Anticonvulsants are drugs used to treat seizures and epilepsy. They are classified into different groups including barbiturates, hydantoins, oxazolidinediones, succinimides, ureas, benzodiazepines, and miscellaneous drugs. Phenytoin is a commonly used anticonvulsant that works by blocking sodium channels. It is used to treat generalized tonic-clonic seizures, partial seizures, and status epilepticus. Common side effects include gingival hyperplasia and drug interactions. Other anticonvulsants discussed include carbamazepine, ethosuximide, trimethadione, clonazepam, and sodium valproate

1. anticonvulsants
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2. Anticonvulsants are the drugs used in the treatment of experimentally
produced seizures in laboratory animals and antiepileptic are drugs used
medically to control the epilepsies not all of which are convulsive in
humans.
Epilepsy is a disease due to central nervous system disorder which is
characterized by seizures and convulsion or other abnormal body
movements with loss of disorder of consciousness.
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3. classification
Barbiturates:- eg: phenobarbitone, mephobarbitone
Hydantoins:- eg: phenytoin, mephenytoin, ethotoin
Oxazolidinediones:- eg: trimethadione, paramethadione
Succinimides:- eg: phensuximide, methsuximide, ethosuximide
Urea and monoacyl ureas:- eg: carbamazepine
Benzodiazepines:- eg: clonazepam, diazepam, chlorazepate
Miscellaneous:- eg: primidone, valproic acid, zonisamide, gabapentin, tiagabine,
felbamate, phenacemide
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4. barbiturates
Most of the barbiturates are sedative and hypnotics, only few of them
show anticonvulsant characters.
General structure
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Name R1 R2 R3
Phenobarbitone C2H5 C6H5 H
Mephobarbitone C2H5 C6H5 CH3
Metharbital CH3 CH3 CH3

5. S A R
Optimum activity is obtained when one substituent at C5 is phenyl.
The 5,5- diphenyl derivative has less activity than phenobarbitone.
N1 and N3 substitution in some case also resulted in increased activity.
5,5- dibenzyl barbituric acid causes convulsion.
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6. hydantoins
The hydantoins are close structural relatives of barbituric acid, differing in
lacking of 6-oxo groups.
The lack of this carbonyl gp decreases the acidity, so it is weaker acid than
that of barbiturates.
2,4 - imidazolidinedione
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7. Generic name Substituents
R1 R2 R3
PHENYTOIN C6H5 C6H5 H
MEPHENYTOIN C6H5 C2H5 CH3
ETHOTOIN C6H5 H C2H5
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8. S A R
5 phenyl or other aromatic substituents is essential for activity.
Alkyl group in the 5th position contributes sedation, a property which is
absent in phenytoin
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9. 1) PHENYTOIN
Synthesis
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10. Mechanism of action
It is a sodium channel blocker.
Both the Na+ and Cl- ions are invariably present at much higher
concentration outside the cell, whereas K+ charged proteins and organic
cations are more abundantly available inside the cell.
Epileptic seizures causes Na+ ion accumulation within the central neuron,
which initiates enhanced synaptic nerve transmissions following presynaptic
stimulation.
Phenytoin decreases Na+ intracellular ion by activating biochemical process
that normally extrudes Na+ ion from neurons.
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11. USES
Phenytoin is used in the treatment of;
1. Generalized tonic-clonic seizures.
2. Partial seizures.
3. Trigeminal and other neuralgias.
4. Status epilepticus ; phenytoin is administered intravenously in
normal saline.
DOSE
100-200 mg twice daily oral, 25 mg/min slow i.v injection.
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12. ADVERSE EFFECTS
1. Hypertrophy and Hyperplasia of gums.
2. Hypersensitivity reactions include skin rashes,neutropaenia
3. Megaloblastic anaemia
4. Osteomalacia
5. It can inhibit insulin release and cause hyperglycaemia.
6. Foetal hydantoin syndrome- cleft lip,cleft palate etc.. due to use of
phenytoin during pregnancy
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13. DRUG INTERACTIONS
1. Carbamazepine and phenytoin induce each other’s metabolism.
2. Valproate displaces protein bound phenytoin and decreases its
metabolism; plasma level of unbound phenytoin increases.
3. Chloramphenicol, isoniazid, cimetidine and warfarin inhibit
phenytoin metabolism- can precipitate toxicity
4. Phenytoin competitively inhibits warfarin metabolism
5. Phenytoin induces microsomal enzymes and increases degradation
of steroids, doxycycline,theophylline.
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14. 2) FOSPHENYTOIN
Fosphenytoin is a water -soluble phenytoin prodrug that is administered
intravenously to deliver phenytoin, potentially more safely than
intravenous phenytoin.
USE:- It is most commonly used in the acute treatment convulsive status
epilepticus.
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15. OXAZOLIDINEDIONES
Replacement of the NH group at position 1 of the hydantoin systems with
oxygen atoms yields the oxazolidine-2,4-dione system.
3) TRIMETHADIONE
USE:- It is used in the treatment of petit mal epilepsy. Dermatological and
hematological toxicities limit its clinical use. 15
3,5,5-trimethyl
oxazolidin-2,4-dione

16. SUCCINIMIDES
4) ETHOSUXIMIDE[zarontin]
USE:- It is effective in the cure of petit mal epilepsy
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3- Ethyl-3-methyl
pyrrolidin-2,5-dione

17. Urea and monoacyl urea
5) CARBAMAZEPINE[Tegretol]
USE:- It is used to control grand mal and focal seizures. It is used in the
treatment of trigeminal neuralgia and treatment of manic depression.
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5H –Dibenz-[b,f]-azepin-
5-carboxamide

18. BENZODIAZEPINES
6) CLONAZEPAM
USE:- It is effective in all type of epilepsy i.e. grand mal, psychomotor,
petit mal, myoclonic and status epilepsy.
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19. MISCELLANEOUS
7) SODIUM VALPROATE
VALPROIC ACID
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20. Sodium valproate is moderately effective against chemically & electrically
induced seizures in animals & possesses a satisfactory margin of safety.
Mechanism of action:-
◦ Its mechanism of action may be related to increased brain levels of the
inhibitory neurotransmitter, gamma amino butyric acid (GABA).
◦ This increase in brain content of GABA is due to the inhibition of enzyme that
metabolize GABA by sodium valproate.
Use:- It is a drug of choice in patients with typical absence seizures. It is
also useful in the treatment of grandmal seizures.
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21. synthesis
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