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30 Cards in this Set
- Front
- Back
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What are the 2 drugs used mainly for generalized absence seizures?
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-Ethosuximide
-Valproic acid |
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What are absence seizures?
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Momentary losses of consciousness
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In what patients are absence seizures typically seen?
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Children
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So what is a choice drug for treatment of absence seizures?
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Ethosuximide
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In what screening test would Ethosuximide be active?
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The chemical test (Not the electroshock test)
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What is the mechanism of action of Ethosuximide?
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Reduces T-type low-threshold Calcium currents in thalamic neurons.
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What additional mechanism does Ethosuximide have at concentrations much higher than therapeutic levels?
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Inibits Na/K ATPase
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So the 2 mechanisms of action of Ethosuximide are:
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-Reduction in low-threshold Ca currents in thalamic neurons
-Inhibition of Na/K ATPase at high concentrations |
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What are the 4 good pharmacokinetic properties of Ethosuximide?
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-Well absorbed orally
-Not protein bound -vol of distribution = total body water -Long halflife |
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What is the half life of Ethosuximide?
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Long - ~40 hrs
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What is a good thing about Ethosuximide's long halflife?
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You could just give it once a day
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What is a bad thing about giving Ethosuximide all in one dose, once a day?
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It causes gastric distress that is intolerable at these levels.
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What are 2 side effects of Ethosuximide?
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-Gastric distress
-Lethargy/fatigue |
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How can you ameliorate the gastric distress seen with Ethosuximide?
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By dosing 2x per day
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How is Ethosuximide metabolized?
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By the liver
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What drug DECREASES the liver metabolism of Ethosuximide? What drugs INCREASE it?
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Decrease: Valproic acid
Increase: Phenobarbital and Carbamazepine |
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What is an alternative drug to Ethosuximide for absence seizures?
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Valproic acid
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What kind of structure is Valproic acid?
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A carboxylic acid
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What are 3 mechanisms of action of Valproic Acid?
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-Increases GABA concentration
-Blocks repetitive neuronal firing -May reduce T-type Ca currents |
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So in what screening tests is Valproic acid active?
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BOTH! the Electroconvulsive shock test, and the chemical test
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So what seizures can be treated with Valproic acid?
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All of them!
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So what are 3 antiseizure meds that we know inhibit repetitive neuronal firing?
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PVC PIPES
-Phenytoin -Carbamazepine -Valproic acid |
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What are the 4 major pharmacokinetic points to remember about Valproic acid?
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-Well absorbed orally
-Bound to plasma proteins -Distributes in ECF -Inhibits metabolism of 3 drugs |
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What are the 3 drugs that Valproic acid inhibits the metabolism of?
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-Phenobarbital
-Phenytoin -Carbamazepine |
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What does Valproic acid compete with for protein binding?
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Phenytoin
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What are the 4 clinical uses of Valproic acid?
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-Absence seizures
-Absence seizures with concomtnt generalized tonic-clonics -Generalized tonic-clonics and partial seizures -Myoclonic seizures |
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What are Myoclonic seizures again?
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Jerky motions that are very difficult to treat
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What are 3 dose-related side effects of Valproic acid?
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-GI upset
-weight gain -hair loss you become a fat bald person with upset stomach |
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What are 2 non-dose related side effects of Valproic acid?
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-Hepatotoxicity
-Teratogenicity |
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What teratogenic defect does Valproic acid cause?
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Spina bifida - neural tube defects
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