oxybutynin

Oxybutynin is an oral drug that is used for treating urinary bladder spasm. 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 bladder's muscle cells. Oxybutynin suppresses involuntary contractions of the bladder's smooth muscle (spasms) by blocking the release of acetylcholine. This is referred to as an "anticholinergic effect." Oxybutynin also directly relaxes the bladder's outer layer of muscle (the detrusor muscle). The FDA approved oxybutynin in July 1975.

Ditropan (discontinued brand in the US); Ditropan XL; Oxytrol; Anturol; Gelnique

Yes

The most common side effects of oxybutynin are dry mouth, constipation, tiredness, and headache. About 1 in every 14 patients taking oxybutynin tablets cannot tolerate it because of side effects. Diarrhea, urinary tract infections, blurred vision, and difficulty urinating also may occur. The transdermal patch or gel may also cause local reactions at the application sites such as itching and rash. Transdermal patches or gel cause fewer side effects than the tablets. Serious hypersensitivity reactions involving swelling of the throat, lips, and tongue also may occur.

• The usual dose of immediate-release oxybutynin is 5 mg 2 to 3 times daily. Elderly patients sometimes start with a lower dose of 2.5 mg.
• The recommended dose using extended-release tablets is 5 to 10 mg once daily not to exceed 30 mg 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 patch is applied twice weekly (every 3 to 4 days). 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.
• One sachet of the 10% gel or three pumps of the 3% gel should be applied to intact skin of the abdomen, upper arm, shoulder or thighs. Application sites should be rotated. Patients should wash hands immediately after applying the gel in order to avoid transferring oxybutynin to other parts of the body or other individuals.

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 which include 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, including diphenhydramine (Benadryl), dimenhydrinate (Dramamine), scopolamine (Trans-Scop), benztropine (Cogentin), disopyramide (Norpace), thioridazine (Mellaril), and amitriptyline (Elavil, Endep).

Combining pramlintide (Symlin) with oxybutynin may severely reduce bowel movements. This combination should be avoided.

Oxybutynin may delay passage of potassium tablets through the digestive system and result in ulceration or narrowing of the small intestine.

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.

It is not known if oxybutynin is excreted in human milk.

What preparations of oxybutynin are available?

Tablets (immediate release): 5 mg; Tablets (extended release): 5, 10, and 15 mg; Transdermal delivery system or patch: 3.9 mg/day; Syrup: 5 mg/5 ml. Transdermal Gel: 3% or 10%.

How should I keep oxybutynin stored?

Oxybutynin should be stored at room temperature, 15 C to 30 C (59 F to 86 F). It should be kept out of the reach of children.