Pharmacy Author: Emmanuel Saltiel, Pharm. D.
Medical Editor: Jay Marks, M.D.

GENERIC NAME: oxybutynin

BRAND NAME: Ditropan; Ditropan XL; Oxytrol

DRUG CLASS AND MECHANISM: Oxybutynin is a drug for treating bladder spasms.

Oxybutynin has a dual mechanism of action. Contraction of the smooth muscle of the bladder is stimulated by the release of acetylcholine by the nerves within the bladder and the attachment of the acetylcholine to receptors on the surface of the muscle cells. Oxybutynin suppresses involuntary contractions of the bladder's smooth muscle (spasms) by blocking the release of acetylcholine. This is called an “anticholinergic effect.” Oxybutynin also directly relaxes the bladder's outer layer of muscle (the detrusor muscle).

GENERIC: Yes (Immediate-release tablets only)

PRESCRIPTION: Yes

PREPARATIONS: Oxybutynin is available as 5 mg tablets. It is available in an extended release form as 5, 10, and 15 mg tablets and as a transdermal delivery system or patch (Oxytrol) providing 3.9 mg/day of oxybutynin. A liquid preparation also is available as oxybutynin chloride syrup, 5 mg/5 ml.

STORAGE: Oxybutynin should be stored at room temperature, 15-30°C (59-86°F). All medicines should be kept out of the reach of children.

PRESCRIBED FOR: Oxybutynin is used for adults with symptoms of overactive bladders that including sudden urges to urinate (urgency), urinary incontinence (the inability to control urination), and frequent urination. It also is used in children, aged 6 years and older, with symptoms of detrusor muscle hyperactivity associated with neurological conditions, such as spina bifida.

DOSING: The usual dose of immediate-release oxybutynin is 5 mg two to four times daily. Elderly patients sometimes start with a lower dose of 2.5 mg. The extended-release tablets are taken once daily. The oral forms can be taken with or without food. The extended release tablets must not be chewed, crushed, or broken. The tablet shell is not absorbed and is eliminated in the feces. The oxybutynin patch is applied twice weekly. The patch should be applied to dry, intact skin on the abdomen, hip, or buttock. A different application site should be used with each new patch, avoiding re-application to the same site within 7 days.

DRUG INTERACTIONS: The use of oxybutynin in patients who are receiving other drugs with anticholinergic effects will likely result in an increased frequency and/or severity of anticholinergic side effects. Such effects include dry mouth, constipation, confusion, blurred vision, urinary retention (the inability to urinate) and an increased heart rate or palpitations. There are many such drugs. A few include: diphenhydramine (Benadryl), dimenhydrinate (Dramamine), scopolamine (Trans-Scop), benztropine (Cogentin), disopyramide (Norpace), thioridazine (Mellaril), and amitriptyline (Elavil).

PREGNANCY: Studies of oxybutynin in pregnant rabbits, rats, and mice have not produced any evidence of harm in the fetus; however, since no controlled studies have been done in pregnant women, the potential benefit of this medicine needs to be weighed against any theoretical harm.

NURSING MOTHERS: It is not known if oxybutynin is excreted in human milk.

SIDE EFFECTS: The most common side effects of oxybutynin are dry mouth (3 out of every 5 or 60% of patients), constipation (1out of every 6 patients), tiredness (1 out of every 8 patients), and headache (1 out of every 10 patients). About 1 in every 14 patients taking oxybutynin cannot tolerate it because of side effects.

From the Doctors at MedicineNet.com

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