Trihexyphenidyl is used to treat the symptoms of Parkinson's disease and tremors caused by other medical problems or drugs.
This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
Trihexyphenidyl comes as a tablet, liquid, and extended-release (long-acting) capsule to take by mouth. It usually is taken three or four times a day (with meals and at bedtime). The controlled-release capsules are taken once a day (after breakfast) or twice a day, every 12 hours. You may have to take trihexyphenidyl for a long time to treat Parkinson's disease. However, trihexyphenidyl may only be needed for a short period to treat other conditions. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take trihexyphenidyl exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Do not stop taking trihexyphenidyl suddenly without talking with your doctor, especially if you are also taking other medications. Sudden stoppage can cause symptoms of Parkinson's disease to return.
Do not open the extended-release capsules and do not chew the tablets. Swallow them whole.
Before taking trihexyphenidyl,
- tell your doctor and pharmacist if you are allergic to trihexyphenidyl or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially amantadine (Symmetrel), digoxin, haloperidol (Haldol), levodopa (Larodopa, Sinemet), tranquilizers, and vitamins.
- tell your doctor if you have or have ever had kidney or liver disease, myasthenia gravis, heart or blood pressure problems, problems with your urinary system or prostate, or stomach problems.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking trihexyphenidyl, call your doctor.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking trihexyphenidyl.
- you should know that this drug may make you drowsy. Do not drive a car or operate machinery until you know how this drug affects you.
- remember that alcohol can add to the drowsiness caused by this drug.
Trihexyphenidyl may cause an upset stomach. Take trihexyphenidyl with food or milk.
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
Trihexyphenidyl may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- dizziness or blurred vision
- dry mouth
- upset stomach
- increased eye sensitivity to light
- difficulty urinating
If you experience any of the following symptoms, call your doctor immediately:
- skin rash
- fast, irregular, or pounding heartbeat
- delusions or hallucinations
- eye pain
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at Web Site] or by phone [1-800-332-1088].
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). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
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.
¶This branded product is no longer on the market. Generic alternatives may be available.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Last Reviewed: October 1, 2010.