Antiepileptics

DEFINITION
 Epilepsy
 Epilepsy is a chronic disorder of brain
function characterized by recurrent
seizures often accompanied by episodes
of unconsciousness or amnesia.
 Seizure
 Seizure is a transient alteration in
behaviour because of disordered firing
of group of neurons.

CLASSIFICATION OF
ANTIEPILEPTICS
 HYDANTOINS-Phenytoin, Mephenytoin
 BARBITURATES- Phenobarbotone,
Mephobarbitone
 DEOXYBARBITURATES - Primidone
 IMINOSTILBENE - Carbamazepine
 SUCCINIMIDE - Ethosuximide
 GABA transaminase inhibitor - Valproic acid
 BENZODIAZEPINES - Diazepam,Clonazepam,
Lorazepam

CLASSIFICATION (Cont...)
 NEWER AGENTS
 GABA analogs - Gabapentin ,vigabatrin
 OTHERS - Zonisamate,felbamate

PHENYTOIN
 PHARMACOLOGICAL ACTION
 CNS - Phenytoin has good anti seizures
activity and is one of the most effective
drugs against generalized tonic-clonic
seizures and partial seizures.

Phenytoin
Blocks Na + Channels in Post
Synaptic Neuron
Inhibits the action Potential of
Neurons

ADVERSE EFFECTS
 Nausea, vomitting, epigastric pain
 Hypersensitivity
 Megaloblastic anemia
 Teratogenicity –when taken to the
pregnant lady ,it produce fetal
hydantoin syndrome (Cleft Palate, Cleft
lip & Microcephaly)
 Hyperglycemia

USES
 1. Generalized tonic clonic seizures and
partial seizures
 2.Status epileptics –phenytoin is used by
slow IV Injection.
 3.trigeminal neuralgia – as an
alternative to carbamazepine.
 4.cardiac arrhythmias- phenytoin is
useful in digitalis induced arrhythmias.

Drug interaction
 Phenytoin is an enzyme inducer.
phenobarbitone competitively inhibit s
phenytoin metabolism.
 Carbamazepine and pheytoin enhances
each others metabolism.
 Valproate displace protein bound and
may result in phenytoin toxicity.
 Antacid ↓ absorption of phenytoin.

Fosphenytoin
 It is a prodrug of phenytoin that has
certain advantages over phenytoin for
Parenterally use:
 It is quickly converted to phenytoin in
the body.
 More potent.
 Less cardiotoxic.
 Safer on the intestine.

PHENOBARBITONE
 It has specific antiepileptic activity.
Primidone which is rarely used .
Phenobarbitone is effective in tonic-
clonic seizures and ineffective in absence
of seizures.

MECHANISM OF ACTION
 Acts on the Synapse
 Enhance the action of Inhibitory neurotransmitters
(Eg. GABA)
 Suppresses the excitatory neurotransmitters (Ach)
 Opens Cl – ion Channels
 Decreases the Seizures

Pharmacokinetics
 Oral Absorption
 50 % bounds to plasma
proteins
 Metabolizes in liver
 Excreted via urine

ADVERSE EFFECT
 Sedation
 Megaloblastic anemia
 Osteomalacia
 Ataxia
 Skin rashes
 USES
 Generalized tonic –clonic seizures
 Partial seizures

CARBAMAZEPINE
 Carbamazepine is a tricyclic compound
 Anti seizure activity
It has good Anti seizure activity .its
mechanism of action and anti epileptic
action are similar to phenytoin.
 Carbamazepine is also used in the
treatment of trigeminal neuralgia

ADVERSE EFFECTS
 Drowsiness
 Vertigo
 Nausea & Vomiting
 Ataxia
 USES
 Generalized Tonic – Clonic Seizures
 Simple & Complex, Partial Seizures
 Trigeminal Neurolgia

VALPORIC ACID MoA
 Enhances the level of GABA (↓se
Metabolism of GABA)
 Blocks Na + Channels
 Decreases low threshold Ca + current in
thalamus
 Reduce Seizure

ADVERSE EFFECTS
 Sedation, Rashes, Ataxia and Tremors
USES
 Partial & Generalized Seizures
 Useful particularly in Absence Seizures (Petit
Mal Seizures)
 Generalized Tonic Clonic Attacks

BENZODIAZEPINE
 Diazepam is the drug of choice in status
epilepticus.
 Clonazepam is a potent anti epileptic drug
useful in absence and myoclonic seizures.
 Nitrazepam is used for treatment of
myoclonic seizures.

NEWER ANTI
EPILEPTICS
 Gabapentin – It is a highly lipid soluble
drug.
 It crosses the BBB.
 Effective in tonic clonic seizure
 Exact MoA is unknown.

CHOICE OF ANTI SEIZURE
DRUGS Simple / Partial Seizure – Carbamazepine,
Phenytoin, Valproic Acid
 Complex / Partial Seizure - Carbamazepine,
Phenytoin, Valproic Acid
 Partial with Secondarily Generalized -
Carbamazepine, Phenytoin, Valproic Acid
 Absence Seizures – Valproic Acid
 Tonic Clonic Seizure - Carbamazepine, Phenytoin,
Valproic Acid
 Tonic Clonic + Absence Seizure – Valproic Acid
 Myoclonic Seizures – Diazepam, Valproic Acid
 Status Epilepticus – Diazepam, Phenytoin, GA
 Febrile Convulsion - Diazepam

Antiepileptics

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Antiepileptics