Memantine: Alzheimer's medicine uses and cautions

Memantine is prescribed for people with moderate to severe Alzheimer's disease. The NHS is careful to say that it does not cure the condition but can help with its symptoms. It is a prescription-only medicine.

It is often discussed alongside donepezil, but the two are different types of medicine and are used at different points. A specialist decides which, if either, suits the stage of illness.

Glutamate is a chemical messenger in the brain, and in Alzheimer's disease the NHS says there can be too much of it. Memantine reduces those effects by blocking glutamate, which helps protect brain cells affected by the disease.

The NHS page does not state how long it takes to take effect, so there is no quoted timescale to rely on. Review appointments are where benefit is judged.

Memantine comes as tablets swallowed whole, a liquid taken with water and orodispersible tablets that dissolve on the tongue. It is taken once a day at the same time each day, with or without food.

The NHS says the doctor may prescribe a low dose to begin with and increase it each week for a few weeks, to reduce side effects. No fixed dose is given on the page, so follow the schedule on your own label.

If a dose is missed, skip it and take the next at the usual time, never doubling up. An extra dose is unlikely to cause problems, but a pharmacist or NHS 111 should be asked; if an overdose was intentional, use 111 rather than the pharmacist.

Common effects listed by the NHS are headaches, dizziness, balance problems, shortness of breath, drowsiness, constipation and raised blood pressure. If you are dizzy or sleepy, do not drive; the doctor can advise on driving for your situation.

Rare serious effects include blood clots leading to heart attack or stroke, inflammation of the liver or pancreas, anaphylaxis and suicidal thoughts. For carers, a sudden change in behaviour or mood is worth reporting quickly. Suspected side effects can be reported through Yellow Card.

The NHS lists several reasons memantine may be unsuitable, so the prescriber will want a full history.

• An allergic reaction to memantine.

• Epilepsy.

• A previous heart attack, or heart failure.

• Uncontrolled high blood pressure.

• Severe kidney problems.

• Severe urinary tract infections.

The NHS says memantine should not be combined with certain Parkinson's medicines, namely amantadine and apomorphine, nor with medicines for restless legs syndrome (ropinirole, pramipexole, rotigotine) or with cabergoline. This matters in practice because people with dementia and Parkinson's symptoms may be on several of these at once.

No alcohol restriction is given on the NHS page.

The NHS says memantine is not usually used in pregnancy and not usually recommended when breastfeeding, although a doctor may recommend it if benefits outweigh risks. This is rarely relevant but is stated for completeness.

The NHS says doctors may suggest you keep taking it for as long as it helps your symptoms, with regular reviews to check. Any decision to stop is made with the prescriber, not alone.