Anticonvulsants Flashcards

1
Q

carbamazepine

A

Antiepileptic Drug
- Goal to prevent seizures while minimizing side-effects, by using simplest drug regimen

Mechanism:

  • Blocks abnormal voltage-gated channels
  • Blocks the Focal Epileptogenesis step in seizure

Alters ionic conductance to suppress firing of action potential:
- Inhibits voltage-activated Na channels to prolong the refractory period and reduce sustained firing

Causes drug interaction of Phenytoin:
- Stimulates Phenytonin Metabolism

Drug of choice for:

  • Partial simple
  • Partial complex
  • Tonic-clonic seziures
  • Use in: terminal Neuraliga, bipolar disorder

Oral administration

Slowly absorbed

HIGHLY LIPID SOLUBLE (rapid penetration to brain)

Metabolized by: p450 enzymes
- Induces p450 enzyme to increase it’s own metabolism
(10-15 hrs half life)

Drug Interactions:
- Enhance p450 system so increases metabolism of antiepileptics (phenytoin)

Metabolism is inhibited by several drugs:

  • Cimetidine
  • Diltiazem
  • Erythromycin
  • Isoniazid
  • Propoxyphene

Can be used with barbiturates for simple partial and tonic-clonic seiaures and febrile seizures in children

Hepatotoxicity

Common Side Effects:

  • Drowsiness/sedation
  • Ataxia
  • Nausea/Vomiting
  • Skin rash
  • Metabolic changes: weight gain/weight loss

Teratogenic Effects

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2
Q

ethosuximid

A

Antiepileptic Drug

Inhibits voltage-activated Ca2+ channels and thus inhibits rhythmic activity
= T type

Treat: ABSENCE SEIZURES

Pharmacokinetics:

  • Well absorbed orally
  • Not bound to Plasma Proteins
  • Long half life (30-60hr)
  • 75% metabolized by hepatic enzymes (p450)
  • 25% excreted in urine
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3
Q

gabapentin

A

Antiepileptic drug therapy

Treatment of simple or complex partial seizures

Generalized tonic-clonic seziures

Blocks Ca channels (binding to a2-delta subunit)

Releases glutamate

Enhances GABAergic synaptic transmission

Not metabolized/ does not include hepatic enzymes

Not bound to plasma proteins

Short half-life (5-8hrs)

Elimination by kidneys

Negligible drug interactions

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4
Q

lamotrigine

A

Antiepileptic Drug
- Goal to prevent seizures while minimizing side-effects, by using simplest drug regimen

Alters ionic conductance to suppress firing of action potential:
- Inhibits voltage-activated Na channels to prolong the refractory period and reduce sustained firing

Treatment:

  • Simple
  • Complex Partial
  • Tonic-clonic

Inhibits release of glutamate (suppresses excitatory tone)

Blocks voltage-activated Na channels (prevents repetitive firing)

Metabolized by liver

Drug interaction: half-life time of lamotrigine decreased by enzyme inducing drugs (carbamazepine, phenytoin) and is increased by valproic acid

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5
Q

phenobarbital

A

Barbiturate but part of antiepileptic drug therapy also

Works on abnormal ligand-gated channels

Steps in Seizures:

  • Focal Epileptogenesis
  • Synchronization

Enhances inhibitory GABAerigc neurotransmission

Works on:

  • Simple Partial
  • Recurrent tonic-clonic seizures
  • Febrile seizures in children

Faciliates GABA receptors to increase inhibitory tone

Pharmacokinetics

  • Well absorbed orally
  • Freely penetrates brain
  • 75% inactivated by hepatic microsomal system
  • Metabolite of primidone also

Teratogenic

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6
Q

phenytoin

A

Antiepileptic Drug
- Goal to prevent seizures while minimizing side-effects, by using simplest drug regimen

Mechanism:

  • Blocks abnormal voltage-gated channels
  • Blocks the Focal Epileptogenesis step in seizure

