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Trihexyphenidyl (Benzhexol)

This fact sheet has been written for parents and carers about the use of trihexyphenidyl (benzhexol) for movement disorder (dystonia) or control of secretions (drooling) in children.

This information sometimes differs from that provided by the manufacturers, because their information is usually aimed at adult patients. Please read this information carefully and keep it somewhere safe so that you can read it again.

Medicine names in Australia are changing to be the same as those used elsewhere in the world. In this fact sheet you will see that benzhexol has a second name, trihexyphenidyl. These are the same medicine and you will need to be familiar with both names as well as the brand name from the manufacturer. By 2023 the label on the bottle from the manufacturer and the label from the pharmacy will change to trihexyphenidyl.

ALERT: 
Do not stop trihexyphenidyl (benzhexol) abruptly. This can lead to a condition called Neuroleptic Malignant Syndrome that causes high temperatures, severe rebound muscle stiffness, sweating and increased heart rate. If this occurs call an Ambulance on 000 immediately. Any dose changes must be directed by a doctor and the dose must be reduced slowly over a period of time.

Trihexyphenidyl (Benzhexol) is also known as the brand name:

  • ARTANE®: 2 mg and 5 mg tablets

Artane® is available from your local community or hospital pharmacy with a prescription.

Why is it important for my child to take this medicine?

This medicine has been suggested for your child as they have been diagnosed with dystonia. Dystonia is a movement disorder which causes involuntary muscle contractions with twisting movements or abnormal postures. Trihexyphenidyl (Benzhexol) can relax these dystonic, constantly tensed muscles (or reduce dystonic movements). This may lead to benefits in your child’s comfort or function, or make it easier to move your child into different positions.

Smaller doses of trihexyphenidyl (benzhexol) are used to improve drooling by reducing the amount of saliva produced in the mouth.

It is also commonly used in adults with Parkinson’s disease. Trihexyphenidyl (Benzhexol) is part of the anticholinergic family of medicines and is thought to act by increasing levels of dopamine in the deep parts of the brain called the basal ganglia.

This medicine does not work for everyone. It is important to try this medicine over a period of weeks to months to see if there is improvement.

When should I give trihexyphenidyl (benzhexol)?

Trihexyphenidyl (Benzhexol) is usually started at a low dose to avoid side effects, and slowly increased until a good response is seen. It can be given once, twice, three or four times each day depending upon your child’s age, weight and condition and your doctor will advise on how often is best for your child.

How much should I give?

Trihexyphenidyl (Benzhexol) dosing is different for each patient. Your doctor will work out the amount of trihexyphenidyl (benzhexol) that is right for your child.

Your doctor will ask you how well the medicine is working, and may suggest that you change the amount you give, or when you give it, to get the best effect. If you think the dose is not right, talk to your doctor.

It is important that you follow your doctor’s instructions about how much to give.

Dosage Plan (for tablet administration):

Patient name:
UR Number: Date of Plan:
Date of Birth: Prescriber Name:
Use Trihexyphenidyl (Benzhexol) _______ mg tablets to make up the doses below
Week 1
Date: __________
Week 2
Date: __________
Week 3
Date: __________
Week 4
Date: __________
Morning ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg
Lunch ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg
Dinner ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg
Bedtime ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg ____ tablets = ____ mg

How should I give it?

Trihexyphenidyl (Benzhexol) can be given with or without food. Some people become very thirsty from this medicine. For these people, it can help to take the medicine before food.

Tablets should be swallowed with a glass of water or milk.

Tablets can be cut in half or crushed and mixed with liquid to be given via mouth or feeding tube. Do not mix with fruit juice or acidic foods. Your pharmacist can provide you with details on how to administer crushed or partial tablets.

When should the medicine start working and how will I know?

Because the medicine is started at a low dose, it may take several weeks to see changes.

For movement disorders (dystonia), you will know that the medicine is working if your child has some relaxation of their stiff muscles and feels more comfortable than before.

For control of secretions (drooling), you will know that the medicine is working if you can see less drool appearing in your child’s mouth, or your child is more thirsty than normal.

What if my child vomits?

  • If your child vomits less than 30 minutes after having a dose of trihexyphenidyl (benzhexol), give them the same dose again.
  • If your child vomits more than 30 minutes after having a dose of trihexyphenidyl (benzhexol), you do not need to give them another dose. Wait until the next normal dose.

If your child vomits again or misses several doses in a row, contact your doctor or hospital immediately. They will decide what to do based on your child’s condition.

What if I forget to give it?

Give the missed dose as soon as you remember during the day, provided:

  • There is still at least 12 hours before the next dose is due for children taking trihexyphenidyl (benzhexol) once a day.
  • There is still at least eight hours before the next dose is due for children taking trihexyphenidyl (benzhexol) twice each day
  • There is still at least four hours before the next dose is due for children taking trihexyphenidyl (benzhexol) three or four times each day

Otherwise, skip the missed dose and give the next scheduled dose.

You do not need to wake up a sleeping child to give a missed dose. Never give a double dose of the medicine to catch up a missed dose.

What if I give too much?

If you think your child may have had too much trihexyphenidyl (benzhexol), take your child to hospital straight away or contact the Queensland Poisons Information Service on 13 11 26. Tell the doctor or person on the phone that your child may have had too much trihexyphenidyl (benzhexol).

Have the medication with you if you telephone for advice, or take it with you to the hospital, so that the doctor can see what has been given.

Are there any possible side effects?

We use medicines to make our children better, but sometimes they have other effects that we don’t want (side effects).

Side effects you must do something about
Take your child to the doctor if your child has:

  • Dry eyes, enlarged (big) pupils, blurred vision (if eyes become red, sore or have discharge, or your child is having difficulty seeing)
  • Urinary retention (passing less urine than normal or feeling that their bladder is full but can’t be emptied). If unable to pass urine when they need to, you must consult your doctor or go to the nearest Emergency Department.
  • Constipation (difficulty passing bowel motions, or pooing). The dose of trihexyphenidyl (benzhexol) may need to be reduced. Rare cases have been reported where intestinal muscles stop working (paralytic ileus) leading to very severe vomiting or constipation.

Take your child to the nearest Emergency Department or call 000 for an ambulance if any of the above symptoms are severe or concerning.

Other side effects you need to know about
If your child has any of these side effects, and you are concerned, take your child to the doctor.

  • Dry mouth. In some situations, this may make softening food for swallowing difficult. Taking sips of water may help with this. If your child is having significant difficulties swallowing, the dose of trihexyphenidyl (benzhexol) may need to be decreased.
  • Dizziness and nausea may occur. Vomiting is uncommon.
  • Nervousness is commonly reported in adult patients. In children, this may present as increased irritability and changes in personality. Confusion, hallucination and disorientation are rarely reported side effects.
  • Decreased sweating may mean your child’s body temperature increases in hot weather. It is important to avoid over-heating and vigorous exercise as this may lead to heat stroke. It is important to ensure adequate fluid intake.

Can other medicines be given at the same time as trihexyphenidyl (benzhexol)?

  • You can give your child medicines that contain paracetamol or ibuprofen (to treat pain and fever), unless your doctor has told you not to.
  • Trihexyphenidyl (Benzhexol) should not be taken with some other medicines that you get on prescription or over the counter including herbal or complementary medicines. Before starting on any new medicine, check with your doctor or pharmacist and tell them all the other medicines or products your child is taking.

Is there anything else I need to know about trihexyphenidyl (benzhexol)?

Stopping the medicine abruptly can be associated with potentially serious side effects. Trihexyphenidyl (Benzhexol) should therefore only be stopped gradually and you should talk to your doctor about how the medicine should be weaned. Your doctor will advise you how often and by how much to reduce your child’s dose.

Where should I keep this medicine?

  • Keep trihexyphenidyl (benzhexol) in a cupboard away from heat and direct sunlight.
  • Make sure that children cannot see or reach the medicine.
  • Keep the medicine in the container it came in.

General advice about medicines

  • Try to give the medicine at about the same times each day. This will help you remember to give it every day.
  • Only give this medicine to your child. Never give it to anyone else, even if their condition appears to be the same, as this could do harm.
  • If you think someone else may have taken the medicine, contact your doctor or the Queensland Poisons Information Centre on 13 11 26 straight away.
  • Make sure that you always have enough medicine. Order a new prescription at least two weeks before you will run out.
  • Make sure that the medicine you have at home has not reached the ‘best before’ or ‘use by’ date on the packaging. Give old medicines to your pharmacist to dispose of appropriately.

Who to contact for more information

Your doctor, pharmacist or nurse will be able to give you more information about trihexyphenidyl (benzhexol) and about other medicines used to treat dystonia or control excess secretions.

Contact us

Pharmacy Department
Level 2, Queensland Children’s Hospital
501 Stanley Street, South Brisbane 4101
t: 07 3068 1901

In an emergency, always contact 000 for immediate assistance.

Fact sheet developed by Rehabilitation Medical Team and Pharmacy Department, Queensland Children’s Hospital. Updated: November 2019.

The primary source for the information in this fact sheet is the Australian Medicines Handbook Children’s Dosing Companion and UK Medicines for Children.
For details on any other sources used to create this fact sheet, please contact us via CHQMedicationSafety@health.qld.gov.au.

We take great care to make sure that the information in this fact sheet is correct and up-to-date. However, medicines can be used in different ways for different patients. It is important that you ask the advice of your doctor or pharmacist if you are not sure about something.
This fact sheet is about the use of these medicines in Australia, and may not apply to other countries. Children’s Health Queensland Hospital and Health Service cannot be held responsible for the accuracy of information, omissions of information, or any actions that may be taken as a consequence of reading this fact sheet.

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