Antiepileptics

EPILEPSY

A group of CNS disorders characterized by paroxysmal cerebral dysrrhythmia with loss of consciousness with/ without convulsions [seizures] & sensory / psychiatric phenomena

Classification

General seizures:

1. General tonic clonic or Grand mal, 2.Absence 3. Atonic 4.Myoclonic 5.Infantile spasms

Partial Seizures:

1. Simple 2. Complex 3. Simple or Complex P Seizures

Secondarily generalized

Generalized seizures

1. General Tonic Clonic: [GTC] major epilepsy, Grandmal]: Commonest, 1-2 min; Sequence: Aura – cry – unconsciousness –tonic spasm – clonic jerking – prolonged sleep /CNS Depression

2. Absence Seizures: [minor epilepsy, petit mal]. More in children: momentary loss of consciousness, apparent freezing & staring; no movements; ½ min

3. Atonic siezures: [Akinetic Epilepsy]. Consciousness + complete relaxation of all muscles, patient may fall

4. Myoclonic Seizures: Shock like contraction of muscles of whole body momentary

5. Infantile Spasms [Hypsarhytmia] in infants; intermittent spasms + progressive mental deterioration

Partial siezures

1. Simple partial seizures: [sps] [cortical focal epilepsy]. ½ to 1 min; Often secondary; No unconsciousness; Convulsions confined to group of muscles or localised sensory disturbances. [parasthesia]

2. Complex partial Seizures: [cps] [temporal lobe epilepsy or psychomotor]. Bizarre confused behaviour & purposeless movements + impairment of consciousness + aura; focus often in temporal lobe

3. sps or cps; secondarily generalised: partial siezure slowly progresses to generalised tonic clonic siezures with loss of consciousness

Experimental models

1. Maximum electroshock siezure [MES] short electric shock to head of miceà tonic flexion -tonic extension - clonic convulsion [Abolished by Drugs effective in GTC]

2. Pentelene tetrazole injection in rats. Clonic convulsions: [abolished by drugs useful in absence seizures]

3. Chronic Focal siezures: Alumina to monkey’s motor cortex.

4. Repeated weak electric impulses to [amygdala] à tonic-clonic siezures [similar to clinical epilepsy]

Classification of Antiepileptic Drugs

1. Barbiturates: Phenobarbitone, Mephobarbitone

2. Deoxybarbiturates: Primidone

3. Hydantoins: Phenytoin

4. Iminostilbenes: Carbamazepine

5. Succinimides: Ethosuximide

6. Aliphatic carboxylic acid: Valproic acid

7. BZDs: Clonazepam, Diazepam, Clobazam

8. Newer Drugs: Lamotrigine, Gabapentin, Vigabatrin

9. Miscellaneous: Trimethadione, Acetazolamide

Category: Pharmacology Notes