1. Trihexyphenidyl oral tablet is only available as a generic drug. It doesn’t have a brand-name version.
  2. Trihexyphenidyl comes in two forms: an oral solution and an oral tablet.
  3. Trihexyphenidyl oral tablet is used to treat all forms of parkinsonism, including Parkinson’s disease. It’s also used to treat severe movement side effects caused by antipsychotic drugs.

  • Heat stroke warning: Taking trihexyphenidyl can put you at risk of heat stroke. It makes you sweat less, which can make your body less able to cool itself. This increases your risk of hyperthermia (very high body temperature). If your body gets too hot and cannot cool down, you could have heat stroke.
  • Neuroleptic malignant syndrome warning: Suddenly stopping or reducing your dose of trihexyphenidyl too quickly increases your risk of this rare but life-threatening condition. If you have any of the following symptoms while taking this drug, call your doctor immediately: high fever, muscle stiffness, slowed thoughts, changes in blood pressure, fast heart rate, or sweating.
  • Dementia warning: Research has indicated that this type of medication, which is called an anticholinergic, can raise your risk of dementia.

Trihexyphenidyl is a prescription drug. It comes as an oral solution and an oral tablet.

Trihexyphenidyl oral tablet is only available as a generic drug. It doesn’t have a brand-name version.

Trihexyphenidyl may be used as part of a combination therapy. This means you may need to take it with other medications.

Why it’s used

Trihexyphenidyl oral tablet is used to treat all forms of parkinsonism, including Parkinson’s disease. It’s also used to treat severe movement side effects caused by antipsychotic drugs.

How it works

Trihexyphenidyl belongs to a class of drugs called anticholinergics. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Trihexyphenidyl works by blocking the function of a certain part of your nervous system that regulates body movements. It helps relax certain muscles and makes it easier to move freely.

Trihexyphenidyl oral tablet may cause drowsiness. It can also cause other side effects.

More common side effects

Some of the more common side effects that can occur with use of trihexyphenidyl include:

  • dry mouth
  • blurred vision
  • dizziness
  • nausea
  • nervousness
  • constipation
  • drowsiness
  • trouble urinating

In addition to the side effects listed above, the following have been reported in children who have used this drug:

  • forgetfulness
  • weight loss
  • restlessness
  • trouble sleeping
  • muscle spasms
  • involuntary body movements

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Irregular heartbeats
  • Hallucinations
  • Paranoia
  • Glaucoma. Symptoms can include:
    • eye pain
    • blurred vision
    • sudden or gradual loss of vision
    • tunnel vision
    • rainbow-colored circles around bright lights
  • Intestinal problems. Symptoms can include:
    • bloating
    • stomach pain
    • severe constipation
    • nausea
    • vomiting
    • loss of appetite
  • Heat stroke or trouble sweating or both. Symptoms can include:
    • inability to sweat
    • tiredness
    • fainting
    • dizziness
    • muscle or stomach cramps
    • nausea
    • vomiting
    • diarrhea
    • confusion
    • fever
  • Neuroleptic malignant syndrome (NMS). Symptoms include:
    • fever
    • rigid muscles
    • involuntary movements
    • mental status changes
    • fast pulse
    • fast and shallow breathing
    • high or low blood pressure

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Trihexyphenidyl oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with trihexyphenidyl are listed below.

Drug used for Parkinson’s disease

Taking levodopa and trihexyphenidyl together may cause an increase in drug-induced involuntary movement. When taken together, the doses of one or the other of these drugs may need to be reduced.

Depression drugs

When taken with trihexyphenidyl, certain depression drugs can increase the risk of side effects such as dry mouth, trouble urinating, bloating, less sweat, and increased body temperature. Examples of these drugs include:

  • isocarboxazid
  • phenelzine
  • tranylcypromine
  • amitriptyline
  • clomipramine
  • desipramine
  • nortriptyline

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

Do not stop taking trihexyphenidyl abruptly Your symptoms may return quickly and you may develop a life-threatening condition called neuroleptic malignant syndrome. Be sure to talk to your doctor before stopping this drug.

This drug comes with several warnings.

Alcohol interaction warning

If you drink alcohol, talk to your doctor. Consuming drinks that contain alcohol can increase your risk of drowsiness from trihexyphenidyl.

Warnings for people with certain health conditions

For people with open-angle glaucoma: You should not use trihexyphenidyl if you have open-angle glaucoma because it may cause blindness. Your doctor should do an eye exam before starting you on this drug to make sure your eye sight is okay.

For people with liver disease: If you have liver disease, your body may not be able to process this drug well. This can cause an increase in the levels of this drug in your body. This can raise your risk of side effects.

For people with heart disease: If you have heart disease, you may be at an increased risk for angina (chest pain) or tachycardia (a fast heart rate). Your doctor may want to monitor you more closely for side effects and start you on a lowered dosage to see how you respond.

