Dosage/Direction for Use
Oral Overactive bladder Adult: 2.5-5 mg bid-tid. May be increased to max 5 mg 4 times daily if necessary. As extended-release preparation: Initially, 5 mg once daily increased by 5 mg every wk if necessary to max 30 mg daily. Child: >7 yr for nocturnal enuresis: 2.5-3 mg bid increased if necessary to 5 mg bid-tid. Last dose should be given before bedtime. As extended-release preparation: 5 mg once daily, increased by 5 mg wkly if necessary to max 20 mg daily. Elderly: Initially, 2.5-3 mg bid increased to 5 mg bid if necessary. Oral Neurogenic bladder disorders Child: >5 years As immediate-release tab: 5 mg bid up to tid. As extended-release tab: 5 mg once daily. May increased to Max 15 mg once daily in 5 mg daily increments. Transdermal Overactive bladder Adult: 1 transdermal system (delivering 3.9 mg per day) applied to dry, intact skin on the abdomen, hip, or buttock twice wkly. |
Administration
May be taken with or without food.
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Contraindications
GI obstruction or atrophy, severe toxic megacolon, significant bladder outflow obstruction, glaucoma, urinary retention.
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Special Precautions
Elderly; hepatic or renal impairment; neuropathy; hyperthyroidism; prostatic hyperplasia; hiatus hernia; cardiac disease, reflux oesophagitis, ulcerative colitis, myasthenia gravis; pregnancy and lactation. High environmental temperature might cause heat prostration (fever with heat stroke due to decreased sweating).
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Adverse Reactions
Dry mouth, constipation, nausea, abdominal pain; blurred vision; headache, dizziness, drowsiness; dry skin, rash; photosensitivity, diarrhoea, insomnia, palpitation, weakness, dry eyes, confusion, hypertension, UTI, dyspepsia.
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Overdosage
Anticholinergic effects including CNS excitation (e.g. restlessness, tremor, irritability, convulsions, delirium, hallucinations), flushing, fever, dehydration, cardiac arrhythmia, vomiting, and urinary retention may occur after overdose. Treatment should be symptomatic and supportive. Activated charcoal may be administered.
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Drug Interactions
Co-administration with other anticholinergic drugs may cause undesirable increased anticholinergic effects. Additive sedation with CNS depressants and alcohol. Concentration may be increased by CYP3A4 inhibitirs (e.g. imidazole antifungals, macrolide antibiotics).
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Action
Oxybutynin exerts direct antispasmodic effect on the smooth muscle by inhibiting the muscarinic action of acetylcholine. It exhibits moderate anticholinergic effect, but has potent antispasmodic effects on urinary smooth muscle.
Absorption: Peak plasma concentrations after 1 hr. Distribution: Crosses the blood-brain barrier; enters breast milk. Metabolism: Hepatic: Undergoes first-pass metabolism. Excretion: Excreted in urine and faeces as metabolites. Elimination half life 2-3 hr. |
Storage
Oral: Store at 15-30°C (59-86°F). Transdermal: Store at 15-30°C (59-86°F).
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CIMS Class
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ATC Classification
G04BD04 - oxybutynin ; Belongs to the class of urinary antispasmodics.
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