Trihexyphenidyl

Trihexyphenidyl May be taken with or without food. Best taken w/ food. However, can be taken before meals if there is excessive dry mouth.

Narrow angle glaucoma.

Patient with CV disease including hypertension, arteriosclerosis; history of drug idiosyncrasy; myasthenia gravis, gastrointestinal obstruction, prostatic hyperplasia and/or urinary stricture or retention. Use during hot weather or exercise. Not recommended for the treatment of tardive dyskinesia. Avoid abrupt withdrawal. Renal and hepatic impairment. Elderly. Pregnancy and lactation.

Significant: Anticholinergic effects (e.g. blurred vision, constipation, urinary retention, xerostomia), may precipitate angle closure with increased IOP, blindness (due to narrow angle glaucoma aggravation), worsening of myasthenia gravis; withdrawal symptoms, exacerbation of parkinsonism (after abrupt discontinuation).
Cardiac disorders: Tachycardia.
Eye disorders: Mydriasis.
Gastrointestinal disorders: Mild nausea, vomiting.
General disorders and administration site conditions: Weakness, pyrexia, thirst.
Nervous system disorders: Dizziness, headache, impaired immediate and short-term memory.
Psychiatric disorders: Agitation, confusion, insomnia, delirium, hallucination, euphoria, nervousness, restlessness.
Renal and urinary disorders: Urinary hesitancy.
Respiratory, thoracic and mediastinal disorders: Decreased bronchial secretion.
Skin and subcutaneous tissue disorders: Rash, dry skin.
Vascular disorders: Flushing.
Potentially Fatal: Severe anhidrosis and fatal hyperthermia; neuroleptic malignant syndrome (associated with discontinuation or dose reduction).

PO: C

This drug may cause dizziness, mild nausea, or blurred vision, if affected, do not drive or operate machinery.

Perform gonioscopic examination prior to initiation of therapy. Closely monitor IOP regularly. Assess for anticholinergic adverse reactions as clinically indicated (particularly during prolonged treatment).

Symptoms: Dryness of the skin, flushing, dilated pupils, dry mouth, nausea, vomiting, tachycardia, rapid respiration, hyperpyrexia, hypertension, rashes on the face or upper trunk, confusion, restlessness, hallucinations, paranoid and psychotic reactions, incoordination, delirium, occasional convulsions, CNS depression that may occur with coma, circulatory and respiratory failure. Management: Symptomatic and supportive treatment. Maintain adequate airway. Correct hypoxia and acidosis. May administer diazepam to control excitement and convulsions, but consider the risk for CNS depression.

Concomitant use with TCAs, MAOIs, clozapine, amantadine, disopyramide, and phenothiazines may result in enhanced anticholinergic effects. May increase the risk of tardive dyskinesia when used concomitantly with neuroleptics. May antagonise the effect of parasympathomimetics, domperidone and metoclopramide. May reduce the absorption of levodopa. Concomitant administration with barbiturates and opioids may have additive effects, thus, the potential for abuse exists.

Enhanced sedative effects with alcohol.

Description:
Mechanism of Action: Trihexyphenidyl is a tertiary amine antimuscarinic antiparkinsonian agent that has a direct inhibitory effect on the parasympathetic nervous system. It also exhibits a direct antispasmodic action on smooth muscle and has weak mydriatic, antisecretory and cardiovagal blocking effects.
Onset: Within 1 hour.
Duration: 6-12 hours.
Pharmacokinetics:
Absorption: Rapidly and well absorbed from the gastrointestinal tract. Time to peak plasma concentration: 1.3 hours.
Metabolism: Undergoes hydroxylation of the alicyclic groups.
Excretion: Via urine (as unchanged drug) and bile. Elimination half-life: 33 hours.

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 5572, Trihexyphenidyl. https://pubchem.ncbi.nlm.nih.gov/compound/Trihexyphenidyl. Accessed May 27, 2025.

Store between 20-25°C.

Antiparkinsonian Drugs

N04AA01 - trihexyphenidyl ; Belongs to the class of tertiary amines anticholinergic agents. Used in the management of Parkinson's disease.

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Trihexyphenidyl. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 11/03/2025.