Aparkane , Apo-Trihex , Novohexidyl
Classifications: anticholinergic; antiparkinson agent; anti-muscarinic; antispasmodic; Therapeutic: antiparkinson; antispasmodic
Pregnancy Category: C
2 mg, 5 mg tablets; 2 mg/5 mL elixir
Synthetic tertiary amine anticholinergic agent similar to atropine. Thought to act by blocking excess of acetylcholine at
certain cerebral synaptic sites. Relaxes smooth muscle by direct effect and by atropinelike blocking action on the parasympathetic
Anticholinergic agent diminishes the characteristic tremor of Parkinson's disease. Antispasmodic action appears to be one-half
that of atropine.
Symptomatic treatment of all forms of parkinsonism (arteriosclerotic, idiopathic, postencephalitic). Also to prevent or control
drug-induced extrapyramidal disorders.
Huntington's chorea, spasmodic torticollis.
Narrow-angle glaucoma; tardive dyskinesia; pregnancy (category C), lactation. Safe use in children is not established.
History of drug hypersensitivities; arteriosclerosis; hypertension; cardiac disease, kidney or liver disorders; myasthenia
gravis; alcoholism; obstructive diseases of GI or genitourinary tracts; older adults with prostatic hypertrophy.
Route & Dosage
Adult: PO 1 mg day 1, 2 mg day 2, then increase by 2 mg q35d up to 610 mg/d in 3 or more divided doses (max: 15 mg/d)
Adult: PO 515 mg/d in divided doses
- Give before or after meals, depending on how patient reacts. Older adults and patients prone to excessive salivation (e.g.,
postencephalitic parkinsonism) may prefer to take drug after meals. If drug causes excessive mouth dryness, it may be better
given before meals, unless it causes nausea.
- Once stabilized on conventional dosage forms, patient may be switched to sustained release capsules to permit once- or twice-a-day
- Do not crush or chew sustained release capsules. These must be swallowed whole.
- Store at 15°30° C (59°86° F) in tight container unless otherwise directed.
Adverse Effects (≥1%) GI: Dry mouth, nausea, constipation
. Special Senses: Blurred vision,
mydriasis, photophobia, angle-closure glaucoma
Urinary hesitancy or retention. CNS: Dizziness, nervousness, insomnia
, drowsiness, confusion, agitation, delirium, psychotic manifestations, euphoria. CV:
Tachycardia, palpitations, hypotension, orthostatic hypotension. Body as a Whole:
Reduces therapeutic effects of chlorpromazine, haloperidol, phenothiazines
; increases bioavailability of digoxin; mao inhibitors
potentiate actions of trihexyphenidyl. Herbal: Betel nut
may increase risk of extrapyramidal symptoms
Readily from GI tract. Onset:
Within 1 h. Peak:
23 h. Duration:
612 h. Elimination:
Assessment & Drug Effects
- Be aware that incidence and severity of adverse effects are usually dose related and may be minimized by dosage reduction.
Older adults appear more sensitive to usual adult doses.
- Monitor vital signs. Pulse is a particularly sensitive indicator of response to drug. Report tachycardia, palpitations,
paradoxical bradycardia, or fall in BP.
- Assess for and report severe CNS stimulation (see ADVERSE EFFECTS) that occurs with high doses, and in patients with arteriosclerosis, or those with history of hypersensitivity to other
- In patients with severe rigidity, tremors may appear to be accentuated during therapy as rigidity diminishes.
- Monitor daily I&O if patient develops urinary hesitancy or retention. Voiding before taking drug may relieve problem.
- Check for abdominal distention and bowel sounds if constipation is a problem.
- Monitor intraocular pressure at regular intervals.
- Provide close follow-up care. Tolerance may develop, necessitating dosage adjustment or use of combination therapy. Patients
≥60 y frequently develop sensitivity to drug action.
Patient & Family Education
- Learn measures to relieve drug-induced dry mouth; rinse mouth frequently with water and suck ice chips, sugarless gum, or
hard candy. Maintain adequate total daily fluid intake.
- Avoid excessive heat because drug suppresses perspiration and, therefore, heat loss.
- Do not to engage in potentially hazardous activities requiring alertness and skill. Drug causes dizziness, drowsiness, and
blurred vision. Help walking may be indicated.