Anticonvulsants II Flashcards by tcarlso 3

What are the general adverse side effects of antiepileptic drugs?

Ataxia
Nystagmus
HA
Depression
Sedation

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How are antiepileptic drugs metabolized?

hepatic MES system

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Abrupt withdrawal of antiepileptic drugs has the potential for what to happen?

Inducing seizures

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Why do antiepileptics cause a decrease in efficacy of oral contraceptives?

Induces cytochrome p450

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What is the safest antiepileptic drug to take during pregnancy?

Phenobarbital

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What is the MOA of hydantoins? (3)

Blocks and prolongs the inactivated state of voltage-gated Na channels
Decreases glutamate release
Enhances GABA release

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What type of antiepileptic drug is phenytoin?

Hydantoin

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What type of antiepileptic drug is Fosphenytoin?

Hydantoin

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What is the major difference between the Hydantoins Phenytoin and fosphenytoin?

Fosphenytoin is more soluble prodrug

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What are the pharmacokinetics of Hydantoins (absorption, state in blood, what type of elimination)?

Variable absorption
Highly bound to protein albumin
Zero order elimination

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What type of drugs cause the release of albumin bound hydantoins?

Acidic drugs

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What is the route of metabolism for Hydantoins?

Metabolized in liver by MES system

Induction of p450 enzymes

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Can zero order elimination be saturated?

yes

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At low doses, what is the relationship between plasma concentration, and dose? High doses?

Low = relatively linear
High = Nonlinear

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true or false: phenytoin can be used to treat status epilepticus

true

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What are the idiosyncratic side effects of phenytoin?

Gingival hyperplasia
Osteomalacia
Hirsutism

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What is fetal hydantoin syndrome?

Teratogenic effects like cleft palate,

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What are the two drugs that interfere with Phenytoin metabolism?

Warfarin

barbiturates (high concentration)

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What are the two drugs that increase phenytoin metabolism?

Barbituates (low dose)

Carbamazepine

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Lower pH can cause the release of phenytoin from albumin. What are the two drugs and one condition that can cause this?

ASA
Valproic acid
Renal failure

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What is the MA of carbamazepine?

Inhibition of voltage gated Na channels

Decreases E release

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How is carbamazepine metabolized?

Hepatic MES

Potent induce of MES p450s

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How well is carbamazepine absorbed?

Well absorbed

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What is the MOA of oxcarbazepine?

Derivative of carbamazepine

Inhibits Na channels and decreases E release

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What is the major difference between Oxcarbazepine and carbamazepine?

fewer drug interactions

What are the clinical uses of carbamazepine?

generalized szs Partial szs Trigeminal neuralgia

What are the side effects of carbamazepine?

CNS depression Aplastic anemia SIADH

What are the three major drug interactions of carbamazepine?

Phenytoin valproate Phenobarbital

What is the role of carbamazepine in the treatment of bipolar disorder?

treats the manic phase

What is the MOA of barbiturates?

Enhances phasic GABA(A) receptor responses, increasing the opening time of Cl channels

What are the primary uses of phenobarbital?

Status epilepticus | Neonatal seizures

What type of drug is phenobarbital?

Barbiturate

What type of drug is primidone?

Barbiturate

What is the MOA of ethosuximide?

Blocks presynaptic Ca influx through type T channels (decreases low threshold Ca currents), thereby blocking high frequency firing of neurons

How is ethosuximide metabolized?

Hepatic MES

What is the major clinical use of ethosuximide?

Absence seizures

What are the primary drugs to treat petit mal seizures?

Ethosuximide | valproic acid

What is the MOA of valproic acid?

Inhibition of Presynaptic T-type Ca Channels Inhibition of GABA transaminas

What are the two primary adverse effects of valproic acid?

``` hepatotoxic syndrome Teratogenic risk (spina bifida) ```

What is the role of valproic acid in bipolar disorder?

treats manic phase

What is the MOA of benzodiazepines?

Potentiates GABA-A responses by increasing the frequency of channel opening

What type of drug is diazepam?

Benzo

What type of drug is lorazepam?

Benzo

What is the preferred initial agent for status epilepticus?

Diazepam

What are the limitations of diazepam use?

Sedative effects | Tolerance

Why must diazepam be followed up by another antiepileptic in the treatment of status epilepticus? What other benzodiazepine can be used to avoid having to use two drugs?

Short duration of effect Lorazepam

What is the MOA of gabapentin?

Analog of GABA, thereby blocking presynaptic voltage gated Ca channel

What are the three major clinical uses of gabapentin?

1. generalized tonic-clonic seizures 2. Partial seizure 3. Neuropathic pain

What is the MOA of pregabalin?

GABA analog, blocking presynaptic Ca channels

What are the two drugs discussed that can treat neuropathic pain?

gabapentin | carbamazepine

What is the MOA of Lamotrigine?

Blocks presynaptic Na and Ca channels

What is the major adverse effect of Lamotrigine?

Steven-Johnson syndrome

what are the two major drugs that can interact with Lamotrigine?

Valproate | carbamazepine

What is Steven-Johnson syndrome?

a form of toxic epidermal necrolysis, starting with a sore throat and fever. Caused by hypersensitivity to a drug.

What is the MOA of felbamate?

Blocks Na channels and Glutamate receptors

What is the MOA of topiramate?

Blocks Na and Ca channels Potentiates GABA

What is the MOA of tiagabine?

Specific inhibitor of GABA reuptake

What is spasticity?

An exaggerated muscle stretch reflex syndrome that occurs following injury to the CNS

What is a spasm?

increase in muscle tension seen after certain MS injuries an inflammation

What is the cause of spasms/spasticity?

hyperexcitability of the neurons or muscle cells

What is the goal of pharmacotherapy in treating muscle spams/spasticity?

Normalize muscle excitatbility

What is the MOA of Baclophen?

GABA-B agonist

What is the neurotransmitter used in inhibitory interneurons?

GABA

What is the difference between GABA-A and GABA-B receptors?

``` A = ionic B = G protein coupled receptor ```

What is baclofen used for?

reduce spasticity of muscles

What can diazepam be used for, besides anticonvulsants?

treating muscle spasms

What are the 5 major cyclic ureides?

``` Phenytoin Fosphenytoin Primidone Phenobarbital Ethosuximide ```

What are the two major tricyclic antiepileptics?

Carbamazepine | Oxcarbazepine

What are the three major benzodiazepine antiepileptics?

Diazepam Lorazepam Clonazepam

What are the three major GABA derivative antiepileptics?

Gabapentin Pregabalin Vigabatrin

What is the MOA of acetazolamide?

carbonic hydrase inhibitor