brands

Class

• Antiparkinson agent; anticholinergic

TRIHEXYPHENIDYL commonly prescribed for

(Bold for FDA approved)

How TRIHEXYPHENIDYL works

• Diminishes the excess acetylcholine activity caused by removal of dopamine inhibition when dopamine receptors are blocked

• May also inhibit the reuptake and storage of dopamine at central dopamine receptors, prolonging dopamine action

How long until TRIHEXYPHENIDYL works

• For drug-induced parkinsonism and in Parkinson’s disease, onset of action can be within minutes or hours

Notable Side Effects

• Dry mouth, blurred vision, diplopia

• Confusion, hallucinations

• Constipation, nausea, vomiting

• Dilation of colon

• Erectile dysfunction

Life Threatening Side Effects

• Angle-closure glaucoma

• Heat stroke, especially in elderly patients

• Tachycardia, cardiac arrhythmias, hypotension

• Urinary retention

• Anticholinergic agents such as trihexyphenidyl can exacerbate or unmask tardive dyskinesia

weight gain

unusual

sedation

common

What to do about TRIHEXYPHENIDYL side effects

• For confusion or hallucinations, discontinue use

• For sedation, lower the dose and/or take the entire dose at night

• For dry mouth, chew gum or drink water

• For urinary retention, obtain a urological evaluation; may need to discontinue use

usual dosage range

• Drug-induced parkinsonism: 5–15 mg/day

• Parkinsonism: 6–15 mg/day

Dosage Forms

• Tablet 2 mg, 5 mg

• Injection 2 mg/5 mL

long term use

• Safe

• Effectiveness may decrease over time (years) and side effects such as sedation and cognitive impairment may worsen

habit forming

• No

Renal Impairment

• No known effects, but use with caution

Hepatic Impairment

• No known effects, but use with caution

Cardiac Impairment

• Use with caution in patients with known arrhythmias, especially tachycardia

Elderly

• Use with caution

• Elderly patients may be more susceptible to side effects

Children and Adolescents

• Do not use in children ages 3 and younger

• Generalized dystonias may respond to anticholinergic treatment, and young patients usually tolerate the medication better than the elderly

• Usual dose is 0.05 mg/kg once or twice daily

Pregnancy

• Effective June 30, 2015, the FDA requires changes to the content and format of pregnancy and lactation information in prescription drug labels, including the elimination of the pregnancy letter categories; the Pregnancy and Lactation Labeling Rule (PLLR or final rule) applies only to prescription drugs and will be phased in gradually for drugs approved on or after June 30, 2001

• Controlled studies have not been conducted in pregnant women

Breast Feeding

• Unknown if trihexyphenidyl is secreted in human breast milk, but all psychotropics are assumed to be secreted in breast milk

• Recommended either to discontinue drug or bottle feed unless the potential benefit to the mother justifies the potential risk to the child

• Infants of women who choose to breast feed while on trihexyphenidyl should be monitored for possible adverse effects