What are the considerations when prescribing Artane (Trihexyphenidyl)?

Considerations When Prescribing Artane (Trihexyphenidyl)

Trihexyphenidyl should be avoided in patients with extrapyramidal symptoms caused by typical antipsychotics, as it may increase the risk of tardive dyskinesia. 1

Indications

• Indicated as an adjunct in treating all forms of parkinsonism (postencephalitic, arteriosclerotic, and idiopathic) 2
• Used as adjuvant therapy when treating parkinsonism with levodopa 2
• Indicated for control of extrapyramidal disorders caused by central nervous system drugs (dibenzoxazepines, phenothiazines, thioxanthenes, and butyrophenones) 2
• Effective in treating dystonia (37% improvement rate) with better response in tonic torticollis (80%) than clonic variant (22%) 3
• Shows efficacy in rhythmic-oscillatory movements of brainstem-cerebellar origin (90% response) and cerebellar tremor (75% response) 3

Contraindications

• Avoid in patients with narrow-angle glaucoma 2
• Patients should have gonioscope evaluation prior to starting therapy 2
• Not recommended for prophylactic administration during neuroleptic therapy 2
• Use with caution in pregnant women as teratogenic effects are unknown 2
• Use with caution in nursing mothers as it may suppress lactation 2

Dosing Considerations

• Initial dosing should be low, particularly in elderly patients 2
• Dosage should be decreased in hot weather to prevent anhidrosis and hyperthermia 2
• Dosage may need to be reduced when used concomitantly with levodopa 2
• In movement disorders, initial total daily dose of 2 mg can be gradually increased up to 60 mg over 4-6 weeks 3

Adverse Effects

• May cause cognitive dysfunction in the elderly, including confusion and memory impairment 2
• Can impair mental and physical abilities required for operating machinery or driving 2
• May increase intraocular pressure; close monitoring required 2
• Can cause anhidrosis and hyperthermia, especially in hot weather 2
• Abrupt withdrawal may result in acute exacerbation of parkinsonism symptoms 2
• Common side effects include dry mouth, jitteriness, stomatitis, blurred vision, and forgetfulness 3
• Decreases regional cerebral blood flow and oxygen metabolism by 10-15% in the striatum and cortical areas 4

Drug Interactions

• Cannabinoids, barbiturates, opiates, and alcohol may have additive effects, creating abuse potential 2
• Concurrent use with alcohol or other CNS depressants increases sedative effects 2
• MAOIs and tricyclic antidepressants with anticholinergic activity may intensify anticholinergic effects 2
• Increased risk for tardive dyskinesia during concomitant administration with neuroleptics 2

Special Populations

• Safety and effectiveness in pediatric patients have not been established 2
• Elderly patients (over 60) have increased sensitivity to parasympatholytic drugs; start with low doses 2
• Use with caution in chronically ill patients, alcoholics, and those with central nervous system disease 2
• Use with caution in those who perform manual labor in hot environments 2

Monitoring

• Close monitoring of intraocular pressure is necessary 2
• Monitor for signs of anhidrosis and hyperthermia 2
• Watch for symptoms of Neuroleptic Malignant Syndrome with dose reduction or discontinuation 2
• Be alert for potential abuse, particularly when used with other substances 5

Important Warnings

• Blindness has been reported due to aggravation of narrow-angle glaucoma 2
• Severe anhidrosis and fatal hyperthermia have occurred with anticholinergics 2
• Potential for abuse exists, especially in polydrug users seeking mental alterations 5
• May be associated with Neuroleptic Malignant Syndrome upon dose reduction or discontinuation 2