Neuro Flashcards
Levodopa
Indication: parkinsons (early stages)
Route: oral - absorbed by AT - in comp with amino acids (high protein meals)
- standard dosage
- controlled release preparations
- dispersible madopar - liquid so easier to swallow
Action:
- cross BBB
- taken up by dopaminergic cells in the substantia nigra
- converted to dopamine by dopa decarboxylase
- highly effacious (lost over time due to loss of neurones)
Adverse effects:
- nausea/vomiting
- hypotension
- psychosis
- tachycardia
- involuntary movements
- motor complications
Interactions: pyridoxine/vitamin B6 increases peripheral breakdown of levodopa
Other:
- 90% inactivated in intestinal wall due to monoamine oxidase and dopa decarboxylase
- 9% converted to dopamine in peripheral tissues
- used in combo with a peripheral dopa decarboyxlase inhibitor (reduces dose required, side effects, increase levodopa reaching brain)
- short half life (2hrs) - short dose interval and fluctulations in blood levels and symptoms
Sinemet, madopar
Levodopa in combination with peripheral dopa decarboxylase inhibitor
Sinemet = levodopa + carbidopa Madopar = levodopa + benserazide
Entacapone, opicapone, stalevo
Indication: parkinsons
Class: Catechol-o-methyl transferase (COMT) inhibitors
Action: reduce peripheral breakdown of levodopa to 3-O-methyldopa - levodopa sparing effect
Other:
- no therapeutic effect alone - always with levodopa (and dopa decarboxylase inhbitor)
Stalevo = levodopa, peripheral dopa decarboxylase inhibitor, COMT inhibitor
Ropinirole, pramipexole, rotigotine, apomorphine
Indication: parkinsons
- de novo therapy
- add on therapy
- apomorphine for severe motor fluctuations
Class: dopamine receptor agonists - less efficacy than levodopa
Route:
- Oral = ropinirole, pramipexole
- patch = rotigotine
- subcutaneous = apomorphine
Adverse effects:
- impulse control disorders e.g pathological gambling, punding
- more pyschiatric side effects e.g hallucinations
- sedation
- confusion
- nausea
- hypotension
Other:
- less dyskinesias/motor problems than levodopa
- possible neuroprotection
Rasagaline, safinamide
Indication: parkinsons
- used alone
- used alongside levodopa to prolong action
Class: monoamine oxidase B inhibitors
Action: prevent metabolism of dopamine
Adverse effects: at high dose can risk hypertensive crisis
Trihexyphenidydyl, orphenarine, procylidine
Indication: parkinsons
- treat tremors
Class: anticholinergics - not acting via dopamine system so does not rely on neuron number
Disadvantages:
- no effecr on bradykinesia
- confusion and drowsiness
Amantadine
Indication: parkinsons
- levodopa induced dyskinaesia
Can cause hallucinations and confusion
Pyridostigmine
Indication: myasthenia gravis
Class: acetycholineesterase inhibitor
Route: oral
- onset = 30 mins
- peak = 60-120 mins
- Duration = 3-6 hrs
- dose interval and timing crucial
Action:
- prevent breakdown of Ach
- higher conc remains in the synaptic cleft
- enahnce neuromuscular transmission
Adverse effects:
- SSLUDGE syndrome (muscarinic side effect)
- excess dose = cholinergic crisis
Other: manage the autoimmune side of myasthenia gravis via normal routes e.g corticosteroids, azathioprine
