trihexyphenidyl

trye-hex-ee-FEN-i-dill

Therapeutic Classification: antiparkinson agents

Pharmacologic Classification: anticholinergics

BEERS REMS

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/Excretion: Excreted mostly in urine.

Half-Life: 3.7 hr.

(antiparkinson effects)

ROUTE	ONSET	PEAK	DURATION
PO	1 hr	2–3 hr	6–12 hr

Contraindicated in:

Hypersensitivity;
Angle-closure glaucoma;
Acute hemorrhage;
Tachycardia secondary to cardiac insufficiency;
Thyrotoxicosis;
Known alcohol intolerance (elixir only).

Use Cautiously in:

Intestinal obstruction or infection;
Prostatic hyperplasia;
Chronic renal, hepatic, pulmonary, or cardiac disease;
OB: Safety not established in pregnancy;
Lactation: Safety not established in breastfeeding;
Pedi: Safety and effectiveness not established in children;
Geri: Appears on Beers list. Not recommended for prevention or treatment of extrapyramidal symptoms due to antipsychotics in older adults; more effective agents available for treatment of Parkinson's disease. Avoid use in older adults.

CV: orthostatic hypotension, tachycardia

Derm: ↓sweating

EENT: blurred vision, mydriasis

GI: dry mouth, nausea, constipation, vomiting

GU: urinary hesitancy, urinary retention

Neuro: dizziness, nervousness, confusion, drowsiness, headache, psychoses, weakness

Drug-drug:

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.

Drug-Natural Products:

↑anticholinergic effects with angel’s trumpet, jimson weed, and scopolia.

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

(Generic available)

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

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.

PO: 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.

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.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.
Emphasize the importance of routine follow-up exams.

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.

~~Artane~~

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Action ⬆ ⬇

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Contraind./Precautions ⬆ ⬇

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Interactions ⬆ ⬇

Route/Dosage ⬆ ⬇

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Assessment ⬆ ⬇

Implementation ⬆ ⬇

Patient/Family Teaching ⬆ ⬇

Evaluation/Desired Outcomes ⬆ ⬇

US Brand Names ⬆