Patient Medication Information: uses, side effects, how to take - Trihexyphenidyl
What TRIHEXYPHENIDYL is used for:
TRIHEXYPHENIDYL is used in adults to:
- treat all forms of Parkinsonism (a movement disorder).
- prevent or control movement disorders caused by certain central nervous system drugs (e.g., reserpine and phenothiazines). This includes disorders that cause extreme restlessness, involuntary movements, or muscle spasms.
How TRIHEXYPHENIDYL works:
TRIHEXYPHENIDYL belongs to a group of medicines known as “antispasmodics”. The exact way it works is not known. However, it can help with muscle control and reducing stiffness making it easier to move.
The ingredients in TRIHEXYPHENIDYL are:
Medicinal ingredient: Trihexyphenidyl hydrochloride.
Non-medicinal ingredients: Croscarmellose sodium, lactose monohydrate, magnesium stearate, and microcrystalline cellulose.
TRIHEXYPHENIDYL comes in the following dosage form(s):
Tablets: 2 mg and 5 mg of trihexyphenidyl hydrochloride.
Do not use TRIHEXYPHENIDYL if:
- you are allergic to trihexyphenidyl hydrochloride or any of the other ingredients in TRIHEXYPHENIDYL.
- you have an eye disorder called narrow angle glaucoma (increased pressure in the eyes).
To help avoid side effects and ensure proper use, talk to your healthcare professional before you take TRIHEXYPHENIDYL. Talk about any health conditions or problems you may have, including if you:
- have heart or blood vessel problems.
- have high blood pressure.
- have gastrointestinal (GI) tract problems.
- have liver problems.
- have kidney problems.
- have prostate problems.
- have trouble passing urine.
- have a condition called myasthenia gravis (muscle weakness).
- have a condition called tardive dyskinesia (uncontrolled twitching and jerking, and other parts of the body).
are pregnant or plan to become pregnant.
- are 60 years of age or older.
have one of the following rare genetic conditions:
- Galactose intolerance,
- Lapp lactase deficiency, or
- Glucose-galactose malabsorption.
Lactose is a non-medicinal ingredient in TRIHEXYPHENIDYL.
- are breast-feeding or plan to breast-feed. It is not known if trihexyphenidyl hydrochloride is passed into breast milk).
- have ever had a negative reaction after taking other drugs in the past.
- have a fever.
- plan to do physical activity during your treatment or plan to be in a hot environment (e.g., manual labour in hot weather).
Other warnings you should know about:
Driving and using machines: TRIHEXYPHENIDYL may affect your mental and physical ability to drive and operating machinery. Before you drive or do tasks that require special attention, wait until you know how TRIHEXYPHENIDYL affects you.
- Eye problems: TRIHEXYPHENIDYL can affect your eyes and vision (e.g., difficulty focusing on objects, blurred vision, and pupil widening). Before your treatment, you should have an eye test called a gonioscope evaluation that checks for signs of glaucoma. Your eyes and vision will then be regularly monitored throughout your treatment.
Tell your healthcare professional about all the medicines you take, including any drugs, vitamins, minerals, natural supplements or alternative medicines.
The following may interact with TRIHEXYPHENIDYL:
- Alcohol.
- Amantadine, a medicine used to treat viral infections.
- Antihistamines, medicines used to treat Parkinson’s disease and allergies.
- Cannabinoids, medicines used to treat poor appetite, nausea, and sleep apnea.
- Disopyramide, a medicine used to treat irregular heartbeats.
- Levodopa, a medicine used to treat Parkinson’s disease.
- Nefopam, a medicine used to treat pain.
- Monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants, medicines used to treat depression.
- Other central nervous system (CNS) depressants (e.g., barbiturates), medicines used to slow down the brain and nervous system.
- Prokinetic agents (e.g., metoclopramide, domperidone, and tegaserod), medicines used to treat GI tract movement disorders.
- Opioids, medicines used to treat severe pain.
- Parasympathomimetics, medicines used to treat urinary retention.
- Phenothiazines, clozapine, neuroleptics, medicines used to treat certain mental illnesses.
- Anticonvulsants, medicines used to prevent and control seizures in the treatment of epilepsy.
- Carbonic anhydrase inhibitors (e.g., topiramate), medicines used to treat seizures and migraines.
- Magnesium hydrochloride, a medicine used for constipation and heartburn.
- Memantine, a medicine used to treat Alzheimer’s disease.
- Acidic foods (e.g., citrus and fruit juices).
- Coffee.
Ask your healthcare professional if you are unsure.
How to take TRIHEXYPHENIDYL:
- Always take TRIHEXYPHENIDYL exactly as your healthcare professional has told you to. Ask your healthcare professional if you are not sure.
The exact timing of your doses should be discussed with your healthcare professional. TRIHEXYPHENIDYL tablets is usually taken at meal times (just before or just after a meal).
