Anticonvulsants

Question 1

Phenytoin

Answer 1

Drug of choice for initial therapy in adults.
Use: Partial Simple & Complex, and Generalized Tonic-Clonic (all oral). Emergency Tx for Generalized Status Epilepticus vi IV. Not for Absence seizures.
Mech: Blocks voltage gated Na & Ca channels & Ca
Pharm: slow absorption, fast distribution. Bound to plasma protein. Metabolized by Cyp450. Saturation @ 4-600mg/day.
Metab: Increases metabolism of Doxycycline, Cyclosporine. Carbamazepine stimulations Phenytoin metabolism. Chloramphenicol & Sulfonamide decrease metabolism

Question 2

Fosphenytoin

Answer 2

Prodrug of Phenytoin. IM or IV.
Drug of choice for initial therapy in adults.
Use: Partial Simple & Complex, and Generalized Tonic-Clonic (all oral). Emergency Tx for Generalized Status Epilepticus vi IV. Not for Absence seizures.
Mech: Blocks voltage gated Na & Ca channels & Ca
Pharm: slow absorption, fast distribution. Bound to plasma protein. Metabolized by Cyp450. Saturation @ 4-600mg/day.
Metab: Increases metabolism of Doxycycline, Cyclosporine. Carbamazepine stimulations Phenytoin metabolism. Chloramphenicol & Sulfonamide decrease metabolism

Question 3

Carbamazepine

Answer 3

Drug of choice for Partial Simple & Complex and Generalized Tonic-Clonic
Mech: blocks voltage gated Na channels.
Pharm: Oral, slow absorption, highly lipid soluble (brain), metabolized by Cyp450. INCREASES its OWN metabolism during chronic administration.
Metabolism inhibited by: Cimedidine, Diltiazem, Erythromycin, Isoniazid, Propoxyphene.

Question 4

Valproic Acid (Valproate)

Answer 4

Drug of choice for Generalized Myoclonic seizures. Second-line for treating Generalized Tonic-Clonic & Absence seizures.
Mech: block voltage gated Na & Ca channels; facilitates GABAergic synaptic transmission.
Pharm: Oral, rapidly absorbed. Plasma protein binding.
Metab: CYP450 Divalproex* is a combination of sodium valproate & valproic acid to improve GI tolerance.

Question 5

Ethosuximide

Answer 5

Drug of choice for absence seizures.
Mech: Blocks voltage gated T-type Ca channels.
Pharm: Orally, well-absorbed. Not bound to plasma proteins* Long half-life of 30-60 hours.
Metab: 75% metabolized by CYP450, 25% in urine.

Question 6

Phenobarbital

Answer 6

Barbiturate.
For Simple Partial & Generalized Tonic-Clonic seizures, and Febrile seizures in children.
Combine with Carbamazepine & Phenytoin to reduce dose.
Also used to treat anxiety
Mech: activation of GABA receptors to increase inhibitory tone
Pharm: Oral, well-absorbed, freely penetrates brain.
Metab: 75% by hepatic microsomal system.

Question 7

Primidone

Answer 7

Barbiturate.
For Simple Partial & Generalized Tonic-Clonic seizures, and Febrile seizures in children.
Combine with Carbamazepine & Phenytoin to reduce dose.
Also used to treat anxiety.
Mech: activation of GABA receptors to increase inhibitory tone. Therapeutic effect from metabolite - Phenobarbital.
Pharm: Oral, well-absorbed, freely penetrates brain.
Metab: 75% by hepatic microsomal system.

Question 8

Diazepam

Answer 8

Benzodiazepine.
Drug of choice to treat Generalized Status Epilepticus.
Also used to treat anxiety.
Mech: activation of GABA receptors.
AE: Tolerance after six months.

Question 9

Lorazepam

Answer 9

Benzodiazepine.
Drug of choice to treat Generalized Status Epilepticus.
Also used to treat anxiety.
Mech: activation of GABA receptors.
AE: Tolerance after six months.

Question 10

Lamotrigine

Answer 10

For Partial Simple & Complex and Generalized Tonic-Clonic seizures.
Mech: inhibits release of glutamate. Blocks voltage gated Na channels.
Metab: liver.
Interactions: half-life decreased by enzyme inducing drugs & increased by Valproic Acid

Question 11

Gabapentin

Answer 11

For Partial Simple & Complex and Generalized Tonic-Clonic
Mech: blocks Ca channels and the release of Glutamate. Enhances GABA transmission
Not metabolized - kidney elimination. Not bound to proteins.
Short half-life. Negligible drug interactions.

Question 12

Pregabalin

Answer 12

For Partial Simple & Complex

Blocks Ca channels

Question 13

Topiramate

Answer 13

For Partial Simple & Complex and Generalized Tonic-Clonic.
Blocks Na channels, increases PS GABA receptors.

Question 14

Levetiracetam

Answer 14

Broad Spectrum* for Partial and Generalized (Tonic-Clonic, Myoclonic)
Modifies Glutamate and GABA release; binds to synaptic protein SV2A.

Question 15

Generalized myoclonic seizures

Answer 15

Valproic acid. 2nd: Diazepam, Lorazepam, Levetiracem.

Question 16

Generalized absence seizures

Answer 16

Ethosuximide. 2nd: Diazepam, Lorazepam.

Question 17

Generalized febrile seizures in kids

Answer 17

Phenobarbital

Question 18

Generalized status epilepticus

Answer 18

Emergency Tx: Phenytoin IV

Drug of choice: Diazepam, Lorazepam (Benzodiazepine)