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Neurobiology 2 - M2 > 10 21 2014 Anti-epileptic drugs > Flashcards

10 21 2014 Anti-epileptic drugs Flashcards

1
Q

what are the mechanisms by which anti-seizure drugs try to work

A
  1. Increase GABA
  2. Decrease Glutamate release from pre-synaptic vessel or signaling at post-synaptic ( AMP receptors)
  3. Decrease frequency of Na+, Ca2+ voltage gated channels
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2
Q

What drugs are used for partial seizures (simple and complex)

A
  1. Carbamazepine
  2. Phenytoin
  3. Valproate

NEW DRUGS: all of them

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3
Q

What drugs are used for Partial with secondarily generated tonic-clonic seizures?

A
  1. Carbamazepine
  2. phenytoin
  3. valproate
  4. Primidone

NEW Drugs: ALL of them

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4
Q

Drugs used to treat absence seizure

A
  1. Ethosuximide
  2. Valproate
  3. clonazepam

NEw Drug: Lamotrigine

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5
Q

Drugs used to treat Myoclonic seizures

A
  1. Valproate
  2. Clonazepam

New Drug: Levetiracetam

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6
Q

Drugs used in Tonic- Clonic seizures

A
  1. Carbamazepine
  2. Phenobarbital
  3. Phenytoin
  4. Primidone
  5. Valproate

NEW DRugs: Lamotrigine, Levetiracetam, Topiramate

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7
Q

Drugs used in status epilepticus

A
  1. Phenobartital

2. Diazepam

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8
Q

Mechanism of Action of Phenytoin

A
  1. block voltage gated Na+ (presynaptic) inactive phase
  2. Reduces K+ and Ca2+ = changes membrane potential

= Inhibits release of Glutamate and increases release of GABA

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9
Q

Pharmacokinetics of Phenytoin

  1. Delivery
  2. Bind to plasma?
  3. where is it metabolized?
A
  • oral, IV, IM (intramuscular)
  • 90% bind to plasma
  • Liver to inactive metabolites and excreted in urine
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10
Q

Drug interactions of Phenytoin

A
  • Valproate competes for protein binding sites and inhibits phenytoin metabolism
  • induce microsomal enzymes responsible for metabolism of many drugs
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11
Q

Toxicity of Phenytoin

A

Diplopia, ataxia, gingival hyperplasia (face), hirsutism, neuropathy, nystagmus.
Sedation at really high levels.
Sedation at really high levels.

  • LONG TERM TOXICITIES
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12
Q

Mechanism of Carbamazepine

A

Structure is similar to tricylic-antidepressants

  • decrease Na+ current (voltage gated)
  • decrease release of glutamate
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13
Q

Pharmacokinetics of Carbamazepine

  1. delivery
  2. metabolism
A

given orally

induces it own metabolism P450 enzymes (CYP2C, CYP3A, UGT)

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14
Q

Drug Interactions of Carbamazepine

A
  • Phenobarbital, Phenytoin, Valproate increase metabolism of Carbamazepine.
  • may enhance transformation of Phenytoin
  • may lower concentration of other anti-seizure drugs
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15
Q

Toxicity of Cabamazepine

A

Drowsiness, blurred vision, diplopia, headache, dizziness, ataxia, nausea and vomiting.

  • cognitive effects can interfere with learning
  • hyponatremia
  • Stevens- Johnson Syndrome: rare disorder in skin and mucosa
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16
Q

Mechanism of Valproic Acid ( Valproate)

A
  1. prolongues inactivation of voltage gated Na+
  2. blocks T-type Ca2+ receptors
    = Increases GABA release
    = inhibits tonic hind limb extension during maximal electroshock seizures
17
Q

Pharmacokinetics of Valproic Acid

  1. delivery and rate of absorption
  2. Bind to proteins?
  3. Where and what enzyme(s) help with metabolism
A
  • Absorbed rapidly and completely after oral
    - can also be given IV
  • 90% binds to plasma proteins
  • T1/2 = 15hrs
  • Hepatic metabolism via UGT enzymes
18
Q

Drug interactions of Valproate

A

inhibits metabolism of phenytoin, phenobarbital, lamotrigine an lorazepam

  • can displace other drugs from albumin (ex phenytoin)
19
Q

Undesirable effect of Valproate

A

causes severe/ fatal hepatic toxicity in children

20
Q

Mechanism of Ethosuximide

A

blocks T-Type Ca2+
- this is the pacemaker current for thalamic neurons that are responsible for generating rhythmic cortical discharge of an absence attack

21
Q

Drug interactions of Ethosuximide

A

Valproic acid decreases ethosuximide clearance and higher stead-state concentrations owing to inhibition of metabolism

22
Q

Toxicity of Ethosuximide

A

GI: pain, n/v
lethargy, fatigue
Headache, dizziness, hiccups, and euphoria
Stevens-Johnson sundrome

23
Q

Mechanism of Phenobarbital

A

blocks Na+, Ca 2+

- allosteric regulation of GABAa receptor : ENHANCES GABA current and DECREASES GLUTAMATE

24
Q

Pharmcokinetics of Phenobarbital

A
  • Oral: complete but slow, very long half life (can also be delivered IV)
  • 40-60% is bound by plasma proteins
  • 25% is eliminated by kidneys
  • inactivated by hepatic microsomal enzymes (CYP2C9)
  • also induces UGT enzymes
25
Q

Drug interactions of Phenobarbital

A

Induces metabolism of many drugs

26
Q

Toxicity of Phenobarbital

A

Sedation, Nystagmus, ataxia, irritability and hyperactivity in children and agitation in elderly
rahs
Hypoprothormbinemia w/ hemorrhage (newborns whose mom took drug)

Megaloblastic anemia

27
Q

Considerations for long term use:

A
  1. drug resistance
  2. poor absorption/ rapid metabolism – low levels in blood
  3. inhibit drug metabolism

Don’t use phenytoin as a long term drug– terotogenicity

Neurobiology 2 - M2 (12 decks)

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