DITROPAN XL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DITROPAN XL (DITROPAN XL).
Oxybutynin is a competitive antagonist of muscarinic acetylcholine receptors (M1, M2, M3 subtypes), reducing detrusor muscle contraction and bladder smooth muscle spasm, thereby increasing bladder capacity and decreasing urge incontinence.
| Metabolism | Primarily hepatic via cytochrome P450 isoenzymes CYP3A4 and CYP3A5; undergoes extensive first-pass metabolism to active and inactive metabolites, including desethyloxybutynin (active). |
| Excretion | Approximately 50% of the administered dose is excreted in urine as unchanged drug and its active metabolite, N-desethyloxybutynin, with the remainder excreted in feces via biliary elimination. |
| Half-life | The terminal elimination half-life of oxybutynin is approximately 12-13 hours for the immediate-release formulation, but for DITROPAN XL, due to its extended-release profile, the effective half-life is extended, allowing once-daily dosing. Clinical context: steady-state is achieved within 3 days of dosing. |
| Protein binding | Approximately 90-95% bound to plasma proteins, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | The apparent volume of distribution (Vd) is approximately 1.2 L/kg, indicating extensive distribution into extravascular tissues. |
| Bioavailability | Oral (extended-release): Bioavailability is approximately 10-20% due to extensive first-pass metabolism via cytochrome P450 3A4 isoenzymes. |
| Onset of Action | Oral (extended-release): Onset of anticholinergic effects (e.g., reduction in urinary frequency) is typically observed within 1-2 hours following administration. |
| Duration of Action | Oral (extended-release): Duration of action is approximately 24 hours, supporting once-daily dosing. Clinical notes: controlled release maintains therapeutic plasma concentrations over the dosing interval. |
| Molecular Weight | 357.5 |
Oral: 5 to 10 mg once daily; maximum 30 mg once daily.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | CrCl <30 mL/min: Use not recommended; no specific dose adjustment available. |
| Liver impairment | Child-Pugh Class A: No adjustment; Child-Pugh Class B: Use with caution, consider dose reduction; Child-Pugh Class C: Use not recommended. |
| Pediatric use | Children ≥6 years: Oral, 5 mg once daily, may increase to 10 mg once daily based on response and tolerability. |
| Geriatric use | Start with 5 mg once daily; titrate cautiously due to increased anticholinergic sensitivity and risk of cognitive impairment. |
| 1st trimester | Oxybutynin crosses the placenta. Limited human data; animal studies show no teratogenicity at clinically relevant doses. Use only if clearly needed. |
| 2nd trimester | No specific risks identified; consider potential anticholinergic effects on fetus. Use cautiously. |
| 3rd trimester | Risk of neonatal anticholinergic effects (e.g., constipation, urinary retention) if used near term. Use with caution. |
Clinical note
Comprehensive clinical and safety monograph for DITROPAN XL (DITROPAN XL).
| Placental transfer | Oxybutynin crosses the placenta; exact degree not well characterized. Molecular weight (357.5 Da) suggests potential for transfer. |
| Breastfeeding | Oxybutynin is excreted into breast milk in small amounts. No adverse effects have been reported in nursing infants. Due to limited data, caution is advised. Monitor infant for anticholinergic effects. |
■ FDA Black Box Warning
None
| Serious Effects |
Urinary retentionGastric retentionUncontrolled narrow-angle glaucomaHypersensitivity to oxybutynin or any component
| Precautions | May worsen myasthenia gravis; use caution in patients with gastrointestinal obstructive disorders, decreased gastrointestinal motility, ulcerative colitis, hiatal hernia with reflux esophagitis, and hepatic or renal impairment. May cause heat prostration in hot environments. Avoid use in patients with bladder outflow obstruction or narrow-angle glaucoma. |
| Food/Dietary | Grapefruit juice may increase absorption; avoid concurrent intake. Alcohol may enhance drowsiness and anticholinergic effects. High-fat meals may reduce peak concentration but not overall absorption; consistent timing with meals recommended. |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category B. Oxybutynin did not demonstrate teratogenicity in animal studies at doses up to 20 times the human dose. However, no adequate human studies exist. Avoid in first trimester unless benefit outweighs risk. In second and third trimesters, use caution; oxybutynin may cross the placenta and cause anticholinergic effects in the fetus (e.g., tachycardia, meconium ileus). |
| Fetal Monitoring | Monitor maternal heart rate and blood pressure for anticholinergic side effects. Fetal heart rate monitoring is not routinely required but may be considered if high doses are used. In neonates, monitor for transient anticholinergic effects (e.g., decreased bowel sounds, tachycardia). |
| Fertility Effects | Oxybutynin may have anticholinergic effects on reproductive function, but no specific human data on fertility impact. Animal studies show no significant effect on fertility. In theory, it could cause dry mucous membranes or affect sexual function; no dose adjustment recommended for fertility. |
| Clinical Pearls | Extended-release formulation allows once-daily dosing. Avoid use in patients with narrow-angle glaucoma, myasthenia gravis, or gastrointestinal obstructive conditions. May exacerbate symptoms of hiatal hernia or gastroesophageal reflux due to smooth muscle relaxation. Monitor for anticholinergic effects including dry mouth, constipation, blurred vision, and cognitive impairment in elderly. Doses >5 mg may increase risk of QT prolongation. For neurogenic bladder, preferred as second-line after behavioral modifications. |
| Patient Advice | Take once daily with or without food. Swallow whole; do not crush, chew, or divide. · Drink plenty of fluids to prevent constipation and heat prostration. · Avoid activities requiring mental alertness (e.g., driving) until effects are known. · Report severe abdominal pain, difficulty urinating, or blurred vision to your doctor. · Store at room temperature, away from moisture and heat. |