PARSIDOL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PARSIDOL (PARSIDOL).
Parsidol (ethopropazine) is a phenothiazine derivative that acts as an anticholinergic agent. It inhibits the action of acetylcholine at muscarinic receptors, thereby reducing cholinergic activity in the basal ganglia and restoring the balance between dopaminergic and cholinergic neurotransmission. It also has some dopamine reuptake inhibition and antihistaminic properties.
| Metabolism | Primarily hepatic via cytochrome P450 enzymes (CYP2D6), with metabolites excreted in urine and bile. The exact metabolic pathway is not fully elucidated. |
| Excretion | Renal: 60-70% as unchanged drug; biliary/fecal: 15-20% as metabolites; minor respiratory elimination. |
| Half-life | Terminal elimination half-life: 12-24 hours (prolonged in elderly and renal impairment, requiring dose adjustment). |
| Protein binding | 90-95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 7-10 L/kg (high, indicating extensive tissue distribution with accumulation in CNS and adipose tissue). |
| Bioavailability | Oral: 40-50% due to first-pass metabolism; IM: ~75%. |
| Onset of Action | Oral: 30-60 minutes; IM: 10-20 minutes; IV: 5-10 minutes. |
| Duration of Action | Oral: 6-12 hours; IM/IV: 4-6 hours; duration may be extended with repeated dosing due to accumulation. |
Oral: 2.5-5 mg twice daily, gradually increased to 5-10 mg three times daily; maximum 60 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-89 mL/min: Reduce dose by 50%; GFR <30 mL/min: Avoid use or extend dosing interval to 12-24 hours. |
| Liver impairment | Child-Pugh A: No adjustment; Child-Pugh B: Reduce dose by 50%; Child-Pugh C: Avoid use. |
| Pediatric use | Not recommended for children under 12 years; for age ≥12 years: 0.5-1 mg/kg/day divided every 6-12 hours, max 20 mg/day. |
| Geriatric use | Initial dose 1.25-2.5 mg once or twice daily; titrate slowly. Avoid if possible due to anticholinergic side effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PARSIDOL (PARSIDOL).
| Breastfeeding | No data on M/P ratio. Excretion into breast milk likely low due to high protein binding (90-95%). Consider risk of EPS in the infant; use with caution. |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no teratogenicity at clinically relevant doses. Second and third trimesters: No evidence of fetal harm; risk of extrapyramidal symptoms (EPS) in neonates if used near term. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to ethopropazine or any phenothiazine","Narrow-angle glaucoma","Obstructive uropathy (e.g., prostatic hypertrophy)","Pyloric or duodenal obstruction","Myasthenia gravis"]
| Precautions | ["May cause drowsiness, dizziness, or blurred vision; patients should not drive or operate machinery until effects are known.","Caution in patients with glaucoma, prostatic hypertrophy, urinary retention, or gastrointestinal obstruction.","May exacerbate tardive dyskinesia or other movement disorders.","Abrupt withdrawal may precipitate parkinsonian crisis.","Use with caution in elderly patients due to increased sensitivity to anticholinergic effects.","Hepatic or renal impairment may require dose adjustment."] |
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| Monitor maternal EPS, neuroleptic malignant syndrome (NMS), and glucose levels. Fetal monitoring for growth and movement; neonatal monitoring for EPS after delivery if used in third trimester. |
| Fertility Effects | May increase prolactin, potentially causing menstrual irregularities and reduced fertility. No direct evidence of permanent fertility impairment. |