Risperidone: uses, side effects and dementia warning

Risperidone affects dopamine and serotonin in the brain. The NHS lists four uses: schizophrenia, the symptoms of mania in bipolar disorder, aggressive or agitated behaviour in children over 5 and young people with conduct disorder or autism, and aggression or agitation in adults with Alzheimer's disease.

It manages symptoms but is not a cure, and it does not change personality or cause addiction.

Risperidone is made as tablets, melt-in-the-mouth tablets, a liquid and injections. The liquid is measured with the syringe or dropper supplied, never a kitchen spoon. Injections are given every 2 or 4 weeks, and are for schizophrenia only.

The NHS gives typical starting points. For schizophrenia in people aged 65 or under it is 2 mg daily, going up to 4 mg on day two, with a usual range of 4 to 6 mg. For mania it starts at 2 mg once a day. Over-65s begin on 0.5 mg twice a day. In Alzheimer's aggression the start is 0.25 mg twice daily. Doses for children depend on weight. Your prescriber sets your own dose.

Missed a dose? For once-daily use, take it if more than 12 hours remain until the next dose; for twice daily, more than 8 hours. Never double up.

The NHS says common side effects affect up to 1 in 10 people.

• Difficulty sleeping: take the medicine in the morning and avoid screens and alcohol before bed.

• Headaches, stomach pain, nausea, vomiting, constipation and diarrhoea, each with simple self-care advice.

• Weight gain or appetite changes: balanced meals, avoiding high-calorie snacks, regular exercise.

• Breast changes such as swelling, pain or milk leaking, which may reflect hormone changes.

Call NHS 111 for uncontrolled twitching, a swollen, painful or red leg, or muscle stiffness and difficulty moving. Call 999 or go to A&E for chest pain with breathing difficulty, stroke signs, high temperature with stiff muscles, sweating and anxiety, a fast heartbeat, seizures or a painful erection lasting several hours. Anaphylaxis needs 999.

Tell the prescriber about heart problems, low blood pressure, a past stroke or high stroke risk, movement problems of the tongue, mouth or face, Parkinson's disease or dementia, low white blood cells, diabetes, epilepsy, prolonged erections, temperature regulation problems, kidney or liver impairment and blood clots.

The NHS lists rifampicin, carbamazepine, phenytoin, itraconazole, benzodiazepines, opioid painkillers, sedating antihistamines, medicines that slow the heart, blood pressure medicines, levodopa, methylphenidate and diuretics such as furosemide. Avoid St John's wort and ginkgo biloba, which can reduce its effect or increase side effects.

The NHS says risperidone can be taken in pregnancy despite limited data, because the risk of stopping is thought to exceed any risk to the baby. Only very small amounts reach breast milk. Do not share a bed with your baby while taking it.

Keep taking it even if you feel better and never stop without talking to your doctor. Limit alcohol and avoid driving if sleepy. Report suspected side effects to the MHRA Yellow Card scheme.