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SA Clinical Pharmacology & Therapeutics > S12) Anti-epileptic Drugs > Flashcards

S12) Anti-epileptic Drugs Flashcards

1
Q

What is a seizure?

A

A seizure is an event of sudden excessive depolarisation/electrical activity in the neurones → sudden and temporary

(not everyone who has seizures has epilepsy)

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2
Q

what other conditions can present with similar features to epilepsy

A

→ vasovagal syncope

→ cardiac arrhythmia

→ panic attacks or hyper ventilation

→ TIA

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3
Q

What is epilepsy?

A

Epilepsy is a condition wherein a patient experiences more than one episode of unprovoked seizures

→ prevalence increases with age

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4
Q

what are some differential diagnosis of children with epilepsy

A

→ febrile convulsions

→ breath holding attacks

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5
Q

Distinguish between primary and secondary epilepsy

A
  • Primary – idiopathic (no identifiable cause)
  • Secondary – identifiable cause e.g. head injury, hypoxia, tumour, stroke, infection, hypoglycaemia, drugs
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6
Q

what are some risk factors of epilepsy

A

→ premature birth

→ genetic conditions

→ cerebrovascular disease

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7
Q

How does one classify seizures?

A
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8
Q

Describe some of the major recognised precipitants of epilepsy

A
  • Sensory stimuli e.g. flashing lights/strobes
  • Brain disease / trauma e.g. brain injury, stroke, haemmorrhage
  • Drugs/ Alcohol
  • Metabolic disturbances e.g. hypoglycaemia/calcaemia/natraemia
  • Infections e.g. febrile convulsions in infants
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9
Q

how do you make a diagnosis

A

→ urget referral after first seizure

→ asses risk of second seizure

→ info on how to recognise seizure

MRI, ECG

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10
Q

What are the prescribing aims for a patient with epilepsy?

A
  • Aim is for monotherapy – if one drug isn’t working despite increasing the dose, another should be tried
  • Aim to start at a low dose and increase slowly – attempt to achieve seizure control at lowest possible dose to avoid side effects
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11
Q

Why must anti-epileptic drugs be monitored during pregnancy?

A
  • All anti-epileptic drugs are teratogenic
  • One must weigh up risk to mum & baby of having a seizure during pregnancy due to poor control and birth defects
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12
Q

What are the congenital abnormalities of using anti-epileptic drugs during preganancy?

A
  • Neural tube defects
  • Valproate syndrome
  • Learning difficulties
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13
Q

Illustrate the effects of sodium valproate syndrome on an infant

A
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14
Q

What is the indication for benzodiazepines?

A

Benzodiazepines is a first line therapy for acute life threatening status epilepticus or any acute seizure that has not terminated in 5 mins

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15
Q

Provide some examples of benzodiazepines and when they are used respectively

A
  • Lorazepam – IV bolus 4mg is first line in emergency
  • Midazolam – buccal if no IV access in emergency
  • Diazepam – can be given rectally if no access
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16
Q

In four steps, describe the mechanism of action of benzodiazepines

A

⇒ Enhancement of GABA action (inhibitory receptor in brain)

⇒ Results in increased Chloride current into neurone

⇒ Increases threshold for action potential generation

⇒ Decreases chance of reaching seizure threshold

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17
Q

Provide four examples of sodium channel blockers

A
  • Sodium Valproate
  • Lamotrigine
  • Phenytoin
  • Carbamazepine
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18
Q

In four steps, describe the mechanism of action of sodium channel blockers

A

⇒ Inhibition of voltage gated Na+ channel function by binding during depolarisation

⇒ Prolongs inactivation state (cannot stimulate another AP)

⇒ Reduces probability of high abnormal spiking activity (firing lots of action potentials)

⇒ VGSC blocker detaches once neurone membrane potential normalises

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19
Q

What is the indication for Sodium Valproate?

A

Sodium Valproate as first line therapy for primary generalised tonic–clonic seizures

20
Q

Describe the possible drug interactions of Sodium Valproate

A
  • Antidepressants – SSRIs, MAOIs, TCAs inhibit action of Valproate
  • Antipsychotics – antagonise Valproate by lowering convulsive threshold
  • Aspirin – competitive binding in plasma Valproate
21
Q

Identify some adverse drug reactions of Sodium Valproate

A
  • Most teratogenic (sodium valproate syndrome)
  • thrombocytopenia
  • Weight gain
  • Hepatic function (40% elevated transaminases)
  • Hepatic failure (rarely)
22
Q

what is the mechanism of action of Carbamazepine

A

→ use-dependant blockage of Na channels and reduced Ca influx and reduced glutamate

23
Q

What is the indication for carbamazepine?

A

Carbamazepine as first line therapy for generalised tonic–clonic and all partial seizures

24
Q

Describe the possible drug interactions of carbamazepine

A
  • Decreases effect of many drugs – warfarin, OCP, steroids, phenytoin (strong CYP450 enzyme inducer)
  • Contraindicated use with antidepressants
25
Q

What are the adverse drug reactions of carbamazepine?

A
  • General: dizziness, drowsy, ataxia, motor disturbance, numbness, tingling
  • Rare: neutropenia
26
Q

Iamotrigine moa

A

Na and Ca channel blocker

→ can cause aggression and agitation

→ phase 2 metabolism has a long half life

→ cont react with sodium valproate, phenytoin

27
Q

What is the indication for lamotrigine?

A

Lamotrigine can be used in either general/partial circumstances, and is probably the drug of choice for women of childbearing age (least teratogenic)

28
Q

What is the indication for phenytoin?

A
  • Phenytoin is a first line therapy for acute life threatening status epilepticus or any acute seizure (generalised tonic-clonic, all partial) that has not terminated after 10 mins
  • It is used in emergency as a loading dose + infusion

→ it is 0 order and dependant on the blockage of Na channels

→ hard to manage

29
Q

Describe the possible drug interactions of phenytoin

A

Decreases the effect of many drugs – warfarin, OCP, steroids (CYP450 enzyme inducer)

30
Q

What are the adverse drug reactions of phenytoin?

A
  • Gingival hyperplasia (20%)
  • Rashes – hypersensitivity → Stevens Johnson (2-5%)
31
Q

why is it relevant to know that phenytoin is zero order

A

→ zero order kinetics means rate of elimination is constant despite adding more drug = drug becomes toxic

→ it has a unpredictable half life so hard to predict drugs conc over time

32
Q

In four steps, outline the process for emergency seizure management

A

⇒ ABCDE approach

⇒ 4mg Lorazepam IV / 5mg diazepam PR

⇒If not terminating after 5 minutes, give further dose

⇒ If not terminating after 5-10 minutes, give IV phenytoin loading dose + infusion (call for help)

33
Q

what are some examples of focal seizures

A
34
Q

what are some examples of generalised seizures

A
35
Q

classification of seizures

A
36
Q

Prodrome

A

early signs or symptoms a seizure may be coming hours to days before

37
Q

Aura

A

a “warning” – focal aware seizure leading to secondary generalised

38
Q

Ictal

Interictal

A
  • Ictal – during a seizure
  • Interictal – between seizures often in reference to EEG
39
Q

Post ictal

A

begins as seizure subsides – last minutes (to hours)
e.g. confusion, lack of consciousness, fatigue, headache, anxiety, frustration, embarrassment, muscle aching or pain, injury!

40
Q

ldvdtiracetam

A
41
Q

initiating and titrating doses

A

→ start at a low dose and gradually increase, aim is to be seizure free balanced with an acceptable amount of side effects

→ drug cons should be changed slowly by titration

42
Q

what are some adverse effects of benzodiazepines

A

ataxia, depression, drowsiness, hypotension

43
Q

what are some adverse effects of benzodiazepines

A

ataxia, depression, drowsiness, hypotension

44
Q

order of treatment for epilepsy

A
45
Q

What do AEDs split into

A

SA Clinical Pharmacology & Therapeutics (36 decks)

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