Classification of Seizure or Epilepsy—

Partial seizure—	§    Simplex §    Complex §    Partial seizure secondarily generalized
Generalized seizure—	§    Tonic-clonic (grand mal) §    Absence (petit mal)—children mostly §    Tonic §    Atonic §    Clonic and myoclonic §    Infantile spasms

Classification of Anti-Epileptic drugs—

Hydantoin group—	§    Phenytoin §    Mephenitoin
Iminostilbene group—	§    Carbamazepine §    Oxcarbazepine
Barbiturates and Benzodiazepines—	§    Phenobarbitone §    Mephobarbitone §    Diazepam	§    Clonazepam §    Lorazepam
Desoxybarbiturates—	§    Primidone
Valproic acid group—	§    Sodium Valproate

Anti-seizure drugs act by—

§    Blocking the Na⁺ channel

§    Blocking the Ca⁺⁺ channel

§    Blocking the excitatory neurotransmitters and ↑ the activity of inhibitory neurotransmitter (GABA)

*** cognitive function of the rain means the intelligence function of the brain

Principle of Mechanism of Action of Anti-Epileptic drugs—

In general, voltage dependent Na-channel enter an inactive state following each action potential. Prolongation of this inactive state with prolongation of the refractory period is the principle of mechanism of action of—

o  Phenytoin

o  Carbamazepine

o  Lamotrizine

o  Sodium Valproate

o  Topiramate

§    A low threshold calcium current govern oscillatory response in thalamic neuron. Some drugs like Ethosuccimide or Dimethadione cause low threshold of the calcium current.

§    Some drugs affect synaptic transmission. Drugs like Benzodiazepines, Barbiturates and possibly Topiramate enhances GABA mediated inhibition.

§    Some drugs like GABA Pentine, Vigabatrin acts by decreasing reuptake or decreasing metabolism of GABA.

§    Some drugs act on excitatory Glutamatergic neurotransmission, they block Glutamatergic AMPA receptor. Drugs of this group are Phenobarbitone, Topiramate.

§    Drugs like Rimacemide block the NMDA receptor. NMDA is N-methyl Daspertate, it is one of the subtype of glutamate and aspartate.

Note—strong stimulation of NMDA receptor lead to neuronal death and NMDA agonist can save the neuron from anoxia.

Comparison between Phenytoin and Carbamazepine—

Phenytoin	Carbamazepine
1. It is a Hydantoin group	1. It is an Iminostilbene group
2. Used in both generalized and partial epilepsy	2. Preferred drug in partial seizure but also highly effective in generalized seizure
3. After absorption about 95% is bound to plasma protein	3. About 70-75% is bound with plasma protein
4. It is available in oral and parenteral form	4. It is available only in oral form
5. Does not cause auto-induction of it’s metabolism	5. Causes auto-induction of its metabolism
6. The main mode of action of Phenytoin is to inhibit Na+ influx across neuronal cell membrane in epileptic foci	6. Mechanism of Action appears to be same as that of Phenytoin
7. Sedation occurs at considerably higher therapeutic dose	7. Usually not sedative in its therapeutic use
8. More risk of cognitive impairment	8. Least risk of cognitive impairment