Oxybutynin
Oxybutynin chloride
Also known as: Ditropan XL · Oxytrol · Gelnique · Lyrinel · oxybutinyn HCl · 5058 · MJ4309-1 · oxybutynini hydrochloridum · Oxybutynin HCl · Oxybutynine
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| To decrease bladder contractility (detrusor hyperreflexia) | 0.2 mg/kg | PO | q8-12h | — | 🌎 NA |
| To decrease bladder contractility (detrusor hyperreflexia) | 1.25-5 mg (total dose) | PO | q8-12h | — | 🌎 NA |
| To decrease bladder contractility (detrusor hyperreflexia) | 2-5 mg (total dose) | PO | q8-12h | — | 🌎 NA |
| Detrusor hyperreflexia (refractory incontinence) | 0.2 mg/kg | PO | q8-12h | — | 🌍 EU |
- To decrease bladder contractility (detrusor hyperreflexia): Most dogs are dosed at 1.25-3.75 mg (total dose) q12h. Juvenile animals may require a prolonged dosing interval.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| To decrease bladder contractility (detrusor hyperreflexia) | 0.5-1 mg (total dose) | PO | q8-12h | — | 🌎 NA |
| To decrease bladder contractility (detrusor hyperreflexia) | 0.5-1.25 mg per cat | PO | q8-12h | — | 🌎 NA |
| Detrusor hyperreflexia | 0.5-1.25 mg per cat | PO | q8-12h | — | 🌍 EU |
- To decrease bladder contractility (detrusor hyperreflexia): Juvenile animals may require a prolonged dosing interval.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Oxybutynin is a genitourinary smooth muscle relaxant and anticholinergic medication. In veterinary medicine, it is primarily utilized as an adjunctive therapy for detrusor hyperreflexia (overactive bladder or urge incontinence) in dogs, and in cats with feline leukemia virus (FeLV)-associated detrusor instability.
Key clinical points:
- Acts as a urinary antispasmodic to increase bladder capacity and reduce uninhibited contractions.
- Possesses both direct smooth muscle relaxant properties and anticholinergic effects.
- Clinical Pearl: Because of its anticholinergic nature, it should be used with extreme caution in patients with conditions exacerbated by decreased parasympathetic tone (e.g., glaucoma, GI stasis, cardiac tachyarrhythmias).
Mechanism of action
Oxybutynin exerts its effects via a dual mechanism of action on the lower urinary tract:
- Antimuscarinic (atropine-like) effect: It competitively antagonizes acetylcholine at postganglionic muscarinic receptors. It has a high affinity for M1, M2, and M3 receptors, with M3 being the primary receptor mediating bladder detrusor contraction.
- Direct spasmolytic (papaverine-like) effect: It directly relaxes smooth muscle independent of its anticholinergic activity.
These combined actions → relaxation of the bladder detrusor muscle → increased maximum bladder capacity → decreased frequency and amplitude of uninhibited detrusor contractions → delayed initial desire to void.
Safety & warnings
Contraindications
- Obstructive GI tract disease
- Intestinal atony or paralytic ileus
- Angle closure glaucoma
- Hiatal hernia
- Cardiac disease (especially mitral stenosis, arrhythmias, tachycardia, CHF)
- Myasthenia gravis
- Hyperthyroidism
- Prostatic hypertrophy
- Severe ulcerative colitis
- Urinary retention or other obstructive uropathies
- Obstructive GI disease
- Gastrooesophageal reflux
- Obstructive urinary disease
Adverse effects
- Diarrhea
- Constipation
- Urinary retention
- Hypersalivation
- Sedation
- Dry mouth (xerostomia)
- Dry eyes (keratoconjunctivitis sicca)
- Tachycardia
- Anorexia
- Vomiting
- Weakness
- Mydriasis (pupil dilation)
- Diarrhoea
- Skin reactions
- Palpitations
- Confusion
Precautions
Use only when benefits outweigh risks in patients with GI obstruction, ileus, glaucoma, cardiac disease, myasthenia gravis, hyperthyroidism, prostatic hypertrophy, or urinary retention. Safety during pregnancy is not firmly established (FDA Category B); animal studies show no teratogenic effects. May inhibit lactation, though no documented problems in nursing offspring have been noted.
Drug interactions
May intensify oxybutynin's anticholinergic adverse effects.
May inhibit metabolism and increase oxybutynin systemic levels.
May exacerbate the sedating effects of oxybutynin.
May inhibit metabolism and increase oxybutynin systemic levels.
Additive anticholinergic side effects (e.g., severe constipation, urinary retention, tachycardia)
Potential CYP inhibition leading to increased oxybutynin plasma concentrations
Potential CYP inhibition leading to increased oxybutynin plasma concentrations
Monitoring
- Clinical efficacy (reduction in urinary incontinence or frequency)
- Adverse effects (signs of anticholinergic toxicity such as dry mouth, tachycardia, constipation, or urinary retention)
- Urinary output and frequency
- Heart rate
- Bowel movements (monitor for constipation)
- Signs of excessive sedation
Pharmacokinetics
Half-life
Absorption
Rapidly and well absorbed from the GI tract.
Distribution
Distributes into the brain, lungs, kidneys, and liver.
Metabolism
Metabolized in the liver.
Elimination
Excreted in the urine.
Overdose
Overdosage can lead to severe anticholinergic toxicity.
- CNS effects: Restlessness, excitement, seizures.
- Cardiovascular effects: Hypertension or hypotension, tachycardia, circulatory failure.
- Other signs: Fever, nausea, vomiting.
- Massive overdose: May lead to paralysis, coma, respiratory failure, and death.
Treatment: Consists of general techniques to limit GI absorption (e.g., emesis, activated charcoal) and supportive care. Intravenous physostigmine may be useful to reverse severe anticholinergic signs.
Available products
Formulations
- Oral tablets
- Oral extended-release tablets
- Oral syrup
- Transdermal patch
- Topical gel
- 2.5 mg tablet
- 3 mg tablet
- 5 mg modified-release tablet
- 10 mg modified-release tablet
- 2.5 mg/5 ml oral solution
Human-labeled
- Oxybutynin Chloride Oral Tablets: 5 mg
- Oxybutynin Chloride Oral Extended release tablets: 5 mg, 10 mg & 15 mg
- Oxybutynin Chloride Oral Syrup: 1 mg/mL
- Oxybutynin Chloride Transdermal System, Topical: 36 mg (delivering 3.9 mg/day)
- Oxybutynin Topical Gel: 10%
- Ditropan
- Lyrinel
- Oxybutynin generics
Regulatory status
POM (Prescription Only Medicine). Used under the cascade.
POM (Prescription Only Medicine). Used under the cascade.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Tablets and oral solution should be stored at room temperature in tight containers. Protect oral solution from light. Tablets have an expiration date of 4 years after manufacture.
Client information
Oxybutynin is used to help relax the bladder and reduce urinary leaking or spasms.
Important Notes for Pet Owners:
- Give exactly as prescribed. Do not change the dose without consulting your veterinarian.
- Watch for side effects: Because this drug dries up bodily secretions, your pet may experience a dry mouth (lip smacking, increased drinking) or dry eyes.
- Monitor bathroom habits: Contact your veterinarian if your pet develops constipation or seems to be straining to urinate without producing urine (urinary retention).
- Store the medication at room temperature and keep liquid forms protected from light.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.