Pharmacology of Epilepsy Flashcards

1
Q

What are the 4 most common main drug classes prescribed for epilepsy / convulsions?

A
  1. Lamotrigine
  2. Sodium valproate
  3. Diazepam
  4. Levetiracetam
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2
Q

What is the primary mechanism of action for Lamotrigine?

A

Blocks voltage gated Na+ channels preventing Na+ influx

Prevents depolarisation of glutamatergic neurones and reduces glutamate excitotoxicity

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3
Q

What is the drug target site for Lamotrigine?

A

Voltage gated Na+ channels

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4
Q

What are the main side effects for Lamotrigine?

A

Side effects:

Common: Rash, drowsiness

Less common but serious:

Steven-Johnson’s syndrome, suicidal thoughts

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5
Q

What condition is Lamotrigine particularly useful for?

A

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

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6
Q

What is the primary mechanism of action for Sodium valproate?

A

Inhibition of GABA transaminase prevents the breakdown of GABA
This increases GABA concentrations directly in the synapse presynaptically and also indirectly prolongs GABA in the synapse due to the fact that extraneuronal metanolism of GABA is slowed which also slows GABA removal from the synapse

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7
Q

What is the drug target site for Sodium valproate?

A

GABA transaminase

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8
Q

What are the main side effects for Sodium valproate?

A

Side effects (MANY):

Common: Stomach pain and diarrhoea, drowsiness, weight gain, hair loss

Serious:

hepatotoxicity, teratogenicity, pancreatitis

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9
Q

How can Sodium valproate impact other drugs?

A

Broad CYP enzyme inhibitor - increases serum concentration of many co-administered drugs



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10
Q

What is the primary mechanism of action for Diazepam?

A

Increases choride ion influx in response to GABA binding at the GABA A receptor. Increased chloride ion influx associated with hyperpolarisation of excitatory neurones

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11
Q

What is the drug target site for Diazepam?

A

Benzodiazepine site on the GABA A receptor

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12
Q

What are the main side effects for Diazepam?

A

Side effects:

Common: Drowsiness, respiratory depression (if i.v. or at high dose)

Uncommon but serious:

Haemolytic anaemia, jaundice

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13
Q

Why is Diazepam not given long term?

A

Main reason that diazepam is not used for long term suppression of seizures is due to the development of tolerance

Diazepam is a Schedule 4 controlled drug - addiction prone individuals more likely to become dependent on diazepam

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14
Q

What is the primary mechanism of action for Levetiracetam?

A

Inhibition of the synaptic vesicle protein SV2A. It inhibits this protein and prevents vesicle exocytosis. A reduction in glutamate secretion is reduces glutamate excitotoxicity

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15
Q

What is the drug target site for Levetiracetam?

A

Synaptic vesicle protein SV2A

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16
Q

What are the main side effects for Levetiracetam?

A

Common:

dizziness, somnolence, fatigue and headache

17
Q

What makes Levetiracetam a favourable drug?

A

The metabolism of levetiracetam has no effect on the cytochrome P450 enzyme system so it is favorable in terms of no drug–drug interactions

18
Q

What are the first three steps for pharmacology?

A

Identify the patient’s problem
Specify the therapeutic objective
Select a drug

19
Q

What are the types of seizures?

A
Absence
Focal
Generalised tonic-clonic
Myoclonic
Tonic or atonic
20
Q

What are the stages of tonic-clonic seizures?

A

Tonic stage: lose of consciousness, stiffening of the body

Clonic stage: Jerking or shaking of pats of the body

21
Q

What does an EEG show for epilepsy?

A

Interictal epileptiform discharge - risk of seizure recurrence

22
Q

What is the therapeutic objective for the patient?

A

Reduce severity of seizures
Reduce frequency of seizures
Prevent long term effects
Identify triggers (stress, lack of sleep etc.)
Educate patient
Friends and family should be educated on management of seizures

23
Q

What are the main goals of anti-epileptic drug treatment?

A

Eliminate seizures or reduce frequency
Evade the adverse effects associated with long term treatment

Aid patients in maintaining or restoring their usual psychical and vocational activities and in maintaining a normal lifestyle

24
Q

What drugs could be give to treat tonic-clonic seizures in women of child bearing age?

A

Lamotrigine or Carbemazepine

25
Q

What is the mechanism of action of Lamotrigine?

A

Blocks voltage gated Na+ channels preventing Na+ influx

Prevents depolarisation of glutamatergic neurones and reduces glutamate excitotoxicity

26
Q

Why is sodium valproate not given to women of child bearing age?

A

Can cross placental barrier and cause physical birth defects or developmental uses

e.g. Neural tube defects
Decreased IQ

27
Q

Why might the OCP affect Lamotrigine concentration?

A

OCP may impact lamotrigine absorption so less gets into the blooding the first place

OCP may enhance metabolism so more is cleared from the blood

OCP may enhance excretion of Lamotrigine

28
Q

A patient on lamotrigine begins taking the OCP, why might she be feeling more drowsy during the fourth week of her cycle?

A

During the fourth week of contraceptive cycle you stop taking the OCP

Therefore the concentration of the anti-epileptic while be twice as high in the fourth week as there is nothing reducing its concentration.

Increasing the side effects of Lamotrigine one of which is drowsiness

29
Q

What are the side effects of Lamotrigine?

A
Dizziness
Diarrhoea
Loss of balance
Abnormal eye movements
Trouble speaking
Drowsiness
30
Q

What is the mechanism of action levetiracetam?

A

Inhibition of the synaptic vesicle protein SV2A

It inhibits this protein and prevents vesicle exocytosis

A reduction in glutamate secretion is reduces glutamate excitotoxicity

31
Q

What is the mechanism of action of Sodium Valproate?

A

Inhibition of GABA transaminase prevents the breakdown of GABA

This increases GABA concentrations directly in the synapse presynaptically and also indirectly prolongs GABA in the synapse due to the fact that extraneuronal metanolism of GABA is slowed which also slows GABA removal from the synapse

32
Q

What adjuvant therapy would you offer the patient?

How would administration differ in community or in hospital?

A

Benzodiazepines e.g. IV lorazepam

But continue usual therapy

In community take drug orally due to absence of trained staff to administer IV or rectally

33
Q

What is the impact of female gonadal hormones of seizure frequency?

A

Oestrogens are generally thought of as seizure promoting and progesterone has been shown to be seizure inhibiting. Many women have an increased frequency of seizures during a particular phase of the ovulatory cycle e.g. day 10-13 (periovulatory estrogen peak)

34
Q

What is myoclonic?

A

brief, jerking spasms of a muscle or muscle group