- Do not adjust or stop taking TRIHEXYPHENIDYL suddenly as your symptoms may get worse. If your dose needs to be lowered or stopped, your healthcare professional will discuss how to properly reduce your dose.
Usual dose:
Your healthcare professional will decide the right dose and frequency for you. This may depend on your health condition, your age, and how you react to TRIHEXYPHENIDYL. You will normally start on a low dose and this may be gradually increased by your healthcare professional.
The usual dose is between 5 mg to 15 mg divided up in a day. If you are 60 years of age or older, you may need less than the usual dose.
Overdose:
| If you think you, or a person you are caring for, have taken too much TRIHEXYPHENIDYL, contact a healthcare professional, hospital emergency department, regional poison control centre, or Health Canada’s toll-free number, 1-844 POISON-X (1-844-764-7669) immediately, even if there are no symptoms. |
|---|
Missed dose:
If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the next dose at the regularly scheduled time.
Possible side effects from using TRIHEXYPHENIDYL:
These are not all the possible side effects you may have when taking TRIHEXYPHENIDYL. If you experience any side effects not listed here, tell your healthcare professional.
Side effects of TRIHEXYPHENIDYL may include:
- difficulty sleeping,
- dizziness,
- drowsiness,
- flushing,
- memory loss,
- dry mouth,
- feeling weak and tired,
- headache,
- restlessness,
- weight loss,
- dry skin,
- thirst,
- high body temperature,
- nervousness.
Serious side effects and what to do about them
| Frequency/Side Effect/Symptom | Talk to your healthcare professional | Get immediate medical help | |
|---|---|---|---|
| Frequency/Side Effect/Symptom | Talk to your healthcare professional | Get immediate medical help | |
| Only if severe | In all cases | ||
| Only if severe | In all cases | ||
| Very Common | |||
| Eye problems: dilated pupils, light sensitivity changes, increased pressure in the eyes, eye and head pain, swelling or redness in or around the eye, changes in vision, hazy or blurred vision, headaches, or sudden sight loss. | √ | ||
| Rare | |||
| Gastrointestinal (GI) tract problems: stomach pain, stomach discomfort, bloating, constipation, nausea, vomiting, loss of appetite, unable to pass gas or stool, cramps, difficulty swallowing, or feeling dehydrated. | √ | ||
| Mental and/or behavioural changes: confusion, agitation, aggression, defiant behaviour, loss of sleep, restlessness, delusions (a false belief, despite | √ | ||
| incontrovertible evidence, that something is false), hallucinations (seeing or hearing things that are not there), drowsiness, headache, loss of memory, decline in thinking, or paranoia (unrealistic and excessive anxiety, worry, distrust, and suspicion). | |||
| Unknown | |||
| Abnormally fast or slow heartbeat. | √ | ||
| Allergic reaction: difficulty swallowing, difficulty breathing, wheezing, drop in blood pressure, nausea, vomiting, hives, rash, or swelling of the face, lips, tongue, or throat. | √ | ||
| Angle-closure glaucoma (increased pressure in the eyes): vision changes, blurred vision, halos around lights, seeing rainbows around the eyes, sudden loss of sight, eye pain, eye redness, nausea, vomiting, or severe headache. | √ | ||
| Decreased bronchial secretions (less mucus in the lungs): dry cough, shortness of breath, feeling dehydrated, or chest pain. | √ | ||
| Kidney and urinary problems: difficulty peeing, trouble starting or slow urine flow, or unable to completely empty the bladder. | √ | ||
| Myasthenia gravis (muscle weakness): weakness of the muscles in the face, limbs, dropping of eyelids, fatigue, trouble walking, speaking, or swallowing. | √ | ||
| Neuroleptic malignant syndrome (a serious drug reaction): muscle stiffness or inflexibility with high fever, rapid or irregular heartbeat, sweating, state of confusion, reduced consciousness, increased breathing rate, or change in blood pressure. | √ | ||
If you have a troublesome symptom or side effect that is not listed here or becomes bad enough to interfere with your daily activities, tell your healthcare professional.
Reporting side effects
You can report any suspected side effects associated with the use of health products to Health Canada by:
NOTE: Contact your healthcare professional if you need information about how to manage your side effects. The Canada Vigilance Program does not provide medical advice. |
Storage:
Store TRIHEXYPHENIDYL at room temperature, 15°C to 30°C. Preserve in a tight container.
Keep out of reach and sight of children.
If you want more information about TRIHEXYPHENIDYL:
- Talk to your healthcare professional.
- Find the full Product Monograph that is prepared for healthcare professionals and includes the Patient Medication Information by visiting the Health Canada Drug Product Database website (https://www.canada.ca/en/health-canada/services/drugs-health-products/drug-products/drug-product-database.html); the manufacturer’s website (https://www.aapharma.ca/en/), or by calling 1-877-998-9097.
Date of Authorization: August 7, 2026