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Pharmacology III > Anticonvulsants > Flashcards

Anticonvulsants Flashcards

1
Q

Anticonvulsant Mechanisms (GABA)

A

 Goal is to increase GABA activity

 Block GABA re-uptake -Tiagabine
 Inhibit GABA metabolism - Vigabatrin
 Stimulate GABAa receptors - Benzos and barbs
 Binds synaptic vesicular protein SV2A - Levetiracetam

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2
Q

Anticonvulsants Mechanism (Glutamate)

A

 The goal is to decrease excitatory glutamate activity
 Common targets: voltage-gated Na+and
Ca++ channels
• Phenytoin, ethosuximide

 Other targets: SV2A, K+channels, NMDA and AMPA
receptors

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3
Q

Phenytoin (Dilantin®); Fosphenytoin (Cerebyx®) - MoA

A

Prolongs inactivation of Na+channels; decreases glutamate activity

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4
Q

Phenytoin (Dilantin®); Fosphenytoin (Cerebyx®) - Uses

A

Partial seizures, generalized tonic-clonic seizures

• Not effective for absence seizures

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5
Q

Phenytoin (Dilantin®); Fosphenytoin (Cerebyx®) - Pharmacokinetics

A

•Not water soluble -> not injected
• Fosphenytoin (Cerebyx®) - injectable form
• Elimination is 1st order at low doses
• Zero order at therapeutic at higher doses; Small
changes in dose/elimination can cause big changes in
plasma levels

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6
Q

Phenytoin (Dilantin®) - Drug Interactions

A
  • Drugs that alter CYP450’s

* Metabolized by, induces, and inhibits CYP450’s

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7
Q

Phenytoin (Dilantin®) - Side Effects

A 
• Nystagmus, diplopia, ataxia, sedation 
• Gingival hyperplasia
• Long-term:
  Coarsening of facial features
  Mild peripheral neuropathy
  Abnormal Vitamin D metabolism
• Skin rash - discontinue use (risk of SJS)
• Pregnancy category D
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8
Q

Carbamazepine (Tegretol®) - MoA

A

• Blocks Na+channels; decreases glutamate activity
• Inhibits NE release and reuptake; May potentiate
GABA action

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9
Q

Carbamazepine (Tegretol®) - Uses

A
  • Drug of choice for partial seizures
  • Generalized tonic-clonic seizures
  • Bipolar disorder
  • Trigeminal Neuralgia
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10
Q

Carbamazepine (Tegretol®) - Pharmacokinetics

A
  • Induces CYP450’s (3A4);lots of drug interactions

* Induces own metabolism

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11
Q

Carbamazepine (Tegretol®) - Drug Interactions

A

• Increases metabolism of multiple anticonvulsants,
haloperidol and oral contraceptives
• Metabolism increased by: phenobarbital, phenytoin
• Metabolism inhibited by: cimetidine, fluoxetine,
valproic acid

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12
Q

Carbamazepine (Tegretol®) - Side Effects

A

• Diplopia, ataxia, GI upset, drowsiness
• Aplastic anemia and agranulocytosis
• Stevens Johnson Syndrome - More common in
patients with a certain HLA allele (HLA-B1502); should
be screened for HLA-B1502
• Pregnancy category D

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13
Q

Lamotrigine (Lamictal®) - MoA

A

• Inactivation of Na+channels; decreases glutamate
activity
• May also inhibit Ca++channels

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14
Q

Lamotrigine (Lamictal®) - Uses

A

• Partial seizures
• May be effective against myoclonic and absence
seizures in children
• Bipolar disorder

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15
Q

Lamotrigine (Lamictal®) - Pharmacokinetics

A

• Inducers of CYP450s (phenytoin, carbamazepine,
phenobarbital) will increase metabolism
• Half-life doubled by valproic acid

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16
Q

Lamotrigine (Lamictal®) - Side Effects

A

• CNS -Dizziness, headache, diplopia, ataxia, &
somnolence
• GI -nausea and vomiting
• Skin rash and Stevens-Johnson syndrome

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17
Q

Topiramate (Topamax®) - MoA

A
  • Blocks Na+channels; decreases glutamate activity

• Also has some activity at Ca2+ channels
• Potentiates GABA receptors and inhibits glutamate
receptor
• May inhibit spread of seizures

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18
Q

Topiramate (Topamax®) - Uses

A
  • Partial and generalized tonic-clonic seizures
  • May also be effective for absence seizures
  • Migraine prevention
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19
Q

Topiramate (Topamax®) - Pharmacokinetics

A

May increase metabolism of contraceptives

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20
Q

Topiramate (Topamax®) - Side Effects

A

Dizziness, sedation, nervousness, confusion

• Acute myopia/glaucoma

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21
Q

Levetiracetam (Keppra®) - MoA

A
  • Binds synaptic vesicular protein (SV2A)

• Appears to decrease glutamate and increase GABA
release

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22
Q

Levetiracetam (Keppra®) - Uses

A

Partial, myoclonic, and tonic-clonic

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23
Q

Levetiracetam (Keppra®) - Pharmacokinetics

A

• Oral absorption is rapid; peak blood concentrations in
1-2h
• ½ life of 6-8h; longer in elderly

Minimal drug interactions

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24
Q

Levetiracetam (Keppra®) - Side Effects

A

• Dizziness, somnolence, ataxia, and asthenia

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25
Q

Phenobarbital (Luminal®) - MoA

A
  • Prolongs opening of chloride channel at GABA receptor

* Alters Na+and Ca2+conductance at high concentrations

26
Q

Phenobarbital (Luminal®) - Uses

A
  • Partial seizures

* Generalized tonic-clonic seizures

27
Q

Phenobarbital (Luminal®) - Drug Interactions

A

Induction of CYP450’s increases metabolism of Phenytoin and carbamazepine

28
Q

Gabapentin (Neurontin®) - MoA

A

GABA analog; May augment GABA release

29
Q

Gabapentin (Neurontin®) - Uses

A

Adjunct for partial and generalized tonic-clonic seizures

  • Neuropathic pain
  • Bipolar disorder (off label)
30
Q

Gabapentin (Neurontin®) - Pharmacokinetics

A

• 1st order elimination; Excreted unchanged by the
kidney
• Short half-life, taken 3 times/day

31
Q

Gabapentin (Neurontin®) - Side Effects/Precautions

A

Sleepiness, dizziness, ataxia, fatigue, tremor, headache

Pregnancy Category C

32
Q

Gabapentin (Neurontin®) - Drug Interactions

A

Negligible

33
Q

Pregabalin (Lyrica®) - MoA

A

 GABA analog – structurally related to GABA
 Binds to alpha-2-delta subunit of voltage-gated
calcium channels inhibiting excitatory neurotransmitter
release

34
Q

Pregabalin (Lyrica®) - Uses

A

 Used for generalized anxiety disorder

 Other uses: neuropathic pain, fibromyalgia, post-
operative pain

35
Q

Pregabalin (Lyrica®) - Metabolism

A

negligible so little adverse drug interaction (relative to other anticonvulsants); ½ life about 6 hrs.

36
Q

Pregabalin (Lyrica®) - Side Effects

A

Peripheral edema, dizziness, fatigue, weight gain, xerostomia, ataxia, blurred vision, GI disturbances, etc.

37
Q

Pregabalin (Lyrica®) - Contraindications

A

Teratogenic

38
Q

Tiagabine (Gabitril®) - MoA

A

Inhibits reuptake of GABA (GAT-1); Enhances GABA activity

39
Q

Tiagabine (Gabitril®) - Uses

A

Adjunct treatment for partial seizures

40
Q

Tiagabine (Gabitril®) - Pharmacokinetics

A

• Short half-life (5-8h) which is shortened by CYP450
inducers

• Few drug interactions

41
Q

Tiagabine (Gabitril®) - Side Effects

A
  • Nervousness, difficulty concentrating, depression
  • Dizziness, tremor, rash (rare, but stop drug)
  • Pregnancy Category C
42
Q

Vigabatrin (Sabril®) - MoA

A

Irreversibly inhibits GABA transaminase (GABA-T); decreases GABA metabolism and enhances activity

43
Q

Vigabatrin (Sabril®) - Uses

A

Refractory complex partial seizures

• Infantile spasm (West’s syndrome)

44
Q

Vigabatrin (Sabril®) - Pharmacokinetics

A

½ life of 6-8h but drug effects are prolonged and do not correlate with plasma levels

45
Q

Vigabatrin (Sabril®) - Side Effects

A
  • Visual field problems/retinal damage

* Agitation, confusion

46
Q

Ethosuximide (Zarontin®) - MoA

A

• Inhibits low-threshold (T-type) Ca2+ channels
• Inhibits ‘pacemaker’ for rhythmic
cortical discharge

47
Q

Ethosuximide (Zarontin®) - Uses

A

Drug of choice for absence seizures

48
Q

Ethosuximide (Zarontin®) - Pharmacokinetics

A

Metabolized by liver

• Variable half-life of 18-72h

49
Q

Ethosuximide (Zarontin®) - Side Effects

A

GI irritation, lethargy, fatigue, headache, dizziness
• Hiccup
• Stevens Johnson syndrome very rare

50
Q

Ethosuximide (Zarontin®) - Drug Interactions

A

Metabolism inhibited by valproic acid

51
Q

Valproic acid (Depakene®) - MoA

A

Blocks Ca2+ channels and Na+channels

•May enhance GABA activity

52
Q

Valproic acid (Depakene®) - Uses

A

Absence and general tonic-clonic seizures (“mixed” seizures)
•Bipolar disorder
•Prophylaxis of migraine

53
Q

Valproic acid (Depakene®) - Pharmacokinetics

A
  • Absorption is prolonged by food; ½ life of 9-18h

* Inhibits its own metabolism at low doses

54
Q

Valproic acid (Depakene®) - Side Effects

A

Nausea, abdominal pain, heartburn, weight gain, sedation, tremor, alopecia

• Hepatotoxicity - Monitoring liver function is
recommended
• Pregnancy category D - Increased risk of Spina Bifida

55
Q

Valproicacid (Depakene®) - Drug Interactions

A

• Inhibits metabolism of phenytoin, phenobarbital,

carbamazepine

56
Q

Clonazepam (Klonopin®) - MoA

A
  • Benzodiazepine

Stimulates GABA receptor and enhances GABAergic inhibition

57
Q

Clonazepam (Klonopin®) - Uses

A

Absence seizures, myoclonic seizures and infantile spasms (West Syndrome)

58
Q

Clonazepam (Klonopin®) - Side Effects

A

Sedating –tolerance develops

  • Tolerance to anti-seizure effect may develop
  • Pregnancy category D
59
Q

Diazepam (Valium®) and Lorazepam (Ativan®) - Uses

A

Drug of choice for status epilepticus

60
Q

Diazepam (Valium®) and Lorazepam (Ativan®) - MoA

A

Stimulates GABA channel

61
Q

Diazepam (Valium®) and Lorazepam (Ativan®) - Pharmacokinetics

A

Administered IV or rectally

62
Q

Diazepam (Valium®) and Lorazepam (Ativan®) - Precuations

A

Pregnancy category D

Pharmacology III (10 decks)

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