Trihexyphenidyl
ARTANE
What it isCentral antimuscarinic; drug-induced parkinsonism, dystonia and tremor.
Why this oneIt is effective for dystonia, including the primary dystonias, where few oral agents work.
What limits itAnticholinergic burden and cognitive impairment, so it is poor in the elderly. It does not help tardive dyskinesia and can worsen it.
FDA-approved for
- Parkinson disease / drug-induced EPS (1949)
Off-label
- primary dystonia
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Idiopathic parkinsonism | Adults | 1 mg on day 1 | 6–10 mg/day | 12–15 mg/day (postencephalitic) |
| Drug-induced extrapyramidal reactions | Adults | 1 mg | 5–15 mg/day | 15 mg/day |
Titration Increase by 2 mg increments every 3 to 5 days (parkinsonism)
Renal Undefined
Hepatic Undefined
Instructions
- Individualize; start low, especially in patients over 60 years
- Give before or after meals per patient tolerance
- Divide daily dose into 3 (at mealtimes); doses >10 mg/day into 4 (add a bedtime dose)
- With levodopa, reduce the dose of each (usually 3–6 mg/day trihexyphenidyl)
Cautions
- Anticholinergic effects (dry mouth, blurred vision, urinary retention, tachycardia, mydriasis)
- Angle-closure glaucoma reported with long-term use
- Mental confusion, agitation, hallucinations — especially with arteriosclerosis or in the elderly
- Constipation, dilation of colon, paralytic ileus
- Potential for abuse (euphoria) with overdosage
- Suppurative parotitis from excessive dry mouth
Adverse reactions
- Dry mouth
- Blurred vision
- Dizziness
- Mild nausea
- Nervousness
- Constipation
- Drowsiness
- Urinary hesitancy/retention
- Tachycardia
Pregnancy Undefined
Lactation Undefined
NO BOXED WARNINGS
Principal riskAnticholinergic burden and cognitive impairment
Cost, est. cash$5–$150/month
Generic entry1982
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.
Mechanism of action: Trihexyphenidyl ballicule
Open Trihexyphenidyl in the interactive console ↗
Memory aids: mascots and interaction avatars
“mad as a hatter” → BBB-crossing antimuscarinic