For people with kidney disease: If you have kidney problems or a history of kidney disease, you may not be able to clear this drug from your body well. This may increase the levels of this drug in your body and cause more side effects. Your doctor may monitor you more closely for side effects.

For people with high blood pressure: You may be at increased risk for angina (chest pain), a heart attack, or tachycardia (a fast heart rate). Your doctor may monitor you more closely for side effects and start you on a lower dosage to see how you respond.

For people with arteriosclerosis: If you have hardening of the walls of your arteries, your sensitivity to this drug may be increased. This can cause mental confusion, irritability, behavior changes, nausea, and vomiting. To avoid these symptoms, your doctor may start you at a low dosage and slowly increase it.

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Drug form and strengths

Generic: Trihexyphenidyl

  • Form: oral tablet
  • Strengths: 2 mg, 5 mg

Dosage for parkinsonism

Adult dosage (ages 18–59 years)

  • Typical starting dosage: 1 mg per day.
  • Dosage increases: Your doctor may increase your dosage by 2 mg every 3–5 days, until you’re taking 6–10 mg per day.
  • Note: If your parkinsonism was caused by a viral infection, you may need a dosage of 12–15 mg per day.

Child dosage (ages 0–17 years)

It has not been confirmed that trihexyphenidyl is safe and effective for use in children younger than 18 years.

Senior dosage (ages 65 years and older)

If you’re older than 60 years, you may be more sensitive to the effects of trihexyphenidyl. It has been shown to cause more confusion and memory loss in older people. Your doctor may start you on a low dosage and watch for side effects.

Dosage for drug-induced movement disorders

Adult dosage (ages 18–59 years)

  • Typical starting dosage: 1 mg per day as a single dose.
  • Dosage increases: If the movements are not controlled in a few hours, your doctor may increase your doses that follow until your symptoms disappear.
  • Typical maintenance dosage: This can range between 5 mg and 15 mg per day. It will be determined by how well your symptoms are controlled.
  • Note: Your doctor may be able to control your symptoms better while you take trihexyphenidyl if your dosage of the medication causing the symptoms is reduced.

Child dosage (ages 0–17 years)

It has not been confirmed that trihexyphenidyl is safe and effective for use in children younger than 18 years.

Senior dosage (ages 65 years and older)

If you’re older than 60 years, you may be more sensitive to the effects of trihexyphenidyl. It has been shown to cause more confusion and memory loss in older people. Your doctor may start you on a low dosage and watch for side effects.

Dosage warnings

  • Your doctor should always start you on a low dosage of trihexyphenidyl and slowly increase your dosage as needed, especially if you’re aged 60 years or older. Increasing the dosage slowly will lower your risk of side effects.
  • Do not stop taking trihexyphenidyl abruptly. You can have a quick return of your symptoms and possibly develop a life-threatening condition called neuroleptic malignant syndrome.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

Trihexyphenidyl oral tablet is used for both long-term and short-term treatment. It’s used for long-term treatment of Parkinson’s disease. It may be used for both long-term and short-term treatment of other forms of parkinsonism or for drug-induced movement disorders.

This drug comes with risks if you don’t take it as prescribed.

If you stop taking the drug or don’t take it at all: Do not stop taking trihexyphenidyl abruptly. You can have a quick return of your symptoms and possibly develop a life-threatening condition. This condition is called neuroleptic malignant syndrome. If you don’t take this drug at all, your symptoms will continue or worsen.

If you miss doses or don’t take the drug on schedule: If you miss several doses or don’t take this medication on the schedule recommended by your doctor, your symptoms can return quickly.

If you take too much: You could have dangerous levels of the drug in your body. Symptoms of an overdose of this drug can include:

  • dilated pupils
  • dry skin
  • fever
  • fast heart rate
  • trouble urinating
  • bloating
  • bad breath
  • confusion
  • hallucinations

If you think you’ve taken too much of this drug, call your doctor or seek guidance from the American Association of Poison Control Centers at 800-222-1222 or through their online tool. But if your symptoms are severe, call 911 or go to the nearest emergency room right away.

What to do if you miss a dose: Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working: Your symptoms should improve.

Keep these considerations in mind if your doctor prescribes trihexyphenidyl for you.

General

  • You can cut or crush the tablet.
  • Taking this drug with food may help to reduce upset stomach. You may wish to divide your daily dose into thirds and take each third with a meal. If your dose is more than 10 mg per day, you can divide it into fourths. You can take three of the fourths with your meals, and the last fourth at bedtime.

Storage

  • Store trihexyphenidyl at room temperature between 68°F and 77°F (20°C and 25°C).
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t harm your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

During your treatment with this drug, your doctor will check to make sure your symptoms don’t return and your vision isn’t changing. Your doctor may also run tests to check the function of your liver and kidneys.

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.