Trihexyphenidyl Dosage

Medically reviewed by Drugs.com. Last updated on Feb 10, 2025.

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.

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

Discontinuation:

• 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

Precautions

CONTRAINDICATIONS:

• 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.

Dialysis

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

General:

• 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.

Monitoring:

• 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.

See also:

Further information

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

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