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Related to trihexyphenidyl: Trihexyphenidyl hydrochloride


an antidyskinetic used as the hydrochloride salt in the treatment of parkinsonism and for the control of drug-induced extrapyramidal reactions (except tardive dyskinesia); administered orally.


(trye-hex-ee-fen-i-dill) ,


(trade name)


Therapeutic: antiparkinson agents
Pharmacologic: anticholinergics
Pregnancy Category: C


Adjunct in the management of parkinsonian syndrome of many causes, including drug-induced parkinsonism.


Inhibits the action of acetylcholine, resulting in:
  • Decreased sweating and salivation,
  • Mydriasis (pupillary dilation),
  • Increased heart rate.
Also has spasmolytic action on smooth muscle.
Inhibits cerebral motor centers and blocks efferent impulses.

Therapeutic effects

Diminished signs and symptoms of parkinsonian syndrome (tremors, rigidity).


Absorption: Well absorbed following oral administration.
Distribution: Unknown.
Metabolism and Excretion: Excreted mostly in urine.
Half-life: 3.7 hr.

Time/action profile (antiparkinson effects)

PO1 hr2–3 hr6–12 hr


Contraindicated in: Hypersensitivity; Angle-closure glaucoma; Acute hemorrhage; Tachycardia secondary to cardiac insufficiency; Thyrotoxicosis; Known alcohol intolerance (elixir only).
Use Cautiously in: Geriatric / Pediatric: ↑ risk of adverse reactions; Intestinal obstruction or infection; Prostatic hyperplasia; Chronic renal, hepatic, pulmonary, or cardiac disease; Obstetric / Lactation / Pediatric: Safety not established.

Adverse Reactions/Side Effects

Central nervous system

  • dizziness (most frequent)
  • nervousness (most frequent)
  • confusion
  • drowsiness
  • headache
  • psychoses
  • weakness

Ear, Eye, Nose, Throat

  • blurred vision (most frequent)
  • mydriasis (most frequent)


  • orthostatic hypotension
  • tachycardia


  • dry mouth (most frequent)
  • nausea (most frequent)
  • constipation
  • vomiting


  • urinary hesitancy
  • urinary retention


  • decreased sweating


Drug-Drug interaction

Additive anticholinergic effects with other drugs having anticholinergic properties, including phenothiazines, tricyclic antidepressants, quinidine, and disopyramide.May ↑ the efficacy of levodopa but may ↑ the risk of psychoses.Additive CNS depression with other CNS depressants, including alcohol, antihistamines, opioids, and sedative/hypnotics.Anticholinergics may alter the absorption of other orally administered drugs by slowing motility of the GI tract.Antacids may ↓ absorption.↑ anticholinergic effects with angel’s trumpet and jimson weed and scopolia.


Oral (Adults) 1–2 mg/day initially; ↑ by 2 mg q 3–5 days. Usual maintenance dose is 6–10 mg/day in 3 divided doses (up to 15 mg/day).

Availability (generic available)

Tablets: 2 mg, 5 mg
Elixirlime-mint flavor: 2 mg/5 mL

Nursing implications

Nursing assessment

  • Assess parkinsonian and extrapyramidal symptoms (restlessness or desire to keep moving, rigidity, tremors, pill rolling, mask-like face, shuffling gait, muscle spasms, twisting motions, difficulty speaking or swallowing, loss of balance control) prior to and throughout therapy.
  • Monitor intake and output ratios and assess patient for urinary retention (dysuria, distended abdomen, infrequent voiding of small amounts, overflow incontinence).
  • Patients with mental illness are at risk of developing exaggerated symptoms of their disorder during early therapy with this medication. Withhold drug and report significant behavioral changes.

Potential Nursing Diagnoses

Impaired physical mobility (Indications)
Risk for injury (Indications)
Deficient knowledge, related to medication regimen (Patient/Family Teaching)


  • Oral: Usually administered after meals. May be administered before meals if patient suffers from dry mouth or with meals if gastric distress is a problem. Use calibrated measuring device to ensure accurate dose of elixir.

Patient/Family Teaching

  • Instruct patient to take this drug exactly as directed. If a dose is missed, take as soon as remembered, unless next scheduled dose is within 2 hr; do not double doses.
  • Medication should be tapered gradually when discontinuing or a withdrawal reaction may occur (anxiety, tachycardia, insomnia, return of parkinsonian or extrapyramidal symptoms).
  • May cause drowsiness or dizziness. Advise patient to avoid driving or other activities that require alertness until response to medication is known.
  • Caution patient to change positions slowly to minimize orthostatic hypotension.
  • Instruct patient that frequent rinsing of mouth, good oral hygiene, and sugarless gum or candy may decrease dry mouth. Patient should notify health care professional if dryness persists (saliva substitutes may be used). Also, notify the dentist if dryness interferes with use of dentures.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications, especially cold remedies, or drinking alcoholic beverages.
  • Caution patient that this medication decreases perspiration. Overheating may occur during hot weather. Patient should remain indoors, in an air-conditioned environment, during hot weather.
  • Advise patient to increase activity and bulk and fluid in diet to minimize constipating effects of medication.
  • Advise patient to avoid taking antacids or antidiarrheals within 1–2 hr of this medication.
  • Advise patient to notify health care professional if confusion, rash, urinary retention, severe constipation, or visual changes occur.
  • Emphasize the importance of routine follow-up exams.

Evaluation/Desired Outcomes

  • Decrease in tremors and rigidity and an improvement in gait and balance. Therapeutic effects are usually seen 2–3 days after the initiation of therapy.
  • Resolution of drug-induced extrapyramidal symptoms.


/tri·hex·y·phen·i·dyl/ (tri-hek″sĭ-fen´ĭ-dil) an antidyskinetic used as the hydrochloride salt in the treatment of parkinsonism and for the control of drug-induced extrapyramidal reactions.
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When trihexyphenidyl 5-15 mg/day was given for 15 days to 14 patients who had nocturnal clozapine drooling, a 44% reduction in hypersalivation was reported (Int.
Abuse of anticholinergic drugs was first reported in 1960 with the description of a patient who increased her trihexyphenidyl to achieve antidepressant and euphoriant effects (Bolin 1960).
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