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Clinical Pharmacology, Therapeutics & Principles of Prescribing > Anti-Epileptic Drugs > Flashcards

Anti-Epileptic Drugs Flashcards

1
Q

Epilepsy can be classified into which two main types?

A

Partial seizures

Generalised seizures

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2
Q

What is another name for partial seizures?

A

Focal seizures

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3
Q

Partial seizures can be sub-divided into what categories?

What is the difference between the two?

A

Simple (conscious)

Complex (impaired consciousness)

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4
Q

During a focal seizure, symptoms reflect what?

A

The area affected by the seizure

Including involuntary motor disturbance, behavious change

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5
Q

Generalised seizures can be subdivided into which types?

How do these types differ

A

Tonic-clonic seizure: rigidity followed by muscle contraction

Absence seizure: no shaking, unable to respond to stimuli

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6
Q

What is status epilepticus?

A

A prolonged seizure beyond 5 minutes or as a series of seizures without any recovery interval

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7
Q

List some of the dangers associated with severe epilepsy

A

Injury relating to fall/crash

Hypoxia

Sudden death in epilepsy

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8
Q

What is the difference between primary and secondary epilepsy?

A

Primary: no identifiable cause (idiopathic)

Secondary: caused by another medical condiiton e.g. vascular disease, tumour

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9
Q

List some precipitating factors of epilepsy

A

Sensory stimuli: flashing lights

Brain disease/Trauma: head injury, stroke, drugs, lesion

Metabolic disturbance: Hypo-glycaemia,calcaemia,natraemia

Infections: febrile convulsions in infants

Therapeutics: AEDs + polypharma

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10
Q

What are the two established therapeutic targets for anti-epileptic drugs?

A

Voltage-gated sodium channel blockers

Enhanced GABA-mediated inhibition

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11
Q

Where do volatage gated sodium channel blockers bind to elicit their effect?

A

The inside of the membrane, on domain 1V

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12
Q

Briefly explain the mechanism of VGSC blockers in the treatment of epilepsy

A

VGSc blockers access the binding site during depolarisation- making it voltage dependent

This prolongs the inactivated state

Firing rate returns to normal

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13
Q

VGSCs have three states, what are they?

At which stage to VGSC blockers act?

A
  1. Open (resting)
  2. Closed (activated)
  3. Inactivated (closed to Na+ via inactivation gate)
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14
Q

What does Carbamezepine work?

A

It prolongs VGSC inactivation state to allow the firing rate to go back to normal

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15
Q

List some adverse drug reactions of carbemazepine

A

CNS effects: dizziness, drowsiness, ataxia, numbness, tingling

GI effects: vomiting

CVS: variation in BP

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16
Q

What feature of carbamezepine means that it can effect other drugs?

A

It is a strong inducer of CYP450

17
Q

Which seiure types may be treated with carbamezepine?

A

All partial

Generalised: Tonic-clonic

Not: absence

18
Q

At therapeutic levels, what pharmacokinetics does Phenytoin display?

What does this mean for its use clinically?

A

Non-linear

Has a very variable half life (6-24 hours)

Means that therapeutic dose is very variable

19
Q

List some ADRs of Pheytoin

A

CNS: dizziness, headache, nervousness

Gingival hyperplasia (20%)

Rashes, hypersensitivity

20
Q

What kind of monitoring is involved in the use of Phenytoin?

A

Monitoring of free concentration in plasma

21
Q

Which type of seizure can be treated with Pheytoin?

A

Generalised tonic-clonic

All: partial seizures

NOT: absence seizures

22
Q

Why is Lamotrigine increasingly being used as a first line drug, over Pheytoin and Carbamezepine, for the treatment of epilepsy?

A

It is well absorbed

It displays linear pharmacokinetics

Fewer ADRs and DDIs

May be safer in pregnancy

23
Q

Which seizures can Lamotrigine be used to treat?

A

Partial seizures

Generalised: tonic-clonic AND absence seizures

+other subtypes

24
Q

What is the general mechanism of GABA mediated inhibition of excitatory neurones?

A

GABA (or GABA agonist) binding increases the Cl- current into the neurone

This increases the threshold for AP generation

Making it harder for AP to be generated

25
Q

What is Valporate’s mechanism of action?

A

1) It is a weak inhibitor of GABA inactivation enzymes and a weak activatory of GABA synthesising enymes which both lead to increased GABA
2) It is a VGSC blocker and a weak Ca2+ blocker- both of which decrease discharge firing

26
Q

What kind of pharmacokinetics does Valporate display?

What is its half life?

A

Linear kinetics

Half life: 15 hours

27
Q

What drug monitoring is required in patients that are treated with Valporate?

A

Monitor free plasma concentration- though this does not correlate well with efficacy

Blood, hepatic and metabolic function should be monitored

28
Q

What types of epilepsy can be treated with Valporate?

A

Partial seizures

Generalised: tonic-clonic AND absence seizures

29
Q

What is the mechanism of action of Benzodiazepines?

A

They are positive allosteric effectors of GABA receptors

Act on GABA receptor to increase Cl- current into neurone

Increases the threshold for AP generation

Harder to generate AP

30
Q

List some adverse drug reactions of Benzodiazepines

A

Sedation

Tolerance with chronic use

Respiratory/CNS depression

31
Q

Which epilepsy types can be treated using Benzodiazepines?

A

Status epilepeticus- only SHORT-term

Absence seizure- only SHORT-term

32
Q

What are some importants things to consider when using anti-epileptic drugs during pregnancy?

A

To consider each patient individually

Take stage of pregnancy into account

Balance the risk of treatment with the risk of harm due to seizure

33
Q

Valporate poses the risk of what if used during pregnancy?

A

Neural tube defects

34
Q

The use of multiple AEDs during pregnancy is associated with an increased risk of what?

A

Tetatogenicity

35
Q

Which dietary supplementation can be taken by women taking AEDs to reduce the risk of neural tube defects in the baby?

A

Folate

36
Q

Which dietary supplementation can be taken by women taking AEDs to reduce the risk of coagulopathy and cerebral haemorrhage in the baby?

A

Vitamin K

37
Q

What are the main priorities when dealing with a patient with status epilepticus?

A

ABCDE

Exclusion of hypoglycaemia

High AED doses may result in hypoventilation

ITU may be required: paralysis and ventilation

38
Q
A

Clinical Pharmacology, Therapeutics & Principles of Prescribing (22 decks)

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