HNNS L54 - Drugs for Neurodegenerative Diseases Flashcards
Drugs for Parkinson’s disease
Increasing dopamine activity in the nigrostriatal system
- Dopamine precursors: levodopa (L-dopa) Dopamine cannot cross BBB
- Peripheral DOPA decarboxylase inhibitors: carbidopa, benserazide
- Dopaminergic agonists
1. Ergot derivatives: bromocriptine, pergolide
2. Non-ergot derivatives: ropinirole, pramipexole, rotigotine - MAO-B inhibitors, e.g. selegiline, rasagiline
- COMT inhibitors, e.g. entacapone, tolcapone
- Dopamine facilitator: amantadine
Reducing muscarinic cholinergic activity in the striatum
- Central anticholinergics, e.g. benztropine, benzhexol
Dopamine precursor for Parkinson’s Disease
Levodopa (L-dopa)
- Readily transported into CNS, converted to dopamine in brain by DOPA decarboxylase
High therapeutic index: drug of choice for symptom control esp in elderly
Side effects of L-dopa
Due to conversion of L-dopa to dopamine in the periphery
- Nausea, vomiting
- Arrhythmia
- Postural (orthostatic) hypotension
Due to overstimulation of central dopamine receptors
- Dyskinesia
- Hallucinations
- Restlessness
- Confusion
Do not use levodopa with…
- Nonselective MAO inhibitor, e.g. phenelzine Excess dopamine in periphery Converted into adrenaline, NA Life-threatening hypertensive crisis - Pyridoxine (Vitamin B6) Co-factor for the enzyme ↑peripheral breakdown of L-dopa - Anti-psychotics Block dopamine receptors Cause Parkinsonian-like symptoms
Peripheral DOPA decarboxylase inhibitor
Carbidopa
Benserazide
Does NOT cross BBB
- Reduce metabolism of dopamine in periphery
- Increase availability of dopamine to CNS
Dopamine receptor agonists for Parkinson’s
Bromocriptine (Ergot, D2 agonist)
Pergolide (Ergot, D1 and D2 agonist)
Pramipexole
Ropinirole
(non-ergot, D2 agonist, 1st line for younger patients)
Rotigotine (Non-ergot, D2 agonist, transdermal patches)
Bromocriptine
Ergot dopamine D2 agoinist
Useful to delay use of L-dopa in younger patients
In conjunction with L-dopa / carbidopa
- Relieve rigidity and tremor
Minimal effects on bradykinesia
Side effects:
- Hallucination, delirium
- Nausea, vomiting
- Cardiac arrhythmia, postural hypotension
- Erythromelalgia: red, painful and swollen feet or hands
Pergolide
Ergot derivative
Dopamine agonist at D1 and D2 receptors
In combination with L-dopa / carbidopa and anticholinergics
- Confusion
- Hallucinations
- Postural hypotension
- Urinary tract infections
Pramipexole
Non-ergot dopamine agonists at D2 receptors
First line therapy in younger patients
An adjunct to L-dopa / carbidopa treatment in patients with advanced Parkinson’s disease
- Dyskinesia
- Insomnia / somnolence (drowsiness)
- Dizziness
- Postural hypotension
Ropinirole
Non-ergot dopamine agonists at D2 receptors
First line therapy in younger patients
An adjunct to L-dopa / carbidopa treatment in patients with advanced Parkinson’s disease
- Dyskinesia
- Insomnia / somnolence (drowsiness)
- Dizziness
- Postural hypotension
Rotigotine
Non-ergot dopamine D2-like receptor agonist at clinical doses
Transdermal patches when used in the treatment of Parkinson’s disease *elderly
- Application site: hypersensitivity, skin problems e.g. redness, rashes, itching, irritation, burning sensation, etc
- Dizzy, Headache, Nausea
Selegiline
Selective monoamine oxidase B inhibitor
Decrease metabolism of dopamine in periphery and brain
Increase dopamine levels in brain (for patients with mild parkinsonism)
Enhance effects of L-dopa / carbidopa (as an adjuvant)
High dose: hypertensive crisis
- High level of dopamine in periphery
Rasagiline
Selective monoamine oxidase B inhibitor
Decrease metabolism of dopamine in periphery and brain
Increase dopamine levels in brain (for patients with mild parkinsonism)
Enhance effects of L-dopa / carbidopa (as an adjuvant)
High dose: hypertensive crisis
- High level of dopamine in periphery
Entacapone
Catechol-O-methyl transferase (COMT) inhibitors
Block peripheral conversion of levodopa to 3-O-methyldopa
(use the same active carrier as dopamine to cross BBB)
Used only as adjuncts to L-dopa / carbidopa therapy
- Diarrhoea
- Postural hypotension
- Dyskinesia
- Sleep disorders
- Hallucinations
Tolcapone
Catechol-O-methyl transferase (COMT) inhibitors
Block peripheral conversion of levodopa to 3-O-methyldopa
(use the same active carrier as dopamine to cross BBB)
Used only as adjuncts to L-dopa / carbidopa therapy
- Diarrhoea
- Postural hypotension
- Dyskinesia
- Sleep disorders
- Hallucinations
- Hepatic necrosis (for tolcapone only)
COMT inhibitors
Entacapone
Tolcapone
Selective MAO-B inhibitor
Selegiline
Rasagiline
Amantadine
Antiviral agent for influenza
Unknown mechanism
- Enhance release of dopamine from surviving nigral neurons
- Inhibit reuptake of dopamine at synapses
More effective than anticholinergic agents in improving bradykinesia and rigidity when used along with L-dopa / carbidopa
- Restlessness, agitation, confusion
- Postural hypotension
- Peripheral edema
- Skin rash
Anticholinergics for Parkinson’s
Benztropine
Benhexol
Biperidine
Reduce cholinergic output of the striatum (inhibition to basal ganglia)
Much less efficacious than levodopa / carbidopa
As adjuvant only:
- Reduce primary symptoms e.g. tremor, rigidity and akinesia (NOT bradykinesia)
- Reduce secondary symptom e.g. drooling
(Add to L-dopa and carbidopa for control of tremor)
Current best treatment for Parkinson’s
L-dopa + carbidopa / benserazide)
To control motor fluctuations in Parkinson’s
COMT inhibitor / MAO-B inhibitor
+
L-dopa/carbidopa
Huntington’s
- Medications for movement disorder:
Tetrabenazine: ‘dopamine-depleting’ to suppress chorea (involuntary jerking and writhing movement)
Anti-psychotic drugs: haloperidol, risperidone (newer) - Side effect of suppressing movement
- Medications for psychiatric disorders:
Anti-depressants: fluoxetine (SSRI)
Mood-stabilizing drugs: carbamazepine (treat irritability)
Movement disorder in Hungtinton’s
Tetrabenazine: ‘dopamine-depleting’ to suppress chorea (involuntary jerking and writhing movement)
Anti-psychotic drugs: haloperidol, risperidone (newer)
- Side effect of suppressing movement
Medications for psychiatric disorders in Huntington’s
Anti-depressants: fluoxetine (SSRI)
Mood-stabilizing drugs: carbamazepine (treat irritability)
Tetrabenazine
‘dopamine-depleting’ to suppress chorea in Huntington’s(involuntary jerking and writhing movement)
Haloperidol
Anti-psychotics
For movement disorders in Huntington’s
Risperidone
Anti-psychotics
For movement disorders in Huntington’s
Fluoxetine
SSRI
Also for psychiatric disorder in Huntington’s
Carbamazepine
Mood-stabilizing for Huntington’s
Drugs for Alzheimer’s
AChEI:
- Donepezil
- Rivastigmine (transdermal patch)
- Galantamine
Uncompetitive NMDA receptor antagonist
- Memantine
AChEI for Alzheimer’s
- Donepezil
- Rivastigmine (transdermal patch)
- Galantamine
Increase the amount of ACh available by preventing its breakdown within the synaptic cleft
improve cholinergic transmission within CNS
- Nausea, vomiting
- Diarrhoea, abdominal cramps
- Anorexia (appetite and weight loss)
- Agitation
- Dizziness
- Urine incontinence
Uncompetitive NMDA receptor antagonist for Alzheimer’s
Memantine
Protect CNS neurons from excitotoxic effects of glutamate
(excess Mg removal excess Ca influx kill neurons)
Improve cognitive ability
- Headache
- Dizziness
- Confusion
- Constipation
- Diarrhoea
Donepezil
AChEI
For Alzheimer’s (All stages)
Increase the amount of ACh available by preventing its breakdown within the synaptic cleft
improve cholinergic transmission within CNS
- Nausea, vomiting
- Diarrhoea, abdominal cramps
- Anorexia (appetite and weight loss)
- Agitation
- Dizziness
- Urine incontinence
Rivastigmine
AChEI
For Alzheimer’s (Transdermal)
Increase the amount of ACh available by preventing its breakdown within the synaptic cleft
improve cholinergic transmission within CNS
- Nausea, vomiting
- Diarrhoea, abdominal cramps
- Anorexia (appetite and weight loss)
- Agitation
- Dizziness
- Urine incontinence
Memantine
For Alzheimer’s (uncompetitive NMDA receptor antagonist)
Protect CNS neurons from excitotoxic effects of glutamate
(excess Mg removal excess Ca influx kill neurons)
Improve cognitive ability
- Headache
- Dizziness
- Confusion
- Constipation
- Diarrhoea