Home' News Bulletin : ADA News Bulletin July 2016 Contents REGULAR I PHARMAADVICE
This month I have chosen to write about medicines used in
dementia partly because these drugs have side effects relevant to
oral health and partly to coincide with the ADA’s current focus on
quality dental care for people with dementia.
Just as there are many types of dementia, there are also many
types of medicines used to assist people with dementia. Some
medicines are aimed at treating the cognitive impairment and
others are used to manage the neuropsychiatric and behavioural
issues that often accompany the diagnosis. If you consider
the many medicines that may also be prescribed for chronic
conditions such as diabetes, arthritis and heart disease, you
can see that polypharmacy and drug interactions are constant
concerns in the care of dementia patients.
Due to limited space, I will only discuss the prescription drugs used
to treat dementia and the neuropsychiatric symptoms. We’ll have
to leave the myriad of complementary medicines and supplements
people use for dementia for another time.
WHAT ROLE DO DRUGS PLAY?
Over the past 20 years, prescription medicines have made a
significant difference to dementia management but overall drugs
only play a minor role. None of the medicines currently available for
dementia of any kind stop or reverse the course of the disease, but
they can marginally improve cognitive function and behaviour and
may slow progression. Quality care of dementia patients relies more
on non-pharmacological interventions, maintenance of physical
exercise and monitoring the patient’s general health especially
vascular risk factors to optimise health and independence.
DRUGS TO TREAT COGNITIVE DECLINE
Only four medicines are on the Australian market to treat dementia
and all are TGA-registered just for Alzheimer’s-type dementia.
Three of these medicines are cholinesterase inhibitors: donepezil
(Aricept®), rivastigmine (Exelon®), and galantamine (Reminyl®); and a
fourth drug is an N-methyl-d -aspartate (NMDA) receptor antagonist
called memantine (Ebixa®). The clinical efficacy of all four medicines
Patients must meet specific criteria to be eligible for
treatment with these medicines under the Pharmaceutical Benefits
Scheme. For those interested in pharmacognosy, the drug called
galantamine is a naturally-occurring alkaloid originally isolated from
several plants including snowdrops and daffodil bulbs.2
Cholinesterase inhibitors (ChEI’s) work by blocking the breakdown
of acetylcholine in the brain, which is known to be deficient in both
Alzheimer’s disease (AD) and dementia with Lewy Bodies (DLB).
ChEI’s are indicated for use in mild to moderate AD, and all are
formulated as oral dosage forms except rivastigmine which also
comes as a patch. As mentioned above, these drugs can provide
some symptomatic benefit to people in early Alzheimer’s and may
serve to slow down the rate of cognitive decline. There is also some
evidence they can improve mood and behavioural symptoms
For this reason, a trial of a ChEI targeting both cognitive
and neuropsychiatric symptoms in behaviourally dysregulated
AD patients makes sense before the addition of any psychotropic
There is no evidence that any ChEI is better than another
and many specialists switch from one to another when there is little
efficacy or poor tolerance of the first.
The main adverse effects of ChEI’s are gastrointestinal, as their action
of increasing acetylcholine, occurs in the gut as well as the brain,
particularly when the medicine is administered orally. The most
common adverse effects of ChEI’s are nausea, vomiting, diarrhoea,
loss of appetite and increased salivation.
Switching to rivastigmine
patches can help avoid some of these gastrointestinal side effects.
Other well documented effects include fainting and falls, insomnia,
nightmares, weight loss, bronchoconstriction (particularly in
patients with asthma), bradycardia and urinary incontinence.
Memantine (Ebixa®), the NMDA-receptor antagonist, is used to
treat moderate to severe AD and vascular dementia. It has been
shown to provide no benefit in early dementia and in AD is most
often used in combination with one of the three ChEI’s later in the
disease. Its mechanism of action is distinct from the cholinergic
agents in that it is claimed to be neuroprotective. The idea is
that cerebral ischaemia prompts excess stimulation of cortical
and hippocampal neurones (areas of learning and memory) by
the neurotransmitter glutamate, but blocking glutamate/NMDA
receptors may preserve these neurones.
Memantine is much better tolerated than the cholinergic agents.
Side effects tend to affect the central nervous system, with dizziness,
vertigo, somnolence and confusion the most commonly reported.
Memantine requires slow dose titration over a month to minimise
the adverse effects of agitation, hallucination, headache and
possibly seizures. Being renally excreted, memantine will accumulate
in people with renal impairment.
DRUGS TO TREAT NEUROPSYCHIATRIC
Neuropsychiatric complications of dementia appear universally
in all forms of dementia. They are a significant source of disability
and carer burden and can also sometimes elude appropriate
diagnosis and treatment. Symptoms experienced include psychosis,
hallucinations, aggression, agitation, disinhibition, depression,
anxiety and sleep disorders.
Nonpharmacological interventions are considered first-line therapy,
but SSRI antidepressants can help depression and donepezil and
memantine may reduce irritability and anxiety and lessen the
burden for caregivers.
Antipsychotic medicines are prescribed
Medicines used in dementia
What dentists should know
ADA NEWS BULLETIN | JULY 2016 | 29
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