Anticonvulsants

Question 1

Phenytoin

Answer 1

Hydantoin Anticonvulsant
MOA: Blocks and prolongs inactivated state of Na channels; enhances release of GABA; prevents seizure propagation

Rx: tonic-clonic seisures, partial seizures, status epilepticus

Zero-order kinetics

Highly protein bound

SE: Gingival Hyperplasia, hirsutism

Question 2

Fos-phenytoin

Answer 2

newer, more soluble prodrug of phenytoin used for parenteral routes

Question 3

Carbamazepine

Answer 3

Tricyclic Anticonvulsant
MOA: inhibition of voltage-gated Na channels

Rx: Clonic-tonic seizures, partial seizures, Trigeminal neuralgia

SE: Syndrome of inappropriate ADH secretion

Question 4

Oxacarbazepine

Answer 4

Newer drug, similar to carbamazepine

Shorter half-life, active metabolite w/ longer duration and fewer drug interactions

Question 5

Phenobarbital

Answer 5

Barbiturate
MOA: enhances duration of GABA-A receptor response

Rx: Status epilepticus (and many other seizures)

Safe drug for seizures in pregnancy

Question 6

Primidone

Answer 6

metabolized by liver to phenobarbital

Question 7

Ethosuximide

Answer 7

Anticonvulsant
MOA: blocks presynaptic T-type Ca channels (blocks high-frequency firing of neurons)

Rx: Absence seizures (petit mal)

Question 8

Valproic acid

Answer 8

Anticonvulsant
MOA: inhibition of presynaptic T-type Ca channels (blocks neuronal firing); inhibition of GABA transaminase

Rx:absence seizures (petit mal)

SE: hepatotoxic sydrome, teratogenic risk

Question 9

Diazepam

Answer 9

Benzodiazepine / Muscle Relaxant
MOA: potentiates GABA-A responses by increasing the frequency of channel opening / increases central inhibitory actions of GABA on alpha motor neurons

Rx: status epilepticus

SE: sedation, tolerance

(short acting, must add another drug to avoid seizures recurrence)

Question 10

Lorazepam

Answer 10

Benzodiazepine
MOA: potentiates GABA-A responses by increasing the frequency of channel opening

Rx: status epilepticus

SE: sedation, tolerance

(longer duration of stopping seizure; can be used by itself)

Question 11

Gabapentin

Answer 11

GABA analog
MOA: blocks presynaptic Ca channels

Rx: Generalized tonic-clonic seizures, partial seizures, neuropathic pain (postherpetic neuralgia, fibromyalgia)

Question 12

Pregabalin

Answer 12

GABA analog

similar to gabapentin

Question 13

Lamotrigine

Answer 13

Carbamazepine analog
MOA: blocks presynaptic Na and Ca channels

Rx: partial seizures, generalized seizures

SE: Stevens-Johnson syndrome

Question 14

Felbamate

Answer 14

Anticonvulsant
MOA: block Na channels and glutamate receptors

adjunct Tx

Question 15

Topiramate

Answer 15

Anticonvulsant

SE: sedation, confusion, anorexia, paresthesias

Question 16

Tiagabine

Answer 16

Anticonvulsant
MOA: inhibitor of GABA uptake

Rx: partial seizures

SE: sedation, dizziness, headache, tremor

Question 17

Baclofen

Answer 17

Muscle Relaxant
MOA: GABA-B receptor agonist (↑ K conductance, hyperpolarization, ↓ Ca influx, ↓ excitatory transmitter release)

Reduces spasticity w/ MS, spinal & brain injury

causes less sedation than diazepam