Neuro Flashcards
what is the classname of phenytoin
phenytoin
indication for phenytoin
to control seizure in status epilepticus where benzodiazepines are ineffective
to reduce the frequency of generalised or focal seizures in epilepsy
a few side effect and interaction
MOA for phenytoin
incompletely understood
reduces neuronal excitability and electrical conductance among brain cells which inhibits the spread of seizure activity
binding to neuronal Na+ channels in their inactive state, prolonging inactivity and preventing Na+ influx into neurons and stopping membrane potential
this effect also happen in the heart and so have antiarrythmic and cardiotoxic effect
side effect of phenytoin
long term use - change in appearance
- skin coarsening acne, hirsutism and gum hypertrophy
cerebellar toxicity, impaired cognition and consciousness is related to dose
haematological disorder and osteomalacia by inducing folic acid and vit D metabolism
death through cardiovascular collapse and resp depression
contra-indication of phenytoin
metabolised by the liver with zero-order kinetics (at constant rate regardless of serum conc)
low therapeutic index = small doses
should be reduced in in hepatic impairment
fetal hydantoin syndrome if exposed during pregnancty
pregnant lady should take high dose folic acid before conception
where is phenytoin metabolised
liver
interaction of phenytoin?
it is an enzyme induce so reduces plasma conc of efficacy of drug metabolised by p450 eg warfarin etc
adverse effect increase when used with cytochrome P450 inhibitors
other antiepileptic drugs - complex interactions
efficacy of anti epileptic drugs are reduced by drugs that lower the seizure threshold eg SSRI, tricyclic anti-depressants etc
what class of drug is Levodopa
Dopaminergic drugs for parkinson’s disease
main indication for Levodopa
early Parkinson’s disease when dopamine agonist (ropinirole, pramipexol) maybe preferred over levodopa
later parkinson’s disease, levodopa is an integral part of management while dopamine agonist agonists are an option for add-on therapy
levodopa and dopamine agonist maybe an option for secondary parkinsonism
MOA for dopaminergic agonist
levodopa is a precursor of dopamine which can enter the BBB.
Ropinirole and pramipexol are relatively selective agonist for D2 receptor whihc predominates in the striatum
increase dopaminergic stimulation to the striatum
side effect of dopaminergic agonist
nausea, drowsiness, confusion, hallucinations and hypotension
levodopa - wearing off effect - where symdroms worsen towards the end of the dosage interval and worsen as the duration of the therapy increase
on-off effect - when opposite effect of dopaminergic agonist - excessive and involuntary movments at the beginning of the dosage interval
contra-indiction for dopaminergic agonist
should be used with caution in elderly and those with existing cognitive/psychiatric disease due to risk of confusion and hallucinations
should be used catiously in those with cardiovascular disease due to risk of hypotension
interaction of dopaminergic agonist
levodopa is always given with a peripheral dopa-decarboxylase inhibitor to reduce its conversion to dopamine outside the brain which reduces nausea and lowers dose needed for theraputic effect
should not be used with antipsycotics or metoclopramide as effect on dopamine receptors are contradictory
what are the different cominbation of levodopa
only available with peripheral dopa-decarboxylase inhibitors - with benserazide (co-beneldopa) or carbidopa (co-careldopa)
what are some example of anticonvulsants
carbamazepine, phenytoin, sodium valproate, lamotrigine, levitaracetam
