Pronunciation: try-hex-ee-FEN-in-dill HIGH-droe-KLOR-ide
- Tablets 2 mg
- Tablets 5 mg
- Elixir 2 mg/5 mL
- Capsules, sustained-release 5 mg
- Tablets 2 mg
- Tablets 5 mg
Exerts direct inhibitory effect on parasympathetic nervous system by inhibiting actions of acetylcholine; has relaxing effect on smooth musculature.
T max is 1 to 1.3 h, C max is 87.2 mcg/L, and oral bioavailability is approximately 100%. Trihexyphenidyl is tolerated best in divided doses and taken at mealtimes.
Trihexyphenidyl t ½ is 5.6 to 10.2 h.
Indications and Usage
Adjunct in treatment of all forms of parkinsonism (postencephalitic, arteriosclerotic, and idiopathic); adjuvant therapy with levodopa for control of drug-induced extrapyramidal disorders.Sustained-release
Maintenance therapy after patients have been stabilized on tablets or elixir.
Dosage and AdministrationParkinsonism
PO 1 or 2 mg first day; increase by 3 mg increments at intervals of 3 to 5 days, until 6 to 10 mg given daily in divided doses. Some postencephalitic patients may require total daily dose of 12 to 15 mg. Usually given 3 times daily at mealtimes. High doses may be taken 4 times daily, at mealtimes and at bedtime.Concomitant use with other anticholinergics
Gradually initiate trihexyphenidyl with progressive reduction of other anticholinergic.Drug-Induced Extrapyramidal Disorders
Amount and frequency is individualized. Start with single 1 mg dose. If symptoms are not controlled in few hours, progressively increase until controlled. Daily dosage usually ranges 5 to 15 mg in divided doses.Sustained-Release
Not for initial therapy. Once patient is stabilized, may switch on equipotent daily basis. Give as single dose after breakfast or in twice-daily doses 12 h apart.
Store at room temperature in light-resistant container. Avoid freezing the elixir.
Schizophrenic symptoms may worsen; haloperidol levels may decrease and tardive dyskinesia may develop.Phenothiazines
Actions of phenothiazines may be decreased.
Laboratory Test Interactions
None well documented.
Tachycardia; palpitations; hypotension.
Dizziness; nervousness; psychiatric manifestations such as delusions or hallucinations; mental confusion; agitation; disturbed behavior.
Blurred vision; angle-closure glaucoma; difficulty swallowing.
Dry mouth; nausea; vomiting; constipation; suppurative parotitis; dilation of colon; paralytic ileus.
Urinary retention; urinary hesitancy; impotence.
Fever; flushing; decreased sweating; heat illness.
Category C .
Safety and efficacy not established.
More susceptible to adverse reactions.
Special Risk Patients
Use drug with caution in patients with tachycardia, arrhythmias, hypertension, hypotension, prostatic hypertrophy, liver or kidney disorders, obstructive disease of GI tract.
Concomitant use of other drugs with anticholinergic effects will have additive effects.
Give with caution during hot weather. Severe anhidrosis and fatal hyperthermia may occur.
Incipient narrow-angle glaucoma may be precipitated by drug use; therefore, closely monitor patient for symptoms and evaluate IOP at regular, periodic intervals.
CNS depression, dry skin, dry mucous membranes, fever, dilated or sluggish pupils, respiratory depression, circulatory collapse, coma.
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