Oxybutynin

What is oxybutynin?

Oxybutynin is a medication used to help stop bladder spasms that cause urine leakage (refractory urinary incontinence) in cats and dogs.

It is used off label (extra label) in veterinary medicine. Many drugs are commonly prescribed for off-label use in veterinary medicine. 

“Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How do I give my pet oxybutynin?

Oxybutynin comes in tablet and liquid syrup forms. Extended-release tablets are available.

• All forms are given orally (by mouth). 
• This medication can be given with or without food.
• Measure liquid forms of this medication very carefully.
• Give this medication exactly as prescribed and directed by your veterinarian.

This medication should start to take effect in 1–2 hours. 

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Oxybutynin may cause the following side effects:

• Diarrhea, constipation
• Not urinating often (urine retention)
• Drowsiness
• Drooling
• Lack of appetite, vomiting
• Dry eye or dry mouth

Serious adverse reactions may occur. If any of the following signs develop, stop giving oxybutynin and contact your veterinarian immediately:

• An allergic reaction such as irregular breathing, rash, fever, puffiness and swelling around the face
• Signs of urinary obstruction (persistent difficulty urinating, unable to urinate, racing heartbeat, pain, collapse)
• Seizures

Drug sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses, but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment. 

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, though effects may last longer in pets with kidney and/or liver disease.

Are there any risk factors for this medication?

DO NOT USE in animals who:

• Are allergic to any component of the medication

USE WITH CAUTION in animals who:

• Have an intestinal blockage
• Are unable to urinate
• Have heart disease, kidney disease, or prostatic disease
• Have myasthenia gravis, thyroid disease, or colitis

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with oxybutynin:

• Amantadine
• Anticholinergics (e.g., atropine, tricyclic antidepressants, antihistamines, etc.)
• Atenolol
• Azole antifungals (e.g., ketoconazole)
• Benzodiazepines (e.g., diazepam, midazolam)
• Central nervous system (CNS) depressants (e.g., methocarbamol, trazadone)
• Clarithromycin, erythromycin
• Opioids (e.g., buprenorphine, hydrocodone)

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is there any monitoring that needs to be done with this medication?

• Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects. 
• At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.

How do I store oxybutynin?

• Store at 68°F-77°F (20°C-25°C) protected from light and moisture; short excursions to 59°F-86°F (15°C-30°C) permitted.
• Keep medication out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.