Oxybutynin: tablets, liquid and patches for the bladder

Oxybutynin treats the symptoms of an overactive bladder: a sudden, urgent need to pass urine, needing to go more often and urinary incontinence. It also treats bedwetting in children.

It is only available on prescription in the UK. Brand names are Aspire, Ditropan and Kentera. It works by relaxing the bladder muscle so the bladder holds more liquid, which means you need to pass urine less often and less urgently.

The NHS lists standard tablets of 2.5 mg or 5 mg, slow-release tablets of 5 mg or 10 mg, a liquid of 2.5 mg or 5 mg per 5 ml, and 3.9 mg patches. Adults and children aged 12 and over usually take 5 mg two or three times a day, up to a maximum of 5 mg four times a day, with lower doses typical in people over 65. Children aged 5 to 11 start at 2.5 mg two or three times a day. Slow-release tablets are usually 5 mg once daily, and a patch is applied twice weekly, every 3 to 4 days. Your prescriber chooses the form and dose.

Swallow standard and slow-release tablets whole with water, never chewing or crushing the slow-release type. Measure liquid with the supplied syringe or spoon, not a kitchen teaspoon. Patches go on clean, dry skin on the stomach, hip or bottom.

• Twice-daily doses should be about 12 hours apart; three or four doses should be spread evenly.

• Missed a dose? Take it when you remember unless the next is almost due. Never double up.

• Overdose can cause hallucinations, restlessness, dilated pupils and difficulty passing urine; call 999 for a fast or irregular heartbeat, breathing problems or loss of consciousness.

Most adults and children aged 5 and over can take oxybutynin, but the list of conditions needing discussion is long. It includes previous allergic reactions, myasthenia gravis, dementia or cognitive impairment, autonomic neuropathy, acute angle closure glaucoma, difficulty urinating or an enlarged prostate, a range of heart conditions (including heart failure, long QT syndrome and irregular or very fast or slow heartbeats), thyroid, kidney and liver problems, and digestive conditions such as severe constipation, hiatus hernia, heartburn or toxic megacolon. Tell your doctor too if you are pregnant, planning pregnancy or breastfeeding.

Common effects are dry mouth, headache, dizziness, sleepiness or vertigo, diarrhoea, vomiting, constipation, wind or burping, stomach pain, dry eyes, blurred vision and difficulty passing urine. Practical steps include sugar-free sweets for dry mouth, fibre and water for constipation, eye drops for dry eyes, and not driving with blurred or sleepy symptoms.

Call NHS 111 for severe constipation or being unable to open the bowels, difficulty emptying the bladder, signs of a severe urine infection such as fever, burning and bloody or cloudy urine, or swollen ankles or legs. Call 999 if you overheat without sweating normally, especially in hot weather or with a high fever, or if you have signs of anaphylaxis.

Suspected side effects can be reported through the Yellow Card scheme.

The NHS advises not taking oxybutynin for longer than necessary. A doctor reviews it after 4 weeks and then every 6 to 12 months, partly because of a possible increased risk of confusion and of dementia getting worse in some people. For anyone with memory problems, that balance is a matter for the prescriber.

Pelvic floor muscle training, bladder training and cutting down on caffeine and fluids are listed as non-drug options worth discussing.

Oxybutynin may occasionally be used in pregnancy when bladder symptoms are severe and cannot be controlled otherwise. It is safe to use while breastfeeding after medical advice, since the amount in milk is likely to be tiny. There is no evidence it reduces fertility.

The NHS lists medicines that can add to its effects, including amantadine and levodopa, phenothiazines, clozapine, haloperidol, donepezil, rivastigmine and galantamine, amitriptyline, imipramine and dosulepin, sedatives, prochlorperazine, domperidone and metoclopramide, digoxin, quinidine, disopyramide, dipyridamole, chlorphenamine, diphenhydramine and macrolide antibiotics such as erythromycin. Paracetamol is safe to take with it.

Avoid alcohol when starting oxybutynin or raising the dose, because the combination causes heavy drowsiness, and alcohol may increase night-time toilet trips. Do not drive, cycle or use tools if it makes you sleepy, blurs your vision or leaves you dizzy. You can eat normally, but less caffeine from tea, coffee and cola may help.