Home Drug Guide Trihexyphenidyl Hydrochloride

Drug Guide

Generic Name

Trihexyphenidyl Hydrochloride

Brand Names Artane, Tremin

Classification

Therapeutic: Antiparkinsonian agent

Pharmacological: Anticholinergic

FDA Approved Indications

Parkinson's disease
Drug-induced extrapyramidal symptoms

Mechanism of Action

Trihexyphenidyl is an anticholinergic that blocks cholinergic activity in the central nervous system, thereby helping to restore the balance between dopamine and acetylcholine, which is disturbed in Parkinson's disease.

Dosage and Administration

Adult: Typically 1-2 mg 3-4 times daily; dosage may be adjusted based on response and tolerability.

Pediatric: Not generally recommended for pediatric use.

Geriatric: Start at lower doses due to increased risk of adverse effects; usual starting dose is 1 mg twice daily, titrate as needed.

Renal Impairment: Use with caution; dosage adjustment may be necessary.

Hepatic Impairment: Use with caution; monitor for increased effects and adverse reactions.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Widely distributed including CNS; crosses the blood-brain barrier.

Metabolism: Partially metabolized in the liver.

Excretion: Excreted primarily via the kidneys.

Half Life: Approximately 3-4 hours.

Contraindications

Glaucoma (especially narrow-angle glaucoma)
Gastrointestinal or urinary tract obstruction
Prostatic hypertrophy

Precautions

Use with caution in patients with cardiac arrhythmias, myasthenia gravis, or elderly patients due to risk of cognitive impairment and adverse effects.

Adverse Reactions - Common

Dry mouth (Common)
Blurred vision (Common)
Constipation (Common)
Dizziness (Common)

Adverse Reactions - Serious

Confusion or hallucinations (Uncommon in elderly)
Urinary retention (Uncommon)
tachycardia or other cardiac arrhythmias (Rare)

Drug-Drug Interactions

Other anticholinergics (risk of additive effects)
CNS depressants (enhanced sedation)
NSAIDs (potential increased GI irritation)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for dry mouth, blurred vision, urinary retention, constipation, mental status changes, and cardiac symptoms.

Diagnoses:

Risk for falls due to dizziness or blurred vision
Impaired urinary elimination
Risk for constipation

Implementation: Administer with food if GI upset occurs; advise patients to change positions slowly; monitor urinary output and bowel habits.

Evaluation: Assess symptom relief and monitor for adverse effects; adjust dose accordingly.

Patient/Family Teaching

Advise patients to avoid alcohol and CNS depressants.
Educate about dry mouth relief strategies.
Encourage adequate hydration and fiber intake.
Warn about potential for drowsiness or dizziness and advise caution when driving or operating machinery.

Special Considerations

Black Box Warnings:

Use with caution in elderly patients due to increased risk of cognitive impairment, hallucinations, and confusion.

Genetic Factors: N/A

Lab Test Interference: N/A

Overdose Management

Signs/Symptoms: Dry mouth, blurred vision, urinary retention, hot and dry skin, hallucinations, tachycardia.

Treatment: Supportive care; symptomatic treatment; gastric lavage if recent ingestion; physostigmine may be used as an antidote in severe cases.

Storage and Handling

Storage: Store at room temperature, away from moisture, light, and humidity.

Stability: Stable under recommended storage conditions.