

Do not take Histergan Tablets if you suffer from porphyria.

What else should I be aware of before using Histergan Tablets?

You should inform your doctor or pharmacist before taking this medicine if any of the following apply:

  • You are an asthmatic.
  • You suffer from prostate problems, epilepsy, glaucoma or liver disease.
  • You suffer from urinary retention.
Can I use Histergan Tablets if I am pregnant or breastfeeding?

Do not take Histergan Tablets if you are pregnant or breast feeding.

Is it safe to drive or operate machinery after using Histergan Tablets?

Histergan Tablets may cause drowsiness. Do not drive or operate machinery.

Are there any foods or medicines that interact with Histergan Tablets?

While taking Histergan Tablets:

  • Avoid alcoholic drink.

Consult your doctor or pharmacist before taking Histergan Tablets if you are taking any of the following:

  • Any other antihistamines (e.g. allergy treatments and cold remedies).
  • Any other products to help you sleep.
  • Medicines for anxiety.
  • Betahistine (used to treat balance disorders such as Ménière’s disease).
3. How do I use Histergan Tablets?
For the treament of hay fever, stings, rashes and other minor allergies:

Adults and children over 12 years: 1 or 2 tablets three or four times a day or as prescribed by a doctor.

Not recommended for children under 12 years of age.


For use as a temporary sleep aid:

Adults: 1 or 2 tablets to be taken at bedtime or after retiring when sleep is not readily achieved.

Do not take a repeat dose in the same night.

Not recommended as a sleep aid in children under 16 years of age.


What should I do if I accidentally swallow too many Histergan Tablets?

Seek medical attention as soon as possible. When seeking medical advice you should, if possible, take the medicine and this leaflet with you provided it doesn’t cause a delay.

4. Do Histergan Tablets have any side effects?

All medicines can cause side effects.

Very rarely diphenydramine hydrochloride may cause bruising and/or bleeding. If you suffer from spontaneous bruising or bleeding discontinue treatment and seek immediate advice from your doctor.

The following side effects have also been reported to the ingredients of Histergan Tablets:

  • Dizziness, drowsiness, poor co-ordination.
  • Confusion, depression, numbness, tremors.
  • Excitability (usually restricted to children).
  • Dryness of the mouth, headache, blurred vision, difficulty in urinating.
  • Nausea, vomiting, diarrhoea.
  • Heart palpitations.
  • Allergic reactions such as skin rashes.
  • Photosensitivity (sun allergy).
  • Convulsions, sweating, muscle pains.
  • Low blood pressure.
  • Hair loss.
  • Jaundice.

If you experience any severe side effect, or have a side effect which isn’t listed, then discontinue use and seek the advice of your doctor or pharmacist.

Reporting of side effects

If you get any side effects, talk to your doctor or pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at By reporting side effects you can help provide more information on the safety of this medicine.

5. How do I store Histergan Tablets?

Do not use after the expiry date marked on the pack. Keep all medicines out of the reach and sight of children, preferably in a locked cupboard. Store below 25°C.

6. Further information.
What is in Histergan Tablets?

Each tablet contains 25mg of the active ingredient diphenhydramine hydrochloride. In addition Histergan Tablets also contain the following non-active ingredients: lactose, corn starch, polyvinylpyrolidone, magnesium stearate, polyvinylcetate phthalate, ethyl acetate, stearic acid, sucrose, calcium carbonate, talc, acacia, carnauba wax, beeswax, silicone fluid and colourings E171 (titanium dioxide) and E127 (erythrosine).

How are Histergan Tablets supplied?

Histergan Tablets are supplied in packs of 20 tablets.

Who is responsible for Paxidorm Tablets?

The marketing authorisation holder is:

Norma Chemicals Ltd.
51-53 Stert Street
OX14 3JF

The manufacturer is:

Surepharm Services Limited
Bretby Business Park
Ashby Road
East Burton upon Trent
DE15 0YZ

This Leaflet was revised July 2015


Norma Chemicals Limited
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51-53 Stert Street, Abingdon, Oxon, OX14 3JF
Medical Information Direct Line
+44 (0)1235 538 700
Medical Information e-mail
[email protected]
Customer Care direct line
+44 (0)1235 538 700
Medical Information Fax
+44 (0)1235 538 800
Adverse event reporting email
+44 (0)1235 538 700