What is the recommended dosage of Trihexyphenidyl (Artane)?

Trihexyphenidyl Dosage Recommendations

For idiopathic Parkinsonism, start with 1 mg on day one, then increase by 2 mg every 3-5 days until reaching 6-10 mg daily in divided doses, with some patients requiring up to 12-15 mg daily; for drug-induced parkinsonism, the typical range is 5-15 mg daily, though control may be achieved with as little as 1 mg daily. 1

Initial Dosing Strategy

Idiopathic Parkinsonism

• Begin with 1 mg on the first day 1
• Increase by 2 mg increments at intervals of 3-5 days 1
• Target dose: 6-10 mg total daily dose for most patients 1
• Postencephalitic patients may require 12-15 mg daily 1

Drug-Induced Parkinsonism (Extrapyramidal Symptoms)

• Start with a single 1 mg dose 1
• If symptoms not controlled within a few hours, progressively increase subsequent doses 1
• Typical effective range: 5-15 mg daily, though some patients respond to as little as 1 mg daily 1
• Consider temporarily reducing the tranquilizer dose when initiating trihexyphenidyl, then adjust both medications 1

Concomitant Use with Levodopa

• Usual effective dose: 3-6 mg daily in divided doses when used with levodopa 1
• Both medications may need dose reduction when used together 1

Administration Guidelines

Timing and Frequency

• Divide total daily intake into 3 doses taken at mealtimes 1
• For doses >10 mg daily, divide into 4 parts: 3 at mealtimes and 1 at bedtime 1
• Postencephalitic patients with excessive salivation may prefer taking doses after meals 1
• If excessive dry mouth occurs, consider taking before meals (unless nausea develops) 1

Special Population Considerations

Elderly Patients (>60 years)

• Start with lower initial doses and increase more gradually 1
• The American Academy of Family Physicians recommends avoiding anticholinergics like trihexyphenidyl in patients with cognitive impairment when possible 2
• Do not use benztropine or trihexyphenidyl to treat extrapyramidal symptoms in elderly patients with dementia on typical antipsychotics 2

Dose Titration for Specific Movement Disorders

Research evidence demonstrates varying responses across movement disorder subtypes:

Dystonia

• Studies used gradual titration from 2 mg daily up to 60 mg daily over 4-6 weeks 3
• A prospective double-blind trial found 30 mg daily was generally well tolerated in torsion dystonia, with 71% showing clinically significant response 4
• Tonic torticollis responds better than clonic variant (80% vs 22% response rate) 3

Other Movement Disorders

• Rhythmic-oscillatory movements of brainstem-cerebellar origin showed 90% response 3
• Cerebellar tremor showed 75% response 3

Critical Safety Warnings

Withdrawal Precautions

• Never abruptly withdraw trihexyphenidyl - may cause acute exacerbation of parkinsonian symptoms 1
• Abrupt withdrawal may result in neuroleptic malignant syndrome (NMS) 1

Abuse Potential

• Case reports document abuse potential, with one patient using up to 200 mg daily for euphoric effects 5
• Clinicians should be alert when prescribing to patients with abuse potential 5
• High doses may precipitate anticholinergic toxic psychosis and interfere with antipsychotic absorption 5

Common Pitfalls to Avoid

• Avoid use in cognitively impaired patients when possible, as anticholinergics can worsen mental status 2
• Do not use to treat extrapyramidal symptoms in elderly dementia patients on antipsychotics 2
• Monitor for anticholinergic side effects: dry mouth, blurred vision, jitteriness, stomatitis, and forgetfulness 3
• Manage dry mouth with mint candies, chewing gum, or water 1