DISIPAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DISIPAL (DISIPAL).
Disipal (orphenadrine) is a centrally acting anticholinergic agent that blocks muscarinic acetylcholine receptors in the central nervous system, reducing cholinergic overactivity. It also exhibits local anesthetic and antihistaminic properties.
| Metabolism | Hepatic metabolism via N-demethylation and N-oxide formation, primarily by CYP450 enzymes (CYP3A4, CYP2D6). |
| Excretion | Primarily renal (approximately 70-80% as unchanged drug and metabolites), with the remainder via biliary/fecal elimination. |
| Half-life | Terminal elimination half-life: 12-15 hours; steady-state achieved after 3-5 days. |
| Protein binding | Approximately 90-95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 5-10 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability: 70-80% (first-pass metabolism limited); IM: 90-95%; IV: 100%. |
| Onset of Action | Oral: within 30-60 minutes; intramuscular: 10-15 minutes; intravenous: 2-5 minutes. |
| Duration of Action | 6-12 hours for motor symptoms; shorter for mental effects (2-4 hours). Clinical note: Dosing frequency may need adjustment based on response. |
| Molecular Weight | 311.46 |
5 mg oral twice daily, titrated to a maximum of 15 mg/day in divided doses.
| Dosage form | TABLET |
| Renal impairment | GFR <30 mL/min: reduce dose by 50% or increase dosing interval to 12-24 hours. |
| Liver impairment | Child-Pugh class B: reduce dose by 50%; class C: avoid use. |
| Pediatric use | 0.02-0.05 mg/kg/dose twice daily, max 5 mg/day. |
| Geriatric use | Initiate at 2.5 mg daily, titrate slowly; monitor for anticholinergic effects and falls. |
| 1st trimester | Avoid; anticholinergic effects and potential teratogenicity, especially during organogenesis. |
| 2nd trimester | Use only if benefit outweighs risk; may cause fetal tachycardia or anticholinergic effects. |
| 3rd trimester | Avoid near term; risk of neonatal anticholinergic effects (e.g., ileus, sedation). |
Clinical note
Comprehensive clinical and safety monograph for DISIPAL (DISIPAL).
| Placental transfer | Crosses placenta; extent not well quantified but anticholinergic effects observed in neonates. |
| Breastfeeding | Excreted into breast milk in small amounts; potential for anticholinergic effects in infant. Use with caution, monitor for sedation, irritability, or feeding difficulties. |
| Lactation Rating |
■ FDA Black Box Warning
None
| Serious Effects |
Closed-angle glaucomaMyasthenia gravisSevere liver diseaseHypersensitivity to orphenadrineUrinary retention
| Precautions | Anticholinergic effects: confusion, hallucinations, urinary retention, constipation, blurred vision, May exacerbate glaucoma, myasthenia gravis, prostatic hypertrophy, or gastrointestinal obstruction, Central nervous system effects: drowsiness, dizziness (avoid driving or operating heavy machinery), Risk of toxicity in elderly patients or those with hepatic/renal impairment, Potential for abuse and dependence |
| Food/Dietary | No specific food restrictions. However, avoid excessive alcohol consumption as it may exacerbate CNS side effects. Grapefruit juice may theoretically alter drug metabolism, but no significant interaction reported. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | First trimester: Limited human data; animal studies show no consistent teratogenicity. Second and third trimesters: Risk of neonatal anticholinergic effects (e.g., decreased GI motility, urinary retention). No known major malformation risk. |
| Fetal Monitoring | Monitor maternal heart rate, blood pressure, gastrointestinal motility, and urinary output. Assess neonatal heart rate, feeding behavior, and bowel function postnatally. |
| Fertility Effects | Anticholinergic properties may reduce fertility in females via cervical mucus thickening; no known effect on male fertility. |
| Clinical Pearls | DISIPAL (orphenadrine) is an anticholinergic agent used primarily for the treatment of Parkinson's disease and drug-induced extrapyramidal reactions. Avoid in patients with narrow-angle glaucoma, myasthenia gravis, or obstructive GI disorders. Onset of action is rapid (30-60 min) but anticholinergic side effects (dry mouth, blurred vision, urinary retention) are common. Taper gradually to avoid withdrawal. May potentiate CNS depression with alcohol or other sedatives. |
| Patient Advice | Take exactly as prescribed; do not stop suddenly as withdrawal symptoms may occur. · Avoid alcohol and other CNS depressants (sleeping pills, tranquilizers) as they can increase drowsiness and dizziness. · Report blurred vision, difficulty urinating, or severe constipation immediately. · Use caution when driving or operating machinery until you know how this medication affects you. · Drink plenty of fluids and use sugarless gum or candy to relieve dry mouth. · Do not crush or chew extended-release tablets; swallow whole with a full glass of water. |