Potassium Chloride
Severe
Database
Clinical effect not specified
Source: DDInter
Drug reference
Trihexyphenidyl
Anticholinergic (centrally-acting) / antimuscarinic · Antiparkinsonian
Also known as Benzhexol, Artane
START
1 mg OD; increase gradually; use lowest effective dose; avoid in elderly if possible; check for glaucoma, urinary retention, constipation before starting
TYPICAL MAX
15 mg/day
STOP IF
Severe confusion, urinary retention, signs of anticholinergic toxicity, narrow-angle glaucoma symptoms
WATCH
Cognitive function (especially elderly), urinary output, constipation, intraocular pressure (if at risk), signs of anticholinergic toxicity
CDSCO approvedSchedule HJan AushadhiATC N04AA01
KDIGO 2024 + manufacturer label
- ONSET
- 1.5h · 1-2 hours
- PEAK
- 2.5h · 2-3 hours
- t½
- 3.7h · 3.3-4.1 hours
- DURATION
- 8h · 6-12 hours
EXCRETION
Renal
route + CYP
INTERACTIONS
5 major
SEVERE in our sources
PREGNANCY
Use only if clearly needed; limited data
FDA category + note
Top interactionssee all 9 →
- Potassium ChlorideSevereDatabaseDDInter
- Potassium CitrateSevereDatabaseDDInter
- TopiramateSevereDatabaseDDInter
- Other AnticholinergicsSevereDatabaseKimi deep-research + Cla
Available in India
109 branded formulations and 93 fixed-dose combinations. Look up specific brands in the Drugs workspace.
Jan Aushadhi — generic available at GoI pharmacies
Mechanism
Competitive antagonist at central muscarinic acetylcholine receptors (M1), restoring the balance between dopaminergic and cholinergic neurotransmission in the basal ganglia. Reduces relative cholinergic excess that occurs when dopaminergic tone is decreased (Parkinson's) or when D2 receptors are blocked (drug-induced EPS).
Indications
Parkinson's disease (adjunct to levodopa)Drug-induced extrapyramidal symptoms (EPS) from antipsychoticsDystonia (acute and tardive)Tremor-predominant Parkinson's (monotherapy in early disease)
Dosing
- Adult
- Parkinson's: start 1 mg OD, increase by 2 mg every 3-5 days; usual 6-10 mg/day in 3 divided doses; max 15 mg/day. EPS: 1 mg OD-TDS; max 5-15 mg/day
- Pediatric
- Not recommended in children
- Renal adjustment
- Use with caution; reduced clearance
- Hepatic adjustment
- Use with caution
- Geriatric
- Start 0.5-1 mg; increased risk of anticholinergic toxicity (confusion, falls, urinary retention, constipation); avoid if possible
- Max dose
- 15 mg/day
Pharmacokinetics
Onset
1-2 hours (anticholinergic effect)
Peak effect
2-3 hours (Tmax)
Duration
6-12 hours
Half-life
3.3-4.1 hours
Bioavailability
Well absorbed orally
Protein binding
Not well characterized
Metabolism
Hepatic; not well characterized
Excretion
Renal
Contraindications
- Narrow-angle glaucoma
- Urinary retention / bladder neck obstruction
- GI obstruction (pyloric or duodenal stenosis)
- Myasthenia gravis
- Megacolon / toxic megacolon
- Severe ulcerative colitis
- Hypersensitivity to trihexyphenidyl
Side effects
Common
Dry mouthBlurred visionConstipationUrinary retentionTachycardiaDizzinessConfusion (especially elderly)SedationNausea
Serious
- Acute anticholinergic syndrome (hyperthermia, delirium, tachycardia, seizures)
- Narrow-angle glaucoma precipitation
- Paralytic ileus
- Heat stroke (impaired thermoregulation)
- Psychosis / hallucinations
- Severe confusion / delirium
Pregnancy & lactation
Pregnancy
Use only if clearly needed; limited data
Lactation
Excretion in breast milk unknown; may suppress lactation; use with caution
Drug interactions
Potassium Citrate
Severe
Database
Clinical effect not specified
Source: DDInter
Topiramate
Severe
Database
.
Source: DDInter
Other Anticholinergics
Severe
Database
Additive anticholinergic toxicity; high risk of confusion, constipation, urinary retention, heat stroke
Avoid multiple anticholinergics; monitor for anticholinergic toxicity
Source: Kimi deep-research + Cla
Zonisamide
Severe
Database
Clinical effect not specified
Source: DDInter
Digoxin
Moderate
Database
Increased risk of digoxin toxicity (e.g., nausea, vomiting, arrhythmias, visual disturbances).
Monitor digoxin serum concentrations closely when initiating or discontinuing trihexyphenidyl. Adjust digoxin dose as needed. Monitor for signs and symptoms of digoxin toxicity.
Source: DDInter
Metoclopramide
Moderate
Database
Reduced efficacy of metoclopramide in promoting gastrointestinal motility. May worsen extrapyramidal symptoms if metoclopramide is used for its antiemetic effects.
Avoid concomitant use if possible. If both are necessary, monitor for reduced efficacy of metoclopramide. Consider alternative antiemetics or prokinetics if appropriate.
Source: DDInter
Cholinesterase Inhibitors
Moderate
Database
Pharmacologic antagonism; cholinesterase inhibitors increase acetylcholine while trihexyphenidyl blocks muscarinic receptors
Avoid concurrent use if possible; monitor cognition
Source: Kimi deep-research + Cla
Phenothiazines
Moderate
Database
Additive anticholinergic effects; phenothiazines have intrinsic anticholinergic activity
Monitor for anticholinergic toxicity
Source: Kimi deep-research + Cla
3 additional unreviewed or low-confidence interactions hidden because their provenance or source detail is insufficient.
Related guidelines
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OTHER · Gastroenterology · 2016
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OTHER · Gastroenterology · 2015
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KDIGO · Nephrology · 2024
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ISG · Gastroenterology · 2022
Ask House about Trihexyphenidyl
Continue into a citation-backed clinical answer with the drug context already attached.
Textbook-sourced·Sources: KD Tripathi 7e, Goodman & Gilman 14e, Katzung, BNF·Updated: 2026-05-19·Cockpit curated: 2026-05-19