Trihexyphenidyl is used to treat symptoms of Parkinson's disease (stiffness, tremors, spasms, poor muscle control).

Trihexyphenidyl is also used to treat and prevent Parkinson-like symptoms that are caused by using certain anti-psychotic medications.

Trihexyphenidyl may also be used for purposes not listed in this medication guide.

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Your doctor will tell you whether you should take trihexyphenidyl before or after a meal.

Take the medicine with food if it upsets your stomach.

If trihexyphenidyl causes your mouth to feel dry, you may need to take it before meals.

You may also use mints, chewing gum, or water if you have a very dry mouth or you feel very thirsty.

The pressure inside your eyes will need to be checked while you are taking trihexyphenidyl.

You should not stop using trihexyphenidyl suddenly. Stopping suddenly may make your condition worse.

Store at room temperature away from moisture, heat, and light. Do not freeze.

Usual Adult Dose for Extrapyramidal Reaction:

Initial dose: 1 mg orally once; if symptoms are not controlled in a few hours, additional doses should be provided until satisfactory control is achieved
Maintenance dose: 5 to 15 mg/day orally in divided doses; although some patients may benefit from 1 mg/day

Comments:
-Control of extrapyramidal symptoms (EPS) may be more rapidly achieved by temporarily reducing the dose of the responsible agent.
-After symptoms have been controlled for several days, it may be possible to reduce the dose of discontinue use; there are reports of EPS remaining in remission for long periods after this drug has been discontinued.

Use: For the control of extrapyramidal disorders caused by central nervous system drugs such as the dibenzoxazepines, phenothiazines, thioxanthenes, and butyrophenones.

Usual Adult Dose for Parkinson's Disease:

Initial dose: 1 mg orally once a day
-Titrate in 2 mg/day increments every 3 to 5 days
Maintenance dose: 6 to 10 mg orally in divided doses
Maximum dose: Some patients, particularly those with postencephalitic parkinsonism, may require 12 to 15 mg/day

Concomitant Use with Levodopa: 3 to 6 mg orally per day in divided doses
-When used concomitantly with levodopa, the dose of both drugs may need to be reduced
-Adjust doses based on side effects and symptom control

Comments:
-Doses should be individualized; start low and increase slowly, especially in elderly patients.
-The total daily dose may be better tolerated if given in divided doses; doses greater than 10 mg/day should be divided and given 4 times a day.
-The decision to dose before or after meals should be based on the needs of the patient; this drug does cause dry mouth and taking before meals may be beneficial, unless it causes nausea.

Use: For the adjunctive treatment of all forms of Parkinson's disease.

You should not use trihexyphenidyl if you are allergic to it, or if you have:

• narrow-angle glaucoma.

Tell your doctor if you have ever had:

• glaucoma;

• an enlarged prostate;

• urination problems;

• a bowel obstruction, severe constipation, or toxic megacolon;

• epilepsy or other seizure disorder;

• heart problems;

• coronary artery disease (clogged arteries);

• high blood pressure;

• alcoholism; or

• a problem with your nerves, brain, or spinal cord.

Older adults may be more sensitive to the effects of trihexyphenidyl.

Tell your doctor if you are pregnant or breast-feeding.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include severe drowsiness, fever, dilated pupils, feeling hot, paleness in your face, dry skin and mouth, hallucinations, paranoia, agitation, seizure, or numbness in or around your mouth, nose, or throat.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

Unless your doctor tells you otherwise, continue your normal diet.

Avoid becoming overheated or dehydrated during exercise and in hot weather. Trihexyphenidyl can decrease sweating and you may be more prone to heat stroke.

Avoid driving or hazardous activity until you know how trihexyphenidyl will affect you. Your reactions could be impaired.

Avoid using cannabis, CBD, or marijuana while taking trihexyphenidyl.

Avoid drinking alcohol. It may increase your risk of side effects.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Trihexyphenidyl may cause serious side effects. Call your doctor at once if you have:

• blurred vision, tunnel vision, eye pain, or seeing halos around lights;

• hot and dry skin, or a lack of sweating even if you feel hot;

• rapid or jerky repetitive involuntary movement;

• severe constipation;

• painful or difficult urination;

• unusual thoughts or behavior;

• confusion, memory problems; or

• severe nervous system reaction--very stiff (rigid) muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, feeling like you might pass out.

Common side effects of trihexyphenidyl may include:

• blurred vision;

• dry mouth;

• constipation, decreased urination;

• dizziness, drowsiness, weakness;

• nausea, vomiting;

• headache; or

• feeling restless or nervous.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Using trihexyphenidyl with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Tell your doctor about all your other medicines, especially:

• medicine to treat depression, anxiety, mood disorders, or mental illness;

• cold or allergy medicine (Benadryl and others);

• other medicines to treat Parkinson's disease;

• medicine to treat stomach problems, motion sickness, or irritable bowel syndrome;

• medicine to treat overactive bladder; or

• bronchodilator asthma medication.

This list is not complete. Other drugs may affect trihexyphenidyl, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to trihexyphenidyl.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.