Anti-Epileptics

Question 1

Phenobarbitone MOA

Answer 1

MOA
- Synaptic inhibition by GABAa action
- Prolong GABAa channel opening
AT HIGHER LEVELS
- Limit sustained repetitive firing of neurons through an action on Na+ Conductance
- Inhibits some Ca2+ currents

Question 2

Phenobarbitone Toxicity and Use

Answer 2

TOXICITY
- Sedation, Ataxia, Nystagmus, Rashes, Megaloblastic Anemia, Osteomalacia
USE
- GTC, Simple/Complex Partial, Status Epilepticus

Question 3

Phenytoin MOA and Pharmacokinetics

Answer 3

MOA
- INC Frequency firing of APs
- Slows rate of recovery of voltage gated Na+ channels from inactivation
PHARMACOKINETICS
- Metabolism is capacity limited (Saturation)

Question 4

Phenytoin SE, Drug Interactions, Uses

Answer 4

SE
- AT THERAPEUTIC LEVELS: Gum hypertrophy, Hirsutism, coarse facial features, acne, Rashes, DLE, Lymphadenopathy, Megaloblastic anemia, Osteomalacia, Fetal Hydantoin Syndrome
- HIGH PLASMA LEVELS: Ataxia, nystagmus, Diploplia, Vertigo
DRUG INTERACTIONS
- Induce enzymes which metabolize other drugs
USES
- GTC, Simple/Complex partial seizures, Status Epilepticus, Trigeminal Neuralgia

Question 5

Carbamazepine MOA and SE

Answer 5

MOA
- Inhibits frequent repetitive firing by prolonging Na+ Inactivation
SE
- Vertigo, Diploplia, Ataxia
- Drowsiness in Higher Doses
- Hyponatremia and water intoxication
- Agranulocytosis

Question 6

Carbamazepine Uses and Alternative

Answer 6

USES

• Most Effective drug for CPS
• DoC for GTC and SPS
• Trigeminal Myalgia
• MDP, Acute Mania
• *Oxcarbazepine
• Less potent
• Shorter duration of action
• Better Toxicity profile

Question 7

Felbamate MOA, SE, Use

Answer 7

MOA - Block NMDA
SE - Aplastic Anemia, Severe Hepatitis
Use - Third Line Drug for refractory PS

Question 8

Ethosuximide MOA, Toxicity, Use

Answer 8

MOA - Selectively inhibits T Type Ca2+ current
Toxicity - GI distress, Lethargy, Fatigue, Hypersensitivity
Use - Absence seizures

Question 9

Valproic Acid MOA, Toxicity, Use

Answer 9

MOA - Inhibits repetitive firing by blocking T Type Ca2+, INC GABA
Toxicity - Transient GI problems, Alopecia, Hepatitis, NTDs
Use - Absence seizures, Adjuvant for GTC CPS SPS, Myoclonic and Atonic Seizures, MDP and mania

Question 10

Diazepam

Answer 10

• Emergency control of convulsions

Question 11

Clonazepam

Answer 11

• Used in Absence seizures, sometimes myoclonic seizures and infantile spasms
• Sedation is prominent

Question 12

Gabapentin/Pregabalin

Answer 12

• GABA analog
• Add on for GTC and Partial
• Also used in neuropathic pain

Question 13

Lamotrigine

Answer 13

• Blocks Na+ channels and prevents release of excitatory NTs
• Add On: Refractory and secondary cases of Generalized seizures
• SJ Syndrome

Question 14

Vigabatrin

Answer 14

• Inhibitor of GABA transaminase
• Add on: Refractory cases of partial seizures
• Visual Disturbances may develop

Question 15

Tiagabine

Answer 15

• Inhibitor of GABA reuptake

- Adjuvant in PS

Question 16

Zonisamide

Answer 16

• Acts on Na+ Channel

- GTC and PS

Question 17

Levetiracetam

Answer 17

• PS

Question 18

Topiramate

Answer 18

• Blocks Repetitive Firing
• GTC and Partial
• Lennox Gestaut Syndrome