DITROPAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DITROPAN (DITROPAN).
Antimuscarinic/anticholinergic agent; competitively inhibits acetylcholine at muscarinic receptors, decreasing smooth muscle tone in the bladder.
| Metabolism | Primarily metabolized by CYP3A4; minor pathways include CYP3A5. Main metabolite: N-desethyloxybutynin (active). |
| Excretion | Renal excretion accounts for approximately 60-80% of elimination, with about 10% as unchanged drug and the rest as metabolites (primarily desethyloxybutynin). Fecal elimination is minimal (<1%). |
| Half-life | Terminal elimination half-life of oxybutynin is approximately 2-3 hours, while its active metabolite desethyloxybutynin has a half-life of about 2-4 hours. Clinical context: Despite short half-life, extended-release formulations allow once-daily dosing. |
| Protein binding | Oxybutynin: approximately 91-93% bound to plasma proteins, primarily alpha1-acid glycoprotein and albumin. Desethyloxybutynin: approximately 97% bound. |
| Volume of Distribution | Oxybutynin: Vd is approximately 1.7-2.7 L/kg, indicating extensive tissue distribution. Desethyloxybutynin: Vd about 1.2 L/kg. |
| Bioavailability | Immediate-release oral: approximately 6% (extensive first-pass metabolism) but active metabolite contributes; Extended-release oral: approximately 11-14% (relative bioavailability); Transdermal patch: steady-state bioavailability about 1.5-2.7% (lower first-pass). |
| Onset of Action | Immediate-release oral: 30-60 minutes; Extended-release oral: 1-2 hours; Transdermal patch: 24-48 hours (steady state), with initial effects in 4-6 hours; Topical gel: 1-2 hours. |
| Duration of Action | Immediate-release oral: 6-8 hours; Extended-release oral: 24 hours; Transdermal patch: 4 days (system worn for 3-4 days); Topical gel: approximately 24 hours. |
5 mg orally 2-3 times daily. Maximum 5 mg 4 times daily. Immediate-release formulation.
| Dosage form | SYRUP |
| Renal impairment | No specific guidelines. Use caution in renal impairment; dose reduction may be considered in severe impairment (CrCl <30 mL/min). |
| Liver impairment | No specific guidelines. Use caution in hepatic impairment; dose reduction may be considered in Child-Pugh class C. |
| Pediatric use | Children ≥5 years: 5 mg orally 2-3 times daily. Maximum 5 mg 3 times daily. Not recommended in children <5 years. |
| Geriatric use | Start at 2.5 mg orally 2 times daily; increase gradually. Increased risk of cognitive impairment, constipation, and urinary retention. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DITROPAN (DITROPAN).
| Breastfeeding | Limited data; M/P ratio unknown. May suppress lactation via anticholinergic effect. Use caution due to potential infant anticholinergic effects (e.g., tachycardia, constipation). |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Potential anticholinergic effects in fetus with third-trimester use (e.g., meconium ileus, neonatal respiratory depression). |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
["Urinary retention","Gastric retention","Uncontrolled narrow-angle glaucoma","Hypersensitivity to oxybutynin or any component"]
| Precautions | ["Angioedema","Central nervous system effects (e.g., dizziness, somnolence)","Exacerbation of myasthenia gravis","Heat stroke due to decreased sweating","Urinary retention","Gastric retention","Hepatic impairment"] |
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| Monitor maternal heart rate, blood pressure, and anticholinergic symptoms (dry mouth, blurred vision, urinary retention). In third trimester, observe newborn for CNS depression, anticholinergic toxicity (tachycardia, constipation). |
| Fertility Effects | No known direct effects on fertility in animal studies; anticholinergic effects may theoretically impact cervical mucus or implantation, but no human data. |