Dr Sharon Rees @reesprescribe
Day 1: A derivative of the antiviral drug amantadine, #memantine was first synthesised in the 1960s. The antiviral action (of both drugs) remains unclear & neither is recommended for use as an anti-viral agent. However, #memantine is known to be effective for Alzheimer's disease (AD) and was licensed in Europe in 2013.
Dr Sharon Rees @reesprescribe
#memantine is used 2nd line for moderate-severe Alzheimer's disease usual maintenance 20 mg/day; tablet or oral solution. Can be an alternative to acetylcholinesterase inhibitors (AChIs); #memantine can also be added to the AChI (combination may have additive effect but poor evidence).
Dr Sharon Rees @reesprescribe
Kinetics; #memantine is 100% bioavailable post oral absorption! Minor metabolism possible via phase 2. 99% renal excretion therefore care in renal impairment (if severe halve the dose). Active tubular reabsorption occurs, which is enhanced by increased pH, so diet or antacids can affect clearance. T½ 2-4 days.
Dr Sharon Rees @reesprescribe
Day 4: MOA: #memantine is a non-competitive NMDA antagonist, whereby it preferentially blocks overactive ion channels (this may be what leads to Alzheimer's disease symptoms). By allowing physiological glutamate signalling, while reducing excitability, some neurological functions are restored, such as memory.
Dr Sharon Rees @reesprescribe
Day 5: Adverse drug events for #memantine: Common; psychiatric disorders, somnolence, constipation, liver conditions, headache, impaired balance, dyspnoea. Rare/serious ADRs include VTE, fungal infection, pancreatitis, seizure (not exhaustive).
Dr Sharon Rees @reesprescribe
Day 6: Drug-drug interactions #memantine; CNS toxicity with concurrent amantadine/ketamine (severe). Can increase effects of levodopa (and other Parkinson's disease drugs [moderate]) and can increase effects of anti-muscarinics; May increase the anti-coagulant effect of warfarin (in SPC and CKS, but not BNF). Not exhaustive.
Dr Sharon Rees @reesprescribe
Day 7: Neurodegeneration in Alzheimer's disease is possibly caused by dysregulation of calcium, increased production of beta amyloid, leading to cell death. Suppressing excessive glutamate signalling via #memantine could inhibit this pathological process, and may slow down disease progression (still poorly understood).
EARN YOUR CPD CERTIFICATE
With the help of Prescribing and Therapeutics Training Ltd and the Journal of Prescribing Practice, you can earn your 1-hour CPD certificate
Complete the additional reading suggested below and then answer the ten questions. Please submit the answers to reesprescribe@gmail.com as a numbered list with TRUE/FALSE or the correct A, B, C, D option. If you achieve 8 or more out of ten on the questions, a CPD certificate will be emailed to you.
Further reading on #memantine
- Dementia: https://bnf.nice.org.uk/treatment-summary/dementia.html
- Memantine hydrochloride: https://fg.bmj.com/content/flgastro/9/1/10.full.pdf
- Memantine Mylan 10 mg film-coated tablets:https://www.medicines.org.uk/emc/product/716/smpc#gref
Memantine is a drug related to levodopa
TRUE or FALSE?
Memantine is used in the UK for Alzheimer's disease, but not for Parkinson's disease
TRUE or FALSE?
Which of the following is TRUE?
- Memantine has poor oral absorption
- Memantine has some anti-viral action(s)
- Memantine undergoes extensive phase 1 metabolism in the kidney
- Memantine has a short half-life
Memantine is used on its own and shouldn't be added to other drugs used for Alzheimer's disease
TRUE or FALSE
Memantine is usually used second line as a treatment for AD
TRUE or FALSE
Which best describes the mechanism of action for memantine?
- It enhances dopamine signalling
- It restores memory by encouraging re-growth of neurons in the amygdala
- It calms neuro-excitability by blocking NDMA (glutamate) signal transmission
- It improves serotonin levels, which helps reduce stress and improve mood
Which is a common adverse drug reaction for memantine?
- Constipation
- Seizure
- VTE
- Pancreatitis
Ketamine is also an NMDA antagonist and if used together with memantine, CNS toxicity can result
TRUE or FALSE?
Memantine blocks all glutamate signalling
TRUE or FALSE?
It is hoped that memantine can slow down Alzheimer's disease progression, but the clinical evidence for this is weak
TRUE or FALSE?