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Anti-epileptic drugs

This document provides information on anti-epileptic drugs (AEDs) including their mechanisms of action, uses, and side effects. It discusses the classification, treatment, and management of epilepsy and seizures. Some key points include: - AEDs work by enhancing GABA inhibition, blocking sodium channels, or inhibiting calcium currents to suppress neuronal firing and seizures. - Common AEDs include phenytoin, carbamazepine, valproic acid, lamotrigine, levetiracetam, and topiramate. - AEDs are used to treat generalized tonic-clonic, absence, myoclonic and partial seizures. Some are also used for neuropathic

Health & Medicine◦
ANTI-EPILEPTICS Dr Mangala MBBS, MD
EPILEPSY : Group of disorders of CNS characterized by recurrent seizures, with or without characteristic body movements(convulsions) often accompanied by episodes of unconsciousness and / or amnesia.
SEIZURES : Transient alteration in behavior because of disordered firing of groups of neurons in the brain. Causes : Idiopathic Trauma during child birth Head injury Febrile seizures Brain tumors Meningitis
TYPES OF SEIZURES :  Partial seizures: Unilateral localized origin in the brain. (cortical/temporal lobe) • Simple partial • Complex partial • Partial with secondarily generalized seizures  Generalized seizures : Diffuse origin involving both the hemispheres of the brain. • Absence seizures • Myoclonic seizures • Atonic seizures • Tonic- clonic seizures
 GENERALIZED TONIC CLONIC SEIZURES : • Also called Grand mal , GTCS, major epilepsy. • Usual sequence aura – cry – unconsciousness and patient falls. • Tonic spasm of all the body muscles, clonic jerking followed by prolonged sleep and depression of all CNS functions.
 ABSENCE SEIZURES: • Petitmal , minor epilepsy. • No or only momentary loss of consciousness, no fall, patient apparently freezes and stares in one direction, no muscular component or minimal bilateral jerking or blinking of eyes. • Multiple episodes may occur each day. • Remit spontaneously in adolescence.  ATONIC SEIZURES: • Akinetic epilepsy. • Brief loss of consciousness with relaxation of all muscles due to excessive discharges. • Patient may fall.
 MYOCLONIC SEIZURES: • Shock like momentary contraction of muscles of a limb or the whole body. • Myoclonic jerking may accompany any type of generalized or partial seizures.
PARTIAL SEIZURES :  SIMPLE PARTIAL SEIZURES: • Sudden onset • Unilateral clonic jerking of a group of muscles or a limb lasting 30 -90 sec, or localized sensory distrubances such as pin