AChE inhibitors are licensed for the symptomatic treatment of mild to moderate AD. Between 40 and 70 per cent of people with AD benefit from treatment. However, in most cases, the benefits are temporary.

Donepezil

Donepezil was the first oral AChE inhibitor to receive a product licence and is available as tablets or orodispersible tablets. Treatment usually takes place in the evening, unless this causes insomnia. The starting dose of 5mg once daily should be maintained for one month. The dose can be increased to a maximum of 10mg if necessary.

The most common adverse effects include nausea, vomiting, anorexia, diarrhoea, fatigue, insomnia, headache, dizziness, fainting, abnormal dreams, hallucinations, agitation, aggression, muscle cramps and urinary incontinence. These are generally mild and normally disappear within a few days.

Donepezil has been linked to an increased risk of gastrointestinal (GI) problems. Patients with a history of ulcers, or those taking NSAIDs, should be monitored carefully. Due to their pharmacological action, AChE inhibitors may cause reduced heart rate or bradycardia. This is concerning for patients with supraventricular cardiac conduction conditions. Donepezil should be used with caution in patients with mild to moderate hepatic impairment.

Rivastigmine

Rivastigmine is available as tablets, an oral solution or transdermal patches. The oral starting dose is 1.5mg twice daily with meals, increasing by 1.5mg at minimum intervals of two weeks, if well tolerated.

The patches are applied once every 24 hours. These may cause reduced GI adverse effects and could be beneficial for patients with swallowing difficulties. The most common adverse effects include drowsiness, nausea, vomiting, abdominal pain, indigestion and diarrhoea, which often occur when the dose is increased. If GI adverse reactions or movement disorders (e.g. tremors) occur in patients with Parkinson's disease, the dose may be reduced. If adverse reactions persist, the daily dose should be discontinued or temporarily reduced to the previous well-tolerated amount.

Other side effects include anorexia, weight loss, GI bleeding, headache, insomnia, sweating, dizziness, fainting, salivation, tremor, worsening of Parkinson's disease, bladder outflow obstruction and urinary incontinence.

Galantamine

Galantamine is available as tablets or an oral solution. The starting dose is 4mg twice daily with meals, increasing at four weekly intervals up to a maximum of 12mg. Modified release capsules are also available, with a starting dose of 8mg once daily, increasing at four weekly intervals to a maximum of 24mg.

Common adverse reactions include nausea and vomiting. Other adverse effects include diarrhoea, abdominal pain, indigestion, anorexia, weight loss, fatigue, dizziness, fainting, headache, drowsiness and sleepiness. These generally last for less than a week. Confusion, insomnia, tremors, depression, hallucinations, muscle spasm, and bradycardia may also occur. Galantamine should be used with caution in moderate to severe hepatic impairment and is contraindicated in severe renal impairment.