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Trihexyphenidyl Dosage

Medically reviewed by Last updated on Feb 8, 2023.

Applies to the following strengths: 2 mg; 5 mg; 2 mg/5 mL

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


  • 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

  • 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.

Renal Dose Adjustments

Use with caution due to a lack of pharmacokinetic data; start low, titrate conservatively and closely monitor

Liver Dose Adjustments

Use with caution due to a lack of pharmacokinetic data; start low, titrate conservatively and closely monitor

Dose Adjustments

Elderly: Patients over 60 years have shown greater sensitivity to the action of parasympatholytic drugs; therefore, initial doses should be low and patients should be monitored closely


  • Abrupt discontinuation should be avoided as it may result in acute exacerbation of parkinsonism symptoms
  • Neuroleptic malignant syndrome has been associated with abrupt withdrawal

Concomitant Use with Other Parasympathetic Inhibitors:
  • This drug may be substituted for other parasympathetic inhibitors
  • To substitute, initiate with partial substitution, then progressively reduce the other parasympathetic inhibitor as the dose of this drug is increased



  • Hypersensitivity to the active drug or any product excipients
  • Narrow angle glaucoma

Safety and efficacy have not been established in patients younger than 18 years.

Consult WARNINGS section for additional precautions.


Data not available

Other Comments

Administration advice:

  • Take orally with or without food
  • If gastrointestinal upset occurs, take with food

Storage requirements:
  • Oral Solution: Protect from light and moisture; do not freeze

  • Anticholinergics, including this drug, are not effective in controlling tardive dyskinesia (TD) and in some cases, may aggravate it or induce previously suppressed symptoms.
  • This drug has been abused because of its hallucinogenic and euphorigenic effects; the precise mechanism for the euphoria and hallucinations are unclear, but it is possible that the drug produces a form of anticholinergic delirium.

  • Check intraocular pressures at regular intervals

Patient advice:
  • Read the US FDA-approved patient labeling.
  • Patients should be cautioned about use in hot weather; lack of sweating may cause hyperthermia/heat-stroke.
  • This drug may cause drowsiness; avoid driving or operating machinery if you feel drowsy or dizzy.
  • Patients should be counseled on concurrent use of alcohol and CNS depressants.
  • Patients should be instructed to report gastrointestinal problems, fever, or vision problems.
  • Patients should be advised not to stop taking this drug without consulting with their healthcare provider.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.