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Oxybutynin (Ditropan)

Urologicalprescriptionoral · inferred

Non-selective muscarinic (M1-M5) antagonist with additional local anesthetic and spasmolytic effects on detrusor smooth muscle; used for overactive bladder and urinary incontinence. IR 5 mg BID-TID (max 5 mg QID); XL 5-30 mg QD; transdermal patch and topical gel available. Plasma half-life 2-5h IR with first-pass formation of N-desethyloxybutynin (active, contributes to anticholinergic AEs). Oral bioavailability very low (~6%) due to extensive first-pass CYP3A4 metabolism, rationale for transdermal formulations. Heavy anticholinergic burden (dry mouth, constipation, cognitive impairment, especially in elderly).

Projected serum levels — 5 mg, once daily

Oxybutynin (Ditropan)
Oxybutynin (Ditropan) modeled serum levels, 5 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 0.25 0.50 0.75 1 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 5 mg once daily (oral).

Modeled steady state after ~1 days: peak ≈ 0.22 mg, trough ≈ 0.000 mg body load. Population-based estimate over 15 days for a 5 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Urological
Route modeled
Oral
Model confidence
inferred
Half-life
2.3 h
Common dose
5 mg
Suggested maximum
30 mg/day
Reference dose range
2.5–30 mg (single dose)
Suggested cadence
once daily
Validated against
5 mg oral — Cmax 0.007 mg/L at 1 h

Documented interactions

  • contraindicated
    Carbamazepine (Tegretol) + Oxybutynin (Ditropan) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Oxybutynin (Ditropan) AUC by ~0.20x

  • contraindicated
    Clarithromycin (Biaxin) + Oxybutynin (Ditropan) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Oxybutynin (Ditropan) AUC by ~10.00x

  • contraindicated
    Dasatinib (Sprycel) + Oxybutynin (Ditropan) CYP inhibition

    Dasatinib (Sprycel) time_dependent_inhibitor of CYP3A4 predicted to change Oxybutynin (Ditropan) AUC by ~5.00x

  • contraindicated
    Diltiazem + Oxybutynin (Ditropan) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Oxybutynin (Ditropan) AUC by ~10.00x

  • contraindicated
    Efavirenz (Sustiva) + Oxybutynin (Ditropan) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Oxybutynin (Ditropan) AUC by ~0.12x

  • contraindicated
    Grapefruit (whole fruit) + Oxybutynin (Ditropan) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Oxybutynin (Ditropan) AUC by ~10.00x

Serum checks 208 modeled interaction pairings for oxybutynin (ditropan) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. A double-blind crossover comparison of the safety and efficacy of oxybutynin and propantheline in elderly patients with detrusor instability Douchamps J et al. · European Journal of Clinical Pharmacology, 1988 DOI

    Classical comparator trial characterizing oxybutynin efficacy and anticholinergic tolerability profile in elderly patients.

  2. Pharmacokinetic and safety comparison of a controlled-release oxybutynin formulation versus immediate-release oxybutynin in older adults with urge urinary incontinence Gupta SK et al. · Journal of Urology, 1999 DOI

    PK and tolerability comparison showing XL formulation achieves smoother plasma profile with reduced peak-related dry-mouth AEs.

2 published studies referenced in the app, each with a plain-language summary.