Oxybutynin, sold under the brand name Ditropan among others, is an anticholinergic medication primarily used to treat overactive bladder. It is widely considered a first-line therapy for overactive bladder due to its well-studied side effect profile, broad applicability, and continued efficacy over long periods of time. It works similar to tolterodine, darifenacin, and solifenacin, although it is usually preferred over these medications. It is sometimes used off-label for treatment of hyperhidrosis, or excessive sweating. It has also been used off-label to treat bedwetting in children, but this use has declined, as it is most likely ineffective in this role. It is taken by mouth or applied to the skin.

Common side effects include dry mouth, constipation, dizziness, trouble sleeping, and urinary tract infections. Serious side effects may include urinary retention and an increased risk of heat stroke. Use in pregnancy appears safe but has not been well studied while use in breastfeeding is of unclear safety. It is an antimuscarinic and works by blocking the effects of acetylcholine on smooth muscle.

Oxybutynin was approved for medical use in the US in 1975. It is available as a generic medication. In 2023, it was the 114th most commonly prescribed medication in the United States, with more than 5 million prescriptions.

Oxybutynin is used in the form of instant-release capsules, extended-release capsules, or transdermal products. All of these are considered safe and effective options for treatment of detrusor muscle-mediated overactive bladder. Extended-release formulations decrease the number of weekly incontinence episodes by an average of 90% compared to an untreated state. Some studies have identified advantages of transdermal oxybutynin over capsules, finding decreased frequency of incontinence episodes and increased average voided volume of urine.

Oxybutynin has been established through head-to-head trials as a more effective for overactive bladder than tolterodine, another anticholinergic medication. Specifically, the extended-release form of oxybutynin was found to have greater effect in both the short- and long-term. However, oxybutynin is not selective for the bladder like tolterodine, and thus has a wider range of side effects. Tolterodine and other anticholinergics are primarily used when clinicians and patients want to reduce the side effect profile.

Because both drugs have been studied extensively and shown relatively high efficacy, both oxybutynin and tolterodine are considered first-line treatments for overactive bladder. They are thus the typical choices for initial treatment of the condition. The choice of initial therapy often comes down to whether a patient prefers somewhat higher efficacy (oxybutynin) or somewhat reduced side effects (tolterodine).

Since the 2010s, oxybutynin has increasingly been used to treat hyperhidrosis (excessive sweating). Numerous studies have identified concrete benefits of the drug in treating this condition, but have not identified appropriate dosing or the full spectrum of possible side effects, although dry mouth is seemingly infrequent in patients with hyperhidrosis. Until further clinical trials can be conducted, oxybutynin is only used as an off-label medication for hyperhidrosis (as of 2024).

Common adverse effects that are associated with oxybutynin and other anticholinergics include: dry mouth, difficulty in urination, constipation, blurred vision, drowsiness, and dizziness. Anticholinergics have also been known to induce delirium.