Generic
Trihexyphenidyl Hydrochloride
34 brands available in the market
At a glance
Trihexyphenidyl Hydrochloride is used with other medicines to treat Parkinson's disease and severe movement side effects caused by certain drugs (drug-induced movement disorder).
Description
Trihexyphenidyl HCl is a tertiary amine antimuscarinic which exerts a direct inhibitory effect on the parasympathetic nervous system. It also exhibits a direct spasmolytic action on smooth muscle, weak mydriatic, antisialagogue and cardiovagal blocking effects.
Indications
- Parkinson's disease
- Drug-induced abnormal movements
- Drug-induced extrapyramidal symptoms
Therapeutic class
Antiparkinson drugs
Pharmacological class
Anticholinergic
Pharmacology
Trihexyphenidyl is a non-selective muscarinic acetylcholine receptor antagonist but binds with higher affinity to the M1 subtype. It demonstrates higher affinity for central muscarinic receptors and lower affinity for peripheral ones. It may modify nicotinic acetylcholine receptor neurotransmission, leading to enhanced dopamine release in the striatum.
Mechanism of action
Decreases acetylcholine activity in the brain, improving muscle control and reducing stiffness.
Dosage
Adult Dose (Oral):
- Drug-induced extrapyramidal symptoms: 5-15 mg/day divided every 6-8 hours
- Parkinson disease: Initially 1 mg daily, gradually increased at 3-5 day intervals by 2 mg increments until 6-10 mg daily in 3-4 divided doses; maintenance 5-15 mg/day
- Parkinsonism: 5-15 mg/day divided every 6-8 hours
- Elderly: May require lower doses
Administration
- Take on empty stomach
- Swallow whole; do not chew, crush or break
- Take at the same time each day
- In parkinsonism, before or after meals depends on patient reaction
Missed dose
If you miss a dose, take it as soon as you remember; if almost time for next dose, skip it; do not double the dose.
Side effects
Common Side Effects:
- Dry mouth
- Nausea
- Vomiting
- Constipation
- Blurred vision
- Dizziness
- Upset stomach
- Headache
- Difficulty in urination
- Nervousness
- Tachycardia
- Dilation of pupil
- Increased intraocular pressure
- Confusion
- Memory impairment
Precautions & warnings
- May decrease alertness; do not drive
- Dry mouth may occur; frequent mouth rinses, good oral hygiene, increased water intake, sugarless candy may help
- May cause dry eyes; avoid contact lenses
- Monitoring of intraocular pressure required
- Inform doctor if glaucoma or trouble passing urine
- Do not stop suddenly; may cause NMS
- Caution in hot weather; risk of hyperthermia
Contraindications
- Closed-angle glaucoma
- Chronic pulmonary disease
- Sick sinus syndrome
- Thyrotoxicosis
- Cardiac failure with tachycardia
- Hypersensitivity to trihexyphenidyl
Drug interactions
- Phenothiazines, clozapine, antihistamines, disopyramide, nefopam, amantadine: increased antimuscarinic side effects
- TCAs: synergistic effect
- MAOIs: may cause dry mouth, blurred vision, urinary hesitancy or retention, constipation
- Metoclopramide and domperidone: may antagonise effect on GI function
- Levodopa: reduced absorption
- Parasympathomimetics: may antagonise effect
- Cannabinoids, barbiturates, opiates, alcohol: additive effects, abuse potential
Food interactions
May cause excessive drowsiness with alcohol.
Use in pregnancy
Use in Pregnancy: May be unsafe; animal studies show harmful effects; consult your doctor.
Pregnancy Category: C — always consult a doctor before taking during pregnancy.
Use in lactation
Use in Lactation: Probably safe; limited human data suggests no significant risk; consult your doctor.
Pediatric use
Safety and efficacy not established in pediatric patients
Geriatric use
Initial dose should be low and increased gradually, especially in patients over 60 years
Renal / hepatic impairment
Renal Impairment: Limited information; close monitoring required in kidney disease
Hepatic Impairment: Limited information; consult your doctor
Overdose effects
Symptoms: Central anticholinergic syndrome (delirium, hallucinations, tachycardia, dry skin, urinary retention, seizures, coma).
Treatment: Gastric lavage, supportive; diazepam or short-acting barbiturate; phenothiazines contraindicated.
Storage conditions
Store at temperature not exceeding 30°C in a dry place. Protect from light.