Indications
Trihexy tablet is indicated as an adjunct in the treatment of all forms of parkinsonism (post-encephalitic, arteriosclerotic, and idiopathic). It is also useful with levodopa therapy. Additionally, it is used to control extrapyramidal disorders caused by CNS drugs such as dibenzoxazepines, phenothiazines, thioxanthenes, and butyrophenones.

Description
Trihexy works by inhibiting the parasympathetic nervous system. It also relaxes smooth muscles both directly and indirectly.

Pharmacology
Trihexyphenidyl is a non-selective muscarinic receptor antagonist with higher affinity for M1 receptors in the brain. It may enhance dopamine release in the brain, helping to reduce Parkinson’s symptoms.

Dosage & Administration
Dosage should be individualized. Start with a low dose and increase gradually.
Idiopathic Parkinsonism: Start with 1 mg daily, increase gradually up to 6–10 mg/day (sometimes 12–15 mg).
Drug-induced Parkinsonism: mg/day depending on response.
Divide total daily dose into 3–4 doses. Avoid abrupt withdrawal.

Use in Children
Safety and effectiveness are not established.

Interaction
Alcohol, CNS depressants, barbiturates, opioids may increase sedative effects.
MAO inhibitors and tricyclic antidepressants may increase anticholinergic effects.
Levodopa dose may need adjustment.

Contraindications
Hypersensitivity to Trihexyphenidyl
Narrow-angle glaucoma

Side Effects
Common: Dry mouth, blurred vision, dizziness, nausea, nervousness
Serious: Confusion, hallucinations, constipation, urinary retention, tachycardia

Pregnancy & Lactation
Use only if benefit outweighs risk. Caution in breastfeeding.

Precautions & Warnings
Monitor intraocular pressure
Risk of glaucoma
Use cautiously in hot weather (risk of heatstroke)
Abrupt withdrawal may cause Neuroleptic Malignant Syndrome (NMS)

Overdose Effects
Symptoms: Delirium, confusion, hallucination, tachycardia, dry skin
Treatment: Supportive care, gastric lavage, diazepam if needed

Therapeutic Class
Antiparkinson drugs