Anticonvulsants part 2

Question 1

Phenytoin

Answer 1

absorption varies depending on formulation. Poorly soluble in aqueous. The original drug

Question 2

Fosphenytoin

Answer 2

dissolves easier than phenytoin. converted into phenytoin

Question 3

Phenytoin pharmacokinetics

Answer 3

Dose dependent (zero order). Can be saturated.

Question 4

Phenytoin mech of action

Answer 4

1. blocks and prolongs the inactivated state of voltage gate Na channels
2. enhances release of GABA
3. Prevents seizure propagation

Question 5

Phenytoin side effects

Answer 5

Gingival hyperplasia is the big one

fetal hydantoin syndrome

Question 6

Phenytoin clinical use

Answer 6

kkkd

Question 7

Carbamazepine mech of action

Answer 7

similar to phenyotoin-inhibition of voltage gated Na channels

Question 8

Carbamazepine metabolism

Answer 8

Potent inducer of P450s and its own metabolism

Question 9

Oxacarbazepine

Answer 9

Newer, similar to carbamazepine. Shortr half life, active metabolite has longer duration and FEWER drug interactions

Question 10

Carbamazepine clinical use

Answer 10

1. General clonic tonic seizures
2. Partial seizures
3. Trigeminal neuralgia-drug of choice
4. Manic phase of bipolar disorder

Question 11

Carbamazepine side effect

Answer 11

SIADH-Syndrome of Inappropriate ADH secretion.

Teratogenic-cleft palate and spina bifida

Question 12

Phenobarbital mech of action

Answer 12

Enhances phasic GABA receptor responses-increases opening time of Cl channel

Question 13

Phenobarbital clinical use

Answer 13

1. Neonatal seizures

2. Status epilepticus

Question 14

Primidone

Answer 14

Metabolized by liver to phenobarbital

Question 15

Ethosuximide

Answer 15

Pure petit mal drug

Question 16

Ethosuximide mech of action

Answer 16

blocks presynaptic T type Ca channels—>blocks high frequency firing of neurons

Question 17

Valproic acid

Answer 17

Inhibition of presynaptic T cell Ca channels —> blocks neuronal firing
inhibition of GABA transaminase

Question 18

Valproic acid clinical use

Answer 18

Absense of seizures (petit mal) drug of choice

Question 19

Valproic acid adverse effects

Answer 19

Hepatotoxic syndrome
Not meant for kids under 5
Teratogenic risk

Question 20

Diazepam

Answer 20

Initial agent for status epilepticus

Question 21

Diazepam mech of action

Answer 21

Potentiates GABAa responses by increasing frequency of channel opening

Question 22

Diazepam clinical use

Answer 22

Status epilepticus. Shorter acting, give with another drug like phenytoin

Question 23

Lorazepam

Answer 23

Longer duration of action than diazepam, so can be used alone

Question 24

Gabapentin

Answer 24

analog of GABA

Question 25

Gabapentin mech of action

Answer 25

block presynaptic voltage gated Ca channels

Question 26

Gabapentin clinical use

Answer 26

1. generalized grand mal 2. partial seizures 3. Neuropathic pain-postherpetic neuralgia and fibromyalgia

Question 27

Lamotrigine side effect

Answer 27

Stevens Johnson syndrome.

Question 28

Diazepam mech of action

Answer 28

Increases the central inhibitory actions of GABA on alpha motor neurons in spinal cord

Question 29

Baclofen mech of action

Answer 29

GABAb receptor agonist- increased K conductance, hyperpolarization, reduction in Ca influx, reduction in excitatory transmitter release. reduces spasticity with MS, spinal and brain injury As effective as diazepam, but causes less sedation