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Neuro > Neuro Drugs > Flashcards

Neuro Drugs Flashcards

1
Q

Drugs used to treat epilepsie (Anti-epileptic drugs/ AED)

A
  1. Reduce pre-synaptic excitability
    a. Voltage-gated Na+ channel antagonist (carbamazepine, lamotrigrine)
    b. Voltage-gated K+ channel agonist (retigabine)
  2. Stops neurotransmitter release
    a. SV2A vesicle antagonist (levetiracetam)
    b. Voltage-gated Ca2+ channel antagonist (pregablin and gabapentin)
  3. GABA-ergic system agonists
    a. GABA metabolism inhibitor (valproate, vigabatrin)
    b. GABA transporter antagonist (tiagabine)
  4. Reduces post-synaptic excitability
    a. GABA receptor agonist (benzodiazepines)
    b. AMPA and NMDA receptor antagonist
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2
Q

Carbamazepine Mechansm of action

A
  • voltage gated Na+ channel blocker on pre-synaptic membrane
  • Na+ influx increases excitability and drives action potentials
  • Drug bloks the Na+ influx, reduces neuronal excitability and decreased the action potential
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3
Q

Carbamazepine

A

Pre-synantic Na+ channel blocker

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4
Q

Carbamazepine indications

A

epilepsy, trigeminal neuralgia, neuropathic pain

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5
Q

Side effects of carbamazepine

A 
Dizziness
Dry mouth
Ataxia
Fatigue
Headache
Diplopia
Blurred vision
Hyponatraemia
Stevens-Johnson’s syndrome (rarely
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6
Q

Important PK/PD of carbamazepine

A

Response to the drug can be variable
Enzyme inducer of cytochrome P450; induces metabolism of itself
Interactions with other anti-convulsants
The transporter that can confer drug resistance is RALBP1
Grapefruit can significantly increase serum levels of this drug
HLA-B*1502 allele raises the risk for SJS; avoid in these patients

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7
Q

Patient information of carbamazepine

A

Avoid alcohol

Avoid grapefruit juice

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8
Q

Retigabine

A

Pre-synaptic K+ channel agonist

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9
Q

Mechanism of action of retigabine

A
  • voltage gated K+ channel agonist on pre-synaptic membrane
  • K+ efflux reduces neuronal excitability
  • Drug increases the channel activity reducing the action potential
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10
Q

Phenytoin

A

Pre-synaptic sodium channel blocker

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11
Q

Phenytoin mechanism of action

A
  • Acts as a voltage-gated Na+ channel blocker on the pre-synaptic neuronal membrane
  • Limits action potential transmission
  • Hence limiting spread of seizure activity
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12
Q

Indications for phenytoin

A

epilepsy (including status epilepticus

trigeminal neuralgia

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13
Q

Side effects of phenytoin

A 
MORE THAN CARBAMAZEPINE 
Insomnia
Headache
Rash
Constipation
Vomiting
Gingival hyperplasia
Liver damage

Stevens-Johnson Syndrome (rare)
Leucopenia (rare)
Thrombocytopenia (rare)

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14
Q

Important PK/PD of phenytoin

A

Enzyme inducer of cytochrome P450
Can cause interactions with other anti-epileptic drugs
Narrow therapeutic index
Relationship between dose and plasma concentration is non-linear

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15
Q

Patient information for phenytoin

A

Avoid alcohol
Do not take calcium, aluminum, magnesium or iron supplements within 2 hours of ingestion
Take with food to reduce irritation

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16
Q

Levetiracetam

A

Reduces neurotransmitter release by blocking SVA2

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17
Q

Levetiracetam mechanism of action

A
  • SV2A is a synaptic vesicle protein required for neurotransmitter release
  • Levetiracetam blocks this and reduced neurotransmitter release
  • Induces an anti-epileptic effect
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18
Q

Levetiracetam indication

A

epilepsy

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19
Q

Side effects of levetiracetam

A 
Headache
Fatigue
Anxiety
Irritability
Drowsiness
Constipation
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20
Q

Important PK/PD of levetiracetam

A
  • Rapidly and almost completely absorbed after oral administration (99%)
  • Food does not affect bioavailability
  • Cytochrome P450 is not involved in its metabolism
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21
Q

Patient information of levetiracetam

A
  • It might affect your ability to drive or operate machinery

- Not recommended during pregnancy and breastfeeding

22
Q

Pregablin and gabapentin

A

Blocks voltage gated Ca2+ channels to decrease neurotransmitter release

23
Q

Mechanism of action of pre-gablin

A
  • ca2+ influx drivers neurotransmitter release

- Channel inhibited by pregablin and gabapentin

24
Q

Tiagabine

A

Gabaergic system - GABA transporter

25
Q

Tiagabine mechanism of action

A
  • removes GABA from the synapse

- inhibited by tiagabine (to elevate GABA levels)

26
Q

Valproate

A

GABAergic system - GABA metabolism

27
Q

Valproate mechanism of action -

A
  • degrades GABA transaminases

- inhibited by valproate (to elevate GABA levels)

28
Q

Perampanel, felbamate and topiramte mechanism of action

A

Reduce post-synaptic effects

  • glutamate receptors are not selectively targeted by an approed AEDs
  • permapanel has main aactivity blocking AMPA receptors
  • Felbamate has weak affinity for NMDA receptors
  • Topirmate binds both AMPA and kainate receptors
29
Q

Benzodiazepines mechanism of action

A

Reduces neuronal excitability

  • GABAa receptor activity increased
  • Increase the frequency of channel openin which leads to increase in chloride ion conduction and inhibitor of the action potential
30
Q

Drugs for localised onset

A

lamotrigine, carbamazepine

31
Q

Drugs for generalised onset

A

Valproate, levetiracetam, lamotrigine

32
Q

Drugs used to treat parkinsons

A

Drugs that increase dopaminergic activity
a. dopamine precursors
b. dopamine agonists
c. drugs that stimulate dopamine release
d. MAO-B inhibitors
Drugs that inhibit strialtal cholinergic activity
a. anticholingeric agents

33
Q

Example of dopamine precursor

A
  • Levodopa
34
Q

Mechanism of action of L-dopa

A
  • Immedaite precursor of dopamine
  • Able to cross the blood-brain barrier to replenish dopamine content of the corpus striatum
  • L-dopa is decarboxylated to dopamine to dopamine in the brain by Dopa decarboxylase
  • beneficial effects on the actions of D2 receptors
35
Q

Indication of levodopa

A

parkinsons disease

36
Q

Side effects of levodopa

A 
dyskinesia 
compulsive disorders 
hallucinations 
nausea 
GI upset
37
Q

Important pharmacokinetics/ pharmacodynamics for l-dopa

A
  • Converted to dopamine in peripheries (which can cause the motor side effects)
  • Given with a dopamine decarboxylase inhibitor or COMT inhibitor to reduce these effects
  • Short half life – 50 to 90 mins
  • Rapidly absorbed from the proximal small intestine via the large neutral amino acid (LNAA) transport carrier system
38
Q

Patient information for l-dopa

A
  • Dyskinesia common
  • Reduced efficacy over time
  • Avoid abrupt withdrawal
39
Q

Dopamine Agonists examples

A

Rotigotine
Bromocriptine
Apoorphine
Pramipexole

40
Q

Mechanism of action of dopamine agonists

A

Dopamine agoinsts selective for the D2 receptor in the CNS

Inhibits the release of prolactin from the anterior pituitary gland

Duration longer than L-dopa

Stiulates post synaptic dopamine receptors

Apomorphine works also at D2 receptor- non selective

Pramipexole: selective D3 receptor

41
Q

Indication for dopamine agonists

A

Parkinsons disease

42
Q

Side effects of dopamine agonists

A

apopmorphine: pain at site of injection, nausea, vomitting

Pramipexole; hllucinations, nausea, drowiness, involuntary movements

43
Q

Important PD/PK of dopamine agonists

A

Apomorphine: highly emetic, hence limited use. Short half life (40 mins). Needs to be given via injection.
Pramipexole: Cimetidine increases its toxicity, long half life (8 hrs)
Dopamine Agonists have reduced efficacy over time

44
Q

Patient information for dopamine agonists

A

Apomorphine can only be injected

Dopamine agonists are weaker then L-DOPA so treatment may be modified in time.

45
Q

Catechola-o-methyl transferase inhibitor

A

Entacapone

46
Q

Mechanism of action of entacapone

A

Prevents the peripheral breakdown of levodopa by inhibiting COMT (COMT converts L-DOPA into 3-methoxy-4-hydroxy-L-phenylalanine (3-OMD). 3-OMD doesn’t cross the blood brain barrier).

Therefore more levodopa reaches the brain

47
Q

Indication of catechol-o =-methyl transferase inhibitor

A

Parkinson’s Disease in conjunction with L-DOPA and dopamine decarboxylase inhibitor

48
Q

Side effects of catechol-o-methyl transferase inhibitor

A 
Dyskinesia (common, up to 27%)
Nausea (11%)
Abdominal pain
Vomiting
Dry mouth
Dizziness
49
Q

Important PK/PD of catechol-o-methyl transferase inibitor

A

Rapidly absorbed

Levodopa dose may need to be reduced by 10-30% when given with Entacapone

50
Q

Patient information of catechol-methyl transferase inhibitor

A
  • Urine may turn brown – normal
  • Could become lightheaded/dizzy while doing daily activities
  • Avoid abrupt withdrawal
51
Q

Selegiline, rasagiline

A

MAO-B inhibitor

52
Q

Mechanism of action of selegiline, rasagiline

A
  • prevents dopamine breakdown by binding irreversibly to monoamine oxidase
  • can be prescribed as monotherapy in early disease or as adjunct in later disease
  • well tolerated

Neuro (16 decks)

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