Flavoxate
Flavoxate is a urinary antispasmodic used primarily as an alternative treatment for **detrusor hyperspasticity** (hyperactive bladder or urge incontinence) in dogs. * It is particularly useful in refractory cases where standard therapies like **phenylpropanolamine (PPA)** alone have failed to achieve continence. * > **Clinical Pearl:** While not commonly used in veterinary medicine due to limited pharmacokinetic data, its dual action as a smooth muscle relaxant and antimuscarinic makes it a valuable second-line or adjunctive agent for urge incontinence.
Mechanism: Flavoxate exerts its effects through two primary mechanisms: * **Direct Smooth Muscle Relaxation**: It acts directly on the smooth muscle of the urinary tract, reducing spasms and increasing bladder capacity. * **Antimuscarinic Activity**: It competitively antagonizes **muscarinic acetylcholine receptors** in the detrusor muscle → inhibits parasympathetic nerve impulses → reduces involuntary bladder contractions. Unlike pure anticholinergics, its direct musculotropic effect provides targeted relief of urinary tract spasms.
Dosing by species
- To decrease urinary bladder contractility · 100-200 mg (per dog) · PO · q6-8h
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Pyloric or duodenal obstruction
- Obstructive intestinal lesions or ileus
- Achalasia
- Gastrointestinal hemorrhage
- Obstructive uropathies of the lower urinary tract
Adverse effects
- Weakness
- Gastrointestinal upset
- Changes in activity level
Drug interactions
- Anticholinergic drugs · Concomitant use may cause additive anticholinergic effects.
Monitoring
- Clinical efficacy (improvement in continence)
- Adverse effects (especially weakness and GI signs)
- Occasional CBCs (to monitor for neutropenia if used chronically)
- Creatinine (to monitor for renal dysfunction if used chronically)
Overdose
The approximate oral LD-50 for rats and mice are 4300 mg/kg and 1800 mg/kg respectively. While it has a wide margin of safety, massive overdose would likely result in severe anticholinergic signs (e.g., dry mouth, tachycardia, urinary retention, GI stasis). Treatment should be supportive and symptomatic.
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.