What is oxybutynin, and how does it work (mechanism of action)?
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.
What brand names are available for oxybutynin?
Ditropan (discontinued brand in the US); Ditropan XL; Oxytrol; Anturol; Gelnique
Do I need a prescription for oxybutynin?
Yes
What are the side effects of oxybutynin?
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.
What is the dosage for oxybutynin?
- 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.
QUESTION
What is urinary incontinence?
See Answer
Which drugs or supplements interact with oxybutynin?
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.
Is oxybutynin safe to take if I’m pregnant or breastfeeding?
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 else should I know about oxybutynin?
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.