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. |
| Molecular Weight | 357.49 |
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 | Limited human data; oxybutynin crosses placenta; teratogenic risk in animal studies at high doses; use only if benefit outweighs risk. |
| 2nd trimester | Same as T1; consider alternative agents with more safety data. |
| 3rd trimester | May cause neonatal anticholinergic effects (e.g., ileus, respiratory depression) if used near term; avoid or use with caution. |
Clinical note
Comprehensive clinical and safety monograph for DITROPAN (DITROPAN).
| Placental transfer | Oxybutynin crosses the placenta in humans; degree of transfer not quantified but expected due to molecular weight and lipophilicity. |
| Breastfeeding | Oxybutynin is excreted into breast milk in small amounts; no reports of adverse effects in infants. However, monitor infant for anticholinergic effects (e.g., dry mouth, constipation). Consider alternative agents with more data. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Uncontrolled narrow-angle glaucomaUrinary retentionGastric retentionMyasthenia gravisSevere ulcerative colitisToxic megacolon
| 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 |
| Food/Dietary | No specific restrictions, but high-fat meals may increase absorption of extended-release formulation. Avoid alcohol and excessive caffeine (coffee, tea, cola) as they may exacerbate bladder irritability and anticholinergic side effects. Grapefruit juice may theoretically increase oxybutynin levels; monitor for side effects. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) per LactMed; caution advised |
| 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 | 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. |
| Clinical Pearls | Ditropan (oxybutynin) is an anticholinergic agent used for overactive bladder. Onset of action is within 30-60 minutes; peak effect at 3-6 hours. Use with caution in elderly due to increased risk of confusion, falls, and anticholinergic side effects. Extended-release formulation (Ditropan XL) has once-daily dosing and improved tolerability. Contraindicated in narrow-angle glaucoma, gastrointestinal obstruction, and myasthenia gravis. May exacerbate dementia or cognitive impairment. |
| Patient Advice | Take Ditropan exactly as prescribed, usually 2-3 times daily for immediate-release or once daily for extended-release. · Avoid alcohol and other CNS depressants as they may increase drowsiness and dizziness. · Drink plenty of fluids unless otherwise advised, but avoid excessive caffeine or diuretics that may worsen bladder symptoms. · Do not crush or chew extended-release tablets; swallow whole. · Report severe constipation, difficulty urinating, blurred vision, confusion, or rapid heartbeat immediately. · May cause dry mouth, use sugar-free gum or candy for relief. · Use caution when driving or operating machinery until you know how Ditropan affects you. · Store at room temperature away from moisture and heat. |