PAGITANE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PAGITANE (PAGITANE).
Trihexyphenidyl is a centrally acting anticholinergic agent that blocks muscarinic acetylcholine receptors (M1, M2, M3, M4, M5) in the basal ganglia. This antagonism restores the balance between cholinergic and dopaminergic activity, reducing extrapyramidal side effects.
| Metabolism | Primarily hepatic via hydroxylation and conjugation, with minor involvement of CYP2C19 and CYP3A4. Excreted in urine as metabolites and unchanged drug. |
| Excretion | Renal (approximately 60% as unchanged drug and metabolites), biliary/fecal (30-40%). |
| Half-life | 12-16 hours in adults; clinically significant accumulation occurs with once-daily dosing due to long half-life. |
| Protein binding | Approximately 75-80% bound to albumin and alpha1-acid glycoprotein. |
| Volume of Distribution | 1.5-2.5 L/kg; high Vd indicates extensive tissue distribution and slow elimination. |
| Bioavailability | Oral: 30-40% due to extensive first-pass metabolism; IM: 100% (assumed). |
| Onset of Action | Oral: 2-3 hours; IM: 30-60 minutes. |
| Duration of Action | Oral: 6-12 hours; IM: 2-4 hours. Clinical effects may persist longer due to extended half-life. |
2 mg orally three times daily, titrated upward as needed; maximum 8 mg orally three times daily.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment (CrCl <30 mL/min) due to potential for increased anticholinergic effects. |
| Liver impairment | Use with caution in hepatic impairment; no specific Child-Pugh based guidelines available. Monitor for increased adverse effects. |
| Pediatric use | For children (age ≥6 years): 1 mg orally daily, titrated in increments of 1 mg every 7 days; maximum 6 mg daily divided into 3 doses. |
| Geriatric use | Initiate at 1 mg orally twice daily; titrate slowly. Increased susceptibility to anticholinergic effects (e.g., confusion, constipation, urinary retention). |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PAGITANE (PAGITANE).
| Breastfeeding | Excreted into breast milk; M/P ratio not established. Theoretical risk of anticholinergic effects in infant. Use with caution, weighing benefit vs risk. |
| Teratogenic Risk | First trimester: Limited data; possible increased risk of congenital malformations (limb defects) reported with anticholinergics in animal studies. Second/third trimester: Risk of fetal anticholinergic effects (e.g., tachycardia, meconium ileus); neonatal withdrawal symptoms reported. Avoid if possible. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to trihexyphenidyl or any component","Narrow-angle glaucoma (angle-closure glaucoma)","Obstructive uropathy (e.g., bladder neck obstruction due to prostatic hypertrophy)","Myasthenia gravis","Megaesophagus or achalasia"]
| Precautions | ["May impair mental and/or physical abilities; caution when driving or operating machinery","Use with caution in elderly patients due to increased sensitivity (confusion, agitation)","May exacerbate angle-closure glaucoma, urinary retention, prostatic hypertrophy, and gastrointestinal obstructive disorders","May cause anhidrosis and hyperthermia, especially in hot environments or with strenuous exercise","Abrupt withdrawal can precipitate parkinsonian crisis or withdrawal emergent hyperpyrexia and confusion"] |
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| Monitor fetal growth and heart rate if used in pregnancy. Observe neonate for anticholinergic effects (e.g., feeding difficulty, constipation, urinary retention). |
| Fertility Effects | May impair male or female fertility due to anticholinergic effects (e.g., reduced libido, erectile dysfunction, altered spermatogenesis). Reversible upon discontinuation. |