Alters ionic conductance to suppress firing of action potential:
- Inhibits voltage-activated Na channels to prolong the refractory period and reduce sustained firing

Status epilepticus:
- Use IV administration of this long acting drug to keep effects on

Drug of choice for Initial Therapy of Epilepsy in Adults
- Effective for:
Partial Simple
Partial complex
Tonic-clonic

Emergency treatment for Status Epilepticus

NOT USED in ABSENCE SEIZURES

Mechanism:

  • Blocks Na channels
  • Suppresses repetitive action potential firing
  • Blocks voltage activated Ca channels

Pharmacokinetics:

  • Oral administratino for chronic
  • IV for emergency
  • Oral absorption slow but distribution is rapid, brain conc is high
  • High plasma protein binding (90%)
  • 95% is metabolized by p450 system (CYP2C9) and CYP2C19, so can become SATURATED at high dosage (400-600mg)
  • Less than 5% is unchanged and excreted by kidneys

Fosphenytoin is prodrug and is rapidly converted to phenytoin
- USED IM and IV

Drug Interactions: Enhances p450 system, increases metabolism of other drugs, doxycycline, cyclosporine

Drugs that stimulate Phenytoin Metabolism: CARBAMAZEPINE

Drugs that inhibit phenytoin metabolism: CHLORAMPHENICOL, SULFONAMIDE

Side Effect:

  • Drowsiness, sedation
  • Ataxia
  • Nausea and vomiting
  • Skin Rash
  • Metabolic changes

Additional:

  • GINGIVAL HYPERPLASIA
  • MEGALOBLASTIC ANEMIA
  • TERATOGENIC EFFECT
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7
Q

valproic acid

A

Antiepileptic Drug

Inhibits voltage activated Na channels and thus prolong the refractory period and reduce sustained firing

Inhibits voltage-gated Ca2+ channels and thus inhibits rhytmic activity

Enhance inhibitory GABAergic neurotransmission

Drug of choice for:

  • Myoclonic seizures
  • Second line drug for tonic-clonic and absence seizures (due to hepatotoxicity)

Mechanism:

  • Blocks Na and Ca channels and faciliates GABA synpatic transmission
  • Reduces propagation of abnormal electrical discharge in brain

Pharmacokinetics:

  • Orally effective/rapidly absrobed
  • High level of Plasma Protein binding (90%)
  • Metabolized by p450
  • Divalproex is combination of Sodium valproate and valproic acid
  • Improves GI tolerance

Side Effects:

  • Hepatotoxic
  • Thrombocytopenia
  • Teratogenic Effects
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8
Q

pregabalin

A

New class of Antiepileptic Drug

Blocks Ca channel (via a2-delta subunit) and blocks release of glutamate

Used for:

  • Simple
  • Complex Partial seizures

Side Effects:
- Thrombocytopenia

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9
Q

topiramate

A

New class of antiepileptic drug

  • Block Na channel
  • Increases activity of postsynatpic GABA receptors

Used for:

  • Simple
  • Complex partial seizures
  • Generalized tonic-clonic seizures
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10
Q

levetiracetam

A

Antiepileptic Drug Therapy

  • Modifies glutamate and GABA release via binding to synaptic protein SV2A
  • Adjunctive treatment of:
  • Simple
  • Complex partial
  • Generalized tonic-clonic
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11
Q

clonazepam

A

Benzodiazepine that enhances GABAergic transmission for treatment of seizures

Treat:

  • Myoclonic
  • Absence seizures
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12
Q

diazepam

A

Antiepileptic Drug/Benzodiazepine

Rapid acting antiepileptic that might useful for direct treatment of status epilepticus

Drug of choice for:
Acute emergency treatment of Status Epilepticus

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13
Q

lorazepam

A

Antiepileptic Drug/Benzodiazepine

Rapid acting antiepileptic that might useful for direct treatment of status epilepticus

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