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Trihexyphenidyl Hydrochloride 5mg/5ml Syrup – patient leaflet, side effects, dosage

Last updated: · Text from the MHRA, as of · About this document

Medicine status: Prescription only (POM) Details

Medicine strength:
5 mg / 5 ml (1 mg/ml)
Other strengths and forms:
Contains active substance:

Patient leaflet - Trihexyphenidyl Hydrochloride 5 mg / 5 ml syrup

1. What Trihexyphenidyl Syrup is and what it is used for

Trihexyphenidyl Syrup belongs to a group of medicines called antimuscarinics.

Trihexyphenidyl Syrup is used to treat some of the symptoms of Parkinson's disease such as shakiness or stiffness of the muscles which can cause difficulty moving.

Some medicines can cause side effects which are like the symptoms of Parkinson's disease and it is also used to reduce these side effects.

2. What you need to know before you take Trihexyphenidyl Syrup

Do not take Trihexyphenidyl Syrup:

  • if you are allergic to trihexyphenidyl hydrochloride or any of the other ingredients of this medicine (listed in section 6) or to similar medicines such as orphenadrine hydrochloride or procyclidine hydrochloride.

Do not give Trihexyphenidyl Syrup to children.

Warnings and precautions

Talk to your doctor before taking Trihexyphenidyl Syrup if:

  • you have glaucoma (increased pressure in the eye)
  • you suffer from high blood pressure
  • you suffer from kidney, heart, liver, bowel or prostate problems
  • you suffer from digestive system or stomach problems
  • you suffer from bladder problems or have difficulty passing urine
  • you suffer from a condition called myasthenia gravis (a rare muscle weakness disorder)
  • you experience unusual movements of the face and tongue as this may be a sign of a serious condition known as tardive dyskinesia
  • you are elderly - this medicine should be used with caution and may cause confusion, delusions and hallucinations.

If any of the above applies to you, or if you are not sure, speak to your doctor or pharmacist before you take Trihexyphenidyl Syrup.

Other medicines and Trihexyphenidyl Syrup

Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines including medicines obtained without a prescription. Tell your doctor or pharmacist if you are taking or have taken any of the following medicines as they may interfere with Trihexyphenidyl Syrup:

  • other medicines that have an anti-muscarinic effect such as atropine, hyoscine, oxybutynin and tolterodine used to treat bowel or bladder problems
  • monoamine oxidase inhibitors (MAOIs) used to treat depression, for example isocarboxazid, moclobemide or phenelzine
  • antihistamines used to treat allergies, for example diphenhydramine
  • disopyramide used to treat irregular heartbeat
  • phenothiazines used to treat psychoses or nausea and vomiting, for example chlorpromazine or thioridazine
  • tricyclic antidepressants used to treat depression for example amitriptyline
  • metoclopramide or domperidone used to treat the symptoms of nausea
  • nefopam used to treat pain
  • other medicines used in the treatment of Parkinson's disease for example amantadine and levodopa
  • clozapine used to treat schizophrenia
  • parasympathomimetic medicines used for the treatment of urine retention, for example neostigmine or bethanechol.

If you are not sure if any of the above apply to you, talk to your doctor or pharmacist before taking Trihexyphenidyl Syrup.

Pregnancy, breast-feeding and fertility

Do not take Trihexyphenidyl Syrup if you are breast-feeding.

Tell your doctor if you are pregnant, trying to become pregnant or are breast-feeding.

Driving and using machines

Taking Trihexyphenidyl Syrup may make your vision blurred or make you feel less alert than usual. If you are affected you should not drive or use machines until the effect has worn off.

Trihexyphenidyl Syrup contains sucrose, ethanol, propylene glycol and sodium benzoate

  • sucrose - there is 2.6g of sucrose in every 5ml of syrup. The maximum dose of

    Trihexyphenidyl Syrup supplies 10.4g sucrose. This should be taken into account in patients with diabetes mellitus. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product.

  • ethanol – this medicine contains 0.817 mg of alcohol (ethanol) in each 5 mL, which is equivalent to 0.1634 mg/ml. The amount in 5mL of this medicine is equivalent to less than 1 ml beer or 1 ml wine. The small amount of alcohol in this medicine will not have any noticeable effects.
  • propylene glycol - this medicine contains 19.27mg propylene glycol per 5ml of syrup. If you are pregnant or breast-feeding or if you suffer from a liver or kidney disease, do not take this medicine unless recommended by your doctor. Your doctor may carry out extra checks while you are taking this medicine
  • sodium benzoate – this medicine contains 5.9 mg sodium benzoate in each 5ml, which is equivalent to 1.18 mg/ml.
  • sodium – this medicine contains less than 1mmol sodium (23 mg) per 5mL, that is to say essentially ‘sodium-free’.

    Continued overleaf E1V74RBJ3

Trihexyphe

APPROVALS

Third Party Approval Required YES

TICK APPLICABLE BOX

Name:

Signature: Date:

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50

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NO

Authority Approval Supplied YES

TICK APPLICABLE BOX

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Regulatory Sign-off

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Signature: Date:

E1V74RBJ3

3. How to take Trihexyphenidyl Syrup

Always take this medicine exactly as your doctor has told you. Check with your doctor or pharmacist if you are not sure.

The usual dose starts with 2mg (2ml) per day. This may be increased by your doctor gradually to a maximum of 20mg (four 5ml spoonfuls) a day.

If you take more Trihexyphenidyl Syrup than you should

If you accidentally take too much syrup, or someone else takes any of your medicine, you should tell your doctor at once or contact the nearest casualty department. Show any left-over medicines or the empty container to the doctor.

If you forget to take Trihexyphenidyl Syrup

Do not worry. If you forget to take a dose, take it as soon as possible, unless it is almost time to take the next dose (within 1-2 hours). DO NOT take a double dose. Then go on as before.

If you stop taking Trihexyphenidyl Syrup

Do not stop taking this medicine suddenly as your symptoms may get worse. If you want to stop taking Trihexyphenidyl Syrup ask your doctor who will tell you how to reduce the dose gradually.

If you have any further questions on the use of this product, ask your doctor or pharmacist.

4. Possible side effects

Like all medicines, this medicine can cause side effects, although not everyone gets them. Allergic reactions may occur rarely, with symptoms such as rash, itching, swelling of the face, wheeziness, shortness of breath, tightness in the chest, fever, low blood pressure and feeling dizzy particularly when standing up. If any of these occur STOP taking the medicine and contact a doctor immediately.

Trihexyphenidyl Syrup sometimes causes the following side effects in some people:

  • dry mouth, difficulty swallowing
  • constipation, feeling or being sick
  • blurred vision, large pupils, lack of near vision, eye discomfort, increased sensitivity to light and painful increased pressure in the eye
  • feeling agitated or nervous
  • confusion
  • hallucinations
  • feeling optimistic
  • inability to sleep or restlessness
  • forgetfulness
  • paranoid delusions (being worried that something bad is happening without any reason)
  • redness and dryness of the skin or skin rashes
  • difficulty passing urine or unable to pass urine
  • feeling thirsty
  • fever (raised body temperature)
  • faster heartbeat
  • worsening of myasthenia gravis (very tired or weak muscles).

Reporting of side effects

If you get any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at www.mhra.gov.uk/Yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

5. How to store Trihexyphenidyl Syrup

  • Keep Trihexyphenidyl Syrup out of the sight and reach of children.
  • Do not store above 25°C. Do not refrigerate or freeze. Store in the original package.
  • Do not use this medicine after the expiry date which is stated on the carton and bottle label (exp: month, year). The expiry date refers to the last day of that month.
  • Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.

6. Contents of the pack and other information

What Trihexyphenidyl Syrup contains

The active substance is trihexyphenidyl hydrochloride.

Each 5ml of Trihexyphenidyl Syrup contains 5mg trihexyphenidyl hydrochloride. The other ingredients are citric acid, sodium benzoate, propylene glycol, glycerol, ethanol, blackcurrant flavour, sucrose and water.

See Section 2 'Trihexyphenidyl Syrup contains sucrose, ethanol, propylene glycol and sodium benzoate'

What Trihexyphenidyl Syrup looks like and contents of the pack

Trihexyphenidyl Syrup is a colourless syrup available in bottles of 200ml.

Marketing Authorisation Holder and Manufacturer

Rosemont Pharmaceuticals Ltd, Rosemont House, Yorkdale Industrial Park, Braithwaite Street, Leeds, LS11 9XE, UK.

This leaflet was last revised in: October 2022

About this document

Source: MHRA - Medicines and Healthcare products Regulatory Agency (products.mhra.gov.uk) · Marketing authorisation: PL 00427/0222

Last revision stated in the text: October 2022 · MHRA data as of 13 October 2026

Found a mistake? Tell us on the contact page.

The information on this site does not replace the advice of a doctor or pharmacist.

Facts about Trihexyphenidyl Hydrochloride 5 mg / 5 ml syrup

Prescription needed? Yes, prescription-only medicine (POM)
Active substance Trihexyphenidyl
Strength 5 mg / 5 ml (1 mg/ml)
Pharmaceutical form Oral solution
How is it taken Oral
Excipients Monohydrate citric acid, sodium benzoate, propylene glycol, glycerol, ethanol, blackcurrant flavour, sucrose and purified water.
Pack sizes 200 ml
Is it available? Listed as available (NHS Dictionary of Medicines and Devices – not a record of current supplies)
Shelf life 24 months.
Drug group (ATC) Anti-cholinergic agents
  1. N Nervous system drugs
    1. N04 Anti-parkinson drugs
      1. N04A Anticholinergic agents
        1. N04AA Tertiary amines, anticholinergic
          1. N04AA01 trihexyphenidyl
Marketing authorisation PL 00427/0222 (first authorised 30 June 1999)
Marketing authorisation holder Rosemont Pharmaceuticals Ltd
Codes GTIN 5016119293498 · BNF 04090200

Sources: the MHRA product information (products.mhra.gov.uk) and the NHS Dictionary of Medicines and Devices (dm+d), release 10.2.0 of 19 October 2026, NHS Business Services Authority. Contains public sector information licensed under the Open Government Licence v3.0.