From the Guidelines
Oxybutynin works by suppressing detrusor overactivity.
Mechanism of Action
- Oxybutynin is an antimuscarinic medication that decreases detrusor overactivity in patients with neurogenic bladder 1.
- The medication relaxes the bladder muscle by blocking the action of acetylcholine, a neurotransmitter that stimulates bladder contractions 1.
- By reducing detrusor overactivity, oxybutynin helps to increase bladder capacity and reduce symptoms of urinary incontinence.
Dosage and Administration
- The typical dose of oxybutynin is 0.2 mg/kg orally given 3 times daily for subjects with a hostile bladder on urodynamic evaluation 1.
- In children with enuresis, the usual dose is 5 mg oxybutynin at bedtime, which may need to be doubled if necessary 1.
Important Considerations
- Oxybutynin should only be used after nonpharmacological methods to decrease detrusor overactivity have been tried, such as instituting sound, regular voiding habits 1.
- The medication can cause constipation and post-void residual urine, which may increase the risk of urinary tract infections 1.
From the FDA Drug Label
Oxybutynin chloride exerts a direct antispasmodic effect on smooth muscle and inhibits the muscarinic action of acetylcholine on smooth muscle. The mechanism of action of oxybutynin is through its antispasmodic and antimuscarinic effects, which help to relax bladder smooth muscle and decrease urgency and frequency of urination 2.
- Key effects:
- Direct antispasmodic effect on smooth muscle
- Inhibition of muscarinic action of acetylcholine on smooth muscle
- Relaxation of bladder smooth muscle
- Decrease in urgency and frequency of urination
From the Research
Mechanism of Action of Oxybutynin
The mechanism of action of oxybutynin involves several key aspects:
- Oxybutynin inhibits contraction of the detrusor muscle in the overactive bladder by binding to muscarinic M(3) receptors and blocking acetylcholinergic activation 3.
- It has both an antimuscarinic and a direct muscle relaxant effect, and, in addition, local anesthetic actions 4.
- Oxybutynin possesses anticholinergic and spasmolytic properties, which together form the basis for its use as a therapeutic option in patients with overactive detrusor function 5.
- The drug may elicit its effects via mechanisms other than direct inhibition of detrusor contraction, such as modifying afferent pathways in the mucosal region 6.
Key Findings
- Oxybutynin undergoes extensive first-pass metabolism to its active metabolite, N-desethyloxybutynin 3, 4, 7.
- The transdermal route of administration avoids the extensive first-pass metabolism of oxybutynin 3.
- Oxybutynin has a well-documented efficacy in the treatment of detrusor overactivity, and is a drug of first choice in patients with this disorder 4, 5.
- The drug's metabolic fate involves not only N-deethylation but also N-oxidation, followed by rearrangement to enaminoketone 7.