Trihexyphenidyl

What is trihexyphenidyl?

Trihexyphenidyl is a medication that is used to treat abnormal muscle movements including spasms, tremors and stiffness. It works by relaxing the muscles.

You may also hear trihexyphenidyl called by its brand name, Artane®. Trihexyphenidyl comes in tablet form.

Talk with your child’s health-care provider if your child has any of the following conditions. Precautions may need to be taken with this medicine if your child has:

• a history of allergic reaction to trihexyphenidyl
• an eye condition called narrow-angle glaucoma
• myasthenia gravis, which is an immune condition that causes severe muscle weakness
• tardive dyskinesia, which is a severe muscle problem
• severe cardiovascular disease (disease of the heart or the blood vessels)
• kidney disease
• liver disease

How should you give your child trihexyphenidyl?

When giving your child trihexyphenidyl:

• Give trihexyphenidyl exactly as your health-care provider tells you, even if your child seems better.
• Talk to your child's health-care provider before you stop giving trihexyphenidyl for any reason. Stopping suddenly can make your child’s condition worse, or your child may experience more side effects.
• Give trihexyphenidyl with or without food at the same time(s) every day. Give with food if it upsets your child’s stomach.

When giving your child trihexyphenidyl tablets:

• The tablets should be swallowed whole, with water.
• If your child cannot swallow tablets whole, the tablets may be crushed and mixed into a small amount of water, milk or soft foods.

What should you do if your child misses a dose?

• Give the missed dose as soon as you remember.
• If it is almost time for the next dose, skip the missed dose. Give the next dose at the regular time.
• Do not give your child two doses to make up for one missed dose.

What are the possible side effects of trihexyphenidyl?

Your child may have some of these side effects while they take trihexyphenidyl.

Check with your child's health-care provider if your child continues to have any of these side effects, if they do not go away, or if they bother your child:

• dry eyes, mouth or nose
• blurred vision
• headache
• drowsiness, dizziness
• feeling weak
• trouble having a bowel movement
• decreased sweating
• agitation or restlessness
• difficulty sleeping
• change in mood or behaviour
• weight loss

Most of the following side effects are not common, but they may be a sign of a serious problem. Call your child's health-care provider right away or take your child to an Emergency Department if your child has any of these side effects:

• itching, hives, swelling of the throat, chest tightness or trouble breathing
• fever, stiff muscles and a fast or irregular heartbeat
• lack of sweating in very warm temperatures or during rigorous physical activity
• seeing or hearing things that are not there
• confusion or disturbing behaviour or thoughts
• very bad belly pain
• trouble passing urine
• trouble seeing or eye pain

What safety measures should you take when your child is using this medicine?

Trihexyphenidyl may cause your child to be dizzy, drowsy or less alert. Have your child avoid activities such as riding a bicycle, rollerblading, contact sports and using scissors until the effects of the medication in your child are known. Schoolwork may be more difficult for your child to focus on.

Trihexyphenidyl may make your child's mouth and throat dry. Sucking a hard, sugarless candy or chewing sugarless gum, if they are able to safely do so, will help your child feel more comfortable.

Trihexyphenidyl may make your child's eyes more sensitive to light than normal. They may feel more comfortable by wearing sunglasses and staying away from bright lights.

Trihexyphenidyl may make your child sweat less. This may cause their body temperature to rise. Be careful that your child does not become overheated during exercise or in hot weather while they are taking this medicine. Your child should drink lots of fluids, especially during warmer seasons and when exercising.

There are some medicines that should not be taken together with trihexyphenidyl, or, in some cases, the dose of trihexyphenidyl or the other medicine may need to be adjusted. It is important that you tell your child’s health-care providers if your child takes any other medications (prescription, over the counter or herbal) including:

• atropine eye drops
• medications used to help with gut motility (e.g., domperidone, cisapride)
• inhaled ipratropium or tiotropium
• glycopyrrolate
• potassium chloride tablets, potassium citrate

What other important information should you know?

• Keep a list of all medications your child is on and show the list to their health-care provider.
• Do not share your child’s medicine with others and do not give anyone else’s medicine to your child.
• Make sure you always have enough trihexyphenidyl to last through weekends, holidays and vacations. Call your pharmacy at least two days before your child runs out of medicine to order refills.
• Keep trihexyphenidyl tablets at room temperature in a cool, dry place away from sunlight. Do NOT store it in the bathroom or kitchen.
• Do not keep any medicines that are out of date. Check with your pharmacist about the best way to throw away outdated or leftover medicines.

Keep trihexyphenidyl out of your child’s sight and reach and locked up in a safe place. If your child takes too much trihexyphenidyl, call your local Poison Information Centre at one of these numbers. These calls are free. 

• Call 1-844 POISON-X, or 1-844-764-7669, from anywhere in Canada except Quebec.
• Call 1-800-463-5060 if you live in Quebec.