Oxybutynin is a competitive muscarinic acetylcholine receptor antagonist used primarily for the treatment of overactive bladder (OAB) syndrome. It acts as an antispasmodic on smooth muscle, reducing bladder contractility and increasing bladder capacity. The 5mg strength is a standard immediate-release oral tablet formulation widely used in the Indian clinical setting.
Adult: Initial dose: 5 mg orally two to three times daily. Maximum: 5 mg four times daily (20 mg/day). Dose titration should be based on response and tolerability.
Note: Tablet can be taken with or without food. Swallow whole with a glass of water. Taking with food may minimize GI upset. Maintain adequate fluid intake unless contraindicated.
Oxybutynin competitively antagonizes the binding of acetylcholine to muscarinic receptors (M1, M2, M3) on detrusor smooth muscle and other effector sites. In the bladder, this inhibition reduces involuntary detrusor muscle contractions, increases bladder capacity, and delays the initial desire to void.
Pregnancy: Category B: Animal studies have not shown risk, but no adequate, well-controlled studies in pregnant women. Use only if clearly needed and benefit justifies potential risk.
Driving: May cause dizziness, blurred vision, drowsiness, or impaired judgment. Patients should not drive or operate machinery until they know how the medicine affects them.
| Other Anticholinergics (e.g., Atropine, Dicyclomine, TCAs, Antipsychotics) | Additive anticholinergic effects (dry mouth, constipation, urinary retention, confusion, tachycardia). | Major |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Clarithromycin, Ritonavir) | Increased plasma levels of oxybutynin, leading to enhanced effects and toxicity. | Major |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | Decreased plasma levels of oxybutynin, potentially reducing efficacy. | Moderate |
| Opioid Analgesics | Increased risk of severe constipation and urinary retention. | Moderate |
| Potassium Chloride (wax-matrix tablets) | Increased risk of GI mucosal lesions due to reduced GI motility. | Moderate |
| Metoclopramide | Oxybutynin may antagonize the prokinetic effect of metoclopramide. | Moderate |
| Alcohol, CNS Depressants (Benzodiazepines, Opioids) | Additive sedative effects, impaired alertness. | Moderate |
Same composition (Oxybutynin (5mg)), different brands: