(pharm) pharmacology of anticonvulsants Flashcards by Rasha Rashid

what are the most common drugs prescribed for epilepsy?

lamotrigine
sodium valproate
diazepam
levetiracetam

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explain the primary mechanism of action of lamotrigine

blocks voltage-gated Na+ channels preventing Na+ influx = prevents depolarisation of glutamatergic neurones and reduces glutamate excitotoxicity

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what is the drug target for lamotrigine?

voltage-gated Na+ channels

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what are the most common side effects of lamotrigine?

rash, drowsiness

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what are the less common side effects of lamotrigine?

Steven-Johnson’s syndrome, suicidal thoughts

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how is lamotrigine used to prevent allergic skin reactions?

introducing lamotrigine gradually is one of the keys to reducing the frequency and severity of allergic skin reactions

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explain the primary mechanism of action of sodium valproate

inhibition of GABA transaminase prevents the breakdown of GABA = increases GABA concentrations directly presynaptically + indirectly prolongs GABA in the synapse due to the fact that extraneuronal metabolism of GABA is slowed (which also slows GABA removal from the synapse) = overstimulation of inhibitory neurones due to prolonged presence of GABA in the synapse

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what is the drug target for sodium valproate?

GABA transaminase

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what are the common side effects of sodium valproate?

stomach pain

diarrhoea

drowsiness

weight gain

hair loss

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what are the less common side effects of sodium valproate?

hepatotoxicity

teratogenicity

pancreatitis

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what is the broad classification of sodium valproate?

braod CYP enzyme inhibitor

increases the serum concentration of many co-administered drugs

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what is the drug target for diazepam?

benzodiazepine site on the GABA A receptor

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what are the most common side effects of diazepam?

drowsiness, respiratory depression (if IV or at high dose)

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what are the less common side effects of diazepam?

haemolytic anaemia, jaundice

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when can respiratory depression occur when diazepam is administered?

if diazepam is given at high doses or if IV diazepam is administered

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what is the main reason that diazepam is not used for the long-term suppression of seizures?

due to the development of tolerance

diazepam is a schedule 4 controlled drug - what does this mean?

addicition-prone

individuals are more likely to become dependent on diazepam

diazepam is a schedule 4 controlled drug - what does this mean?

addiction-prone

individuals are more likely to become dependent on diazepam

explain the mechanism of action of levetiracetam

inhibition of the synaptic vesicle protein SV2A = prevents vesicle exocytosis

so less glutamate secretion reduces glutamate excitotoxicity

what is the drug target for levetiracetam?

synaptice vesicle protein SV2A

what are the common side effects of levetiracetam?

dizziness

somnolence (i.e. drowsiness)

fatigue

headaches

why is levetiracetam favourable?

has no effect on the cytochrome P450 enzyme system = favourable in terms of no drug-drug interactions

how do you rule out that a seizure is not just a one-off episode?

do an EEG (electroencephalogram)

what will appear on an EEG if there is increased brain activity in between seizures?

IEDs = interictal epilepriform discharge

what are IEDs?

interictal epilepriform discharge = sharp waves that are characteristic of epilepsy appear as hyperactivity in specific areas

what does the presence of IEDs on an EEG suggest?

increase risk of seizures within next two years (increased risk of recurrence) = pharmacological treatment advised

what must you ensure to do when a patient presents to A&E with recurrent seizures?

must inform DVLA that they cannot drive MUST MAKE A NOTE IN MEDICAL NOTES

what is the therapeutic objective for patients that present with recurrent seizures?

reduce risk of recurrence of seizures (drugs to reduce the risk of seizures in the future) reduce severity of the seizure in the moment (drugs to stop seizure in the moment) tackle the triggers (stress from university and lack of sleep) avoid adverse effects associated w long-term treatment (fertility etc) maintain a normal lifestyles

why can sodium valproate not be given to women with potential fertility?

as it is teratogenic (can cause neural tube defects and decreased IQ in foetuses)

which drug is administered to patients when they have a seizure in hospital?

IV diazepam or IV lorazepam

why is diazepam/lorazepam administered intravenously during a seizure?

patients cannot swallow and drug needs to act fast (administer as close to site of action as possible)

how does lamotrigine interact with the combine oral contraceptive pill?

taking both lamotrigine and the COC will reduce lamotrigine concentrations in the blood (reduced efficacy) however the plasma COC levels are unaffected

how is the problem of lamotrigine and combine oral contraceptive pill interaction overcome?

taking both lamotrigine and the COC will reduce lamotrigine concentrations in the blood (reduced efficacy) SO increase the dose of lamotrigine (can also offer alternative contraceptive)

why are benzodiazepines given to address seizures in hospital but not in the community?

as repeated/prolonged intake of benzodiazepines = increased risk of dependency and tolerance so can have withdrawal symptoms

how do oestrogens and progesterones affect seizures?

oestrogens = seizure promoting progesterones = seizure inhibiting

how and why can seizures be affected by pregnancy?

(lamotrigine) dose may be reduced due to fears of harming the unborn child pregnancy may lead to changes in liver metabolism = (lamotrigine) levels may decrease and be associated with increased seizures

how can the anticonvulsant dose be determined for patients during pregnancy?

monitor patient and their response to drug dose during the beginning of the pregnancy dose can be adjusted to suit the second and third trimester

briefly explain the mechanism of action of benzodiazepines

target = benzodiazepine site on the GABA A receptor location = GABA A receptor effect = positive allosteric modulator so stimulates an even greater chloride ion influx into the cell, accentuating the hyperpolarisation