Epilepsies are a group of disorders of the CNS characterized by paroxysmal cerebral dysrhythmia seizures and convulsions . This ppt includes types of seizures according to lippincott , classification of antiepileptic drugs according to KD tripathi book . Mechanism of action of classified drugs , choice of drugs and thier adverse effects + side effects . This ppt aims to give summary of antiepileptic drugs .

1. Antiepileptic drugs Mpharm 1st yr Pharmacology advanced pharmacology
ANTIEPILEPTIC DRUGS
Drugs acting on central nervous
system
GCU, GUWAHATI
PRESENTED BY-PRACHI MEHTA
MPHARM-1ST yr 2023-24

2. contents
Epilepsies are a group of disorders of the CNS characterized by paroxysmal cerebral dysrhythmia,
seizures and convulsions.
Keywords
1.Epilepsy
2.Types of seizures
3.Classification of drugs
4.MOA of classified drugs
5.Choice of drug
6.Adverse effect and side effect
Lesson over view
Seizure, convulsion , EEG , clonic ,tonic

3. 5
min
1. Introduction
Epilepsy also known as a seizure disorder , is a brain condition having recurrent episodes of
seizures. A seizure is a sudden , uncontrolled burst of electrical activity in the brain . It can
cause changes in behavior , movements , feelings and level of consciousness.
1.Seizures generally occur due to imbalance of neurotransmitter .
2.Excitatory neurotransmitter = inhibitory neurotransmitter -> No seizures.
3.Excitatory neurotransmitter increased > inhibitory neurotransmitter decreased leads to
seizures .
4. Excitatory neurotransmitter = glutamate
5. Inhibitory neurotransmitter = GABA , Gamma amino butyric acid.

4. Types of seizures
• A .FOCAL – involves only a portion of one hemisphere of the brain. Focal seizure might
progress to become bilateral.
• B. GENERALISED-: may begin locally, progress to begin abnormal electrical discharge through
out both hemispheres of brain. They are of diff. types -:
• 1. TONIC – CLONIC= loss of consciousness , rapid tonic clonic phase , confusion, exhaustion,
fall , spasm due to depletion of glucose and energy.(1-2min)
• 2. ABSENCE= in kids, stand and stare, no fall , EEG – 3 cycle per sec. (1/2min)
• 3. MYOCLONIC= Short episodes of muscle contraction and limb jerks after waking.
• 4. CLONIC = same as myoclonic , but consciousness is more impaired.
• 5. TONIC = Increased tone in extension muscles and generally less than 60s .
• 6. ATONIC= known as drop attacks , characterised by sudden loss of muscle tone . Patient
falls.

5. CLASSIFICATION OF ANTIEPILEPTIC DRUGS
Prolongation of Na+ channel
inhibition
Phenytoin, carbamazepine, valproate
Lamotrigine, topiramate
Facilitation of Gaba mediated cl-
channel opening
Barbiturate, benzodiazepine, vigabatrin,
valproate
Inhibition of excitatory glutamatergic
synapse
Phenytoin , valproate , phenobarbitone
Inhibition of T type Ca2+ current
Ethosuximide , Valproate, zonisamide
Antiepileptic
drugs

6. Prolongation of Na+ channel inhibition
• During normal conditions – opening of Na+ channel caused generation of action
potential. Then channels closed leading to inactivation . This inactivation makes them
refactory to a stimulus .
• During seizures – neuron depolarises which opens Na+ channel , and in response it
fires action potential at high frequency leading to seizures.
• Rest[1mili sec] Na+ active[1mili sec] inactive [1mili sec]
1.

7. MOA of drugs of this class
• 1. anticonvulsant drugs bind to Na+ channel in inactivated but still open state.
• 2. Prolongation of inactive state [ can be upto 100 mili seconds ] .
• 3. Na+ channel is not able to come in resting state , this inactivation makes them
refactory to a stimulus and further activation is not possible.
• 4. thus the rate of recovery of Na+ channel is reduced and there is limitation in the
neuronal activities , to fire at high frequency and thereby seizures are controlled.
• Drugs = phenytoin, carbamazepine, valproate , lamotrigine , topiramate, zonisamide
1.

8. Facilitation of GABA Transmission
GABA is synthesised from glutamate by GAD [glutamic acid decarboxylase] . GABA is
removed by neuronal uptake . When there is decrease in Gaba neurotransmitter ,
seizures occur. In treatment Gaba neurotransmitter is increased while glutamate
neurotransmitter is decreased.
Gaba receptor has 5 subunits of 2 alpha , 2 beta and 1 gamma . During seizures gaba is
reduced , which decreases the flow of chloride ions into the cell . This action
depolarises the neuron and cause excitation , leading to seizures .
MOA – 1. Gaba binds with beta subunit .
2. chlorine channel opens
3. hyperpolarisation of neurons
4. inhibition of seizures.
Drugs- barbiturate, benzodiazepine, valproate, vigabatrin
2.

9. MOA of drugs of this class
1. barbiturate binds to an accessory site on Gaba[either on alpha or beta subunit]
2. increase affinity of GABA receptor to GABA increasing life time of cl- channel opening
caused by GABA .
3. Hyperpolarisation of neurons .
4. inhibition of seizures.
• Barbiturates act either as facilitatory by increasing affinity of Gaba or as mimetic by
opening cl- channel .
• Valproate and vigabatrin inhibit enzyme Gaba transaminase which degrade Gaba,
thereby increasing its concentration .
2.

10. Inhibition of excitatory glutamatergic synapse
In normal condition , glutamate and aspartate , major excitatory neurotransmitter of
brain , acts on NMDA or AMPA receptor [ N-methyl –D-Aspartate].
This leads to more excitation and causes seizures.
MOA – antiepileptic drug [ felbamate] acts by inactivating NMDA receptor. And this
leads to control of seizures.
Drugs – phenytoin , phenobarbitone , valproate
3.

11. Inhibition of t type ca2+ current .
Transient current is low threshold ca2+ channel due to inward flow of Ca2+ through T
type calcium channel.
This leads to more excitation and causes absence seizures.
MOA – inhibits T type calcium channel .
Drugs – Ethosuximide, zonisamide , valproate
4.

12. MOA of antiepileptic diagram with diagram

13. CHOICE OF DRUG

14. 5
min
ADVERSE EFFECT
• P p-450 interaction
• H Hirsutism
• E enlarged gums
• N nystagmus
• Y yellow browning of skin
• T teratogenicity
• O Osteomalasia
• I interference with b12 metabolism
• N neuropathies = vertigo , ataxia , headache
• Phenytoin should not be taken by pregnant lady , carbamazepine can be taken for all but
not for absence seizures .
• Other side effects include – CNS depression , hallucination . Nausea , blurring of vision ,
dullness , arrhythmia etc.

15. 5
min
REFERENCE
1.KD Tripathi(2019) , Essentials pf medical pharmacology , Antiepileptic drugs , chapter 30 ,
page 438 – 450. Jaypee Brothers medical publisher .
2.Jeannie M Conway and Angela k Birnbaum Lippincott illustrated reviews pharmacology,
Drugs for epilepsy chapter12 , page 239 Wolters Kluwer(India) publication

16. THANK YOU