Trihexyphenidyl
ARTANE
Pronunciation: trye-hex-ee-FEN-i-dil
“Triangle-hexagon Art thing”
“mad as a hatter” → BBB-crossing antimuscarinic
What it isCentral antimuscarinic; drug-induced parkinsonism, dystonia and tremor.
Why this oneEffective 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.
Trihexyphenidyl prescription history
Animated chart of estimated U.S. prescriptions per year, Parkinson medicines (1948–2026). Trihexyphenidyl enters in 1949 (estimated).
FDA-approved for
- Parkinson disease / drug-induced EPS (1949)
Off-label
- primary dystonia
Principal riskAnticholinergic burden and cognitive impairment
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.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Parkinsonism, all forms (adjunct; idiopathic regimen) | Adult | 1 mg on day 1 | 6–10 mg/day divided TID with meals | 12–15 mg/day (chiefly postencephalitic) |
| Parkinsonism — adjunct to levodopa | Adult | Reduce usual dose of each drug | 3–6 mg/day in divided doses | Undefined |
| Drug-induced extrapyramidal disorders (phenothiazines, thioxanthenes, butyrophenones, dibenzoxazepines) | Adult | 1 mg single dose | 5–15 mg/day (some controlled on 1 mg/day) | 15 mg/day (top of usual range) |
Titration Idiopathic parkinsonism: ↑2 mg every 3–5 days; drug-induced EPS: ↑ progressively if not controlled within a few hours
Renal Undefined
Hepatic Undefined
Instructions
- Divide daily dose TID at mealtimes; >10 mg/day may be split QID (3 with meals + 1 at bedtime)
- Take before or after meals per response (before if excessive dry mouth unless nausea; after if sialorrhea)
- Start low and increase gradually, especially age >60
- Avoid abrupt withdrawal (parkinsonism exacerbation, NMS) — reduce gradually
Available strengths
- tab 2, 5 mg
- sol 2 mg/5 mL
Contraindications
- Narrow-angle glaucoma (blindness reported with long-term use)
Cautions
- Angle-closure glaucoma — gonioscopy before starting; monitor IOP
- Hot weather/anhidrosis — fatal hyperthermia (esp. with other atropine-like drugs, chronic illness, alcoholism, CNS disease, manual labor in heat)
- Neuroleptic malignant syndrome with dose reduction or discontinuation
Adverse reactions
- Dry mouth (30–50% minor effects)
- Blurred vision
- Dizziness
- Mild nausea
- Nervousness
- Confusion/memory impairment
- Constipation
- Drowsiness
- Urinary hesitancy/retention
- Tachycardia
- Mydriasis/increased IOP
Pregnancy Pregnancy Category C; no animal or human data — use only if clearly needed.
Lactation Unknown if excreted in milk; may suppress lactation — use only if benefit outweighs infant risk.
Cost
Generic entry1982
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Memory aids: interaction avatars
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Self-check
- Which movement disorder can trihexyphenidyl treat even in primary forms?
Dystonia. - Does trihexyphenidyl help tardive dyskinesia?
No; it can worsen it.