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Epilepsy & Antiepileptic Drugs
This document discusses epilepsy and anti-epileptic drugs. It defines epilepsy as abnormal neuronal firing in the brain that causes seizures. Several causes of epilepsy are described, including birth trauma, infections, tumors, and head injuries. Seizures are classified as either generalized or partial/focal. Common generalized seizures include tonic-clonic, absence, myoclonic, and atonic seizures. Anti-epileptic drugs work by various mechanisms such as enhancing GABA activity, blocking sodium channels, or inhibiting glutamate receptors to decrease neuronal excitability and seizures. The major anti-epileptic drug classes are described along with their mechanisms of action.
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Epilepsy & Antiepileptic Drugs
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- 3. Contents • Epilepsy??? • Causes??? •Types Of seizures • Antiepileptic Drugs
- 4. INTRODUCTION • It isthe 3rd most common neurological disorder after cerebrovascular disease and Alzheimer's disease . • Epilepsy is not a single entity but the assortment of different seizure types and syndrome .
- 5. What is EPILEPSY? • It is the sudden , excessive and synchronous discharge of cerebral neurons . • This abnormal activity result in loss of conciousness , abnormal movement or odd behaviours .
- 6. EPILEPSYCONTD. • The symptomsthat are produced in epilepsy depends upon the site of origin of abnormal neuronal firing . • e.g if motor cortex is involved the patient may experience abnormal movement and generalized convulsion . if it originates from parietal and occipital lobe so visual , auditory or olfactory hallucinations occur .
- 8. WHATCAUSESEPILEPSY ? • INCHILDRENS : Birth traumas Infections Congenital abnormalities High fever • IN MIDDLE AGE : Head injuries Infection Alcohol Drug stimulant Medication side effects
- 9. INELDERLYAGE • Brain tumor Strokes OTHER: • It can also occur due to chemical imbalance includes drugs like alcohol, coccaine etc • Low blood sugar , low oxygen and low blood Na and Ca can also cause seizures .
- 10. ClassificationofEpilepticSeizures Generalized: 1.Generalized tonic-clonic seizure 2.Absenceseizure 3.Tonic seizures 4.Atonic Seizure 5.Myoclonic seizure • Partial (focal) Seizures: 80% of Adult epilepsies – Simple Partial Seizures – Complex Partial Seizures – Simple partial or complex partial secondarily generalized
- 11. Generalizedseizures 1. Generalized tonic-Generalizedtonic-clonic GTCS/major epilepsy/grand mal Commonest of all Lasts for 1-2 minutes Loss of consciousness followed by tonic phase and then clonic phase Usually occurs in both the hemispheres Seizures are followed by confusion and exhaustion due to depletion of glucose and energy stores . 2 phases: tonic phase followed by clonic phase Tonic phase: Sustained powerful muscle contraction (involving all body musculature) which arrests ventilation Clonic phase: Alternating contraction and relaxation, causing a jerking movement which could be bilaterally symmetrical
- 12. Absenceseizure: – Also calledminor epilepsy/petit mal – Generally occurs in 3 to 5 years of age last untill puberty . – Momentary loss of consciousness (not convulsion), patient stares at one direction – No convulsions , rapid eye blinking which last for 3-5 seconds . – No loss of postural control
- 13. AtonicSeizures : Unconsciousnesswith relaxation of all muscles Patient falls down Loss of postural tone, with sagging of the head or falling MyoclonicSeizures : Occur at any age but generally occur at puberty . Momentary contractions of muscles of limbs or whole body No loss of postural control Infantilespasm: An epileptic syndrome Characterized by brief recurrent myoclonic jerks (muscle spasm) of the body with sudden flexion or extension of the body and limbs Progressive mental deterioration
- 14. Partial(focal)Seizures • Simple partialseizure (Jacksonian) – Lasts for 20 – 60 seconds – Motor, sensory, or psychic symptomatology – Typically consciousness is preserved – Seizures are caused by group of hyperactive neuron exhibiting abnormal electrical activity and cofined to single locus .
- 15. • Complexpartialseizure(temporallobe/psychomotorepilepsy) • Focusis located in temporal lobe • Confused behavior and purposeless movements and emotional changes lasting for 30 seconds to 2 minutes • Motor dysfunction involve chewing movement , diarrhea and urination
- 18. Classificationon the basisofmechanismof action • DRUGSFACILATATINGGABAACTIONS: Barbiturates , benzodiazepine , gabapentin • INHIBITORSOF GABATRANSAMINASE: Facilitate GABA action: valproic acid , vigabatrin • DRUGSBLOCKINGNa CHANNELS: Decrease axonal conduction phenytion , carbamazepine ,valproic acid , primidone.
- 19. • Drug blockingT-type Ca Channels: Dec. presynaptic Ca influx Valproic acid • drudblocking “glutamate ” receptors: Dec. excitatory affects of glutamic acid. Topiramate
- 20. DrugblockingGlutamatereceptors • NMDA (N-myethyl-D-aspartate)receptor sites as targets – Ketamine, phencyclidine, dizocilpine block channel and have anticonvulsant properties but also dissociative and/or hallucinogenic properties; open channel blockers. – Felbamate antagonizes strychnine-insensitive glycine site on NMDA complex
- 21. GABAInhibitors • Benzodiazepines (diazapam,clonazapam) – Increase frequency of GABA-mediated chloride channel openings • Barbiturates (phenobarbital, primidone) – Prolong GABA-mediated chloride channel openings – Some blockade of voltage-dependent sodium channels
- 22. Gabapentin – May modulateamino acid transport into brain – May interfere with GABA re-uptake Tiagabine – Interferes with GABA re-uptake Vigabatrin – elevates GABA levels by irreversibly inhibiting its main catabolic enzyme, GABA-transaminase
- 23. Na+ChannelsBlockers Phenytoin,Carbamazepine – Block voltage-dependentsodium channels at high firing frequencies—use dependent Oxcarbazepine – Blocks voltage-dependent sodium channels at high firing frequencies – Also effects K+ channels Zonisamide – Blocks voltage-dependent sodium channels and T-type calcium channels
- 24. • Decrease Pre-synapticCalcium influx resulting in decrease transmitter release by neurons. • Ethosuximide: is a specific blocker of T-type currents and is highly effective in treating absence seizures BlockingT-TypeCa Channels
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