ClassIndications
Administration/Absorption- Oral
- Rapidly absorbed from gastrointestinal tract
Dosage
Distribution- 91-93% protein bound
- VOD 193 L
Mechanism- competitively antagonizes the M1, M2, and M3 subtypes of the muscarinic acetylcholine receptor
- exerts a direct antispasmodic effect on smooth muscle
- inhibits the
muscarinic action of acetylcholine on smooth muscle
- No blocking effects
occur at skeletal neuromuscular junctions or autonomic ganglia
(antinicotinic effects)
- By inhibiting particularily the M1 and M2
receptors of the bladder, detrusor activity is markedly decreased
Excretion- metabolized primarily by the cytochrome P450 enzyme systems
- particularly CYP3A4
- found mostly in the liver and gut wall
- Extensively metabolized by the liver, with less than 0.1% of the
administered dose excreted unchanged in the urine
Side effects- dry mouth
- over a quarter of patients who begin oxybutynin treatment may have to stop because of dry mouth
- difficulty in urination
- constipation
- blurred vision
- drowsiness and dizziness
- Calcium defects
- An intake of calcium
of 800 to 1000 mg is suggested
Interactions
Contraindications
- untreated angle closure glaucoma
- untreated narrow
anterior chamber angles
- partial or complete
obstruction of the gastrointestinal tract
- hiatal hernia
- gastroesophageal reflux disease
- paralytic ileus
- intestinal atony of the elderly or debilitated
patient
- toxic megacolon complicating ulcerative colitis
- severe colitis
- myasthenia gravis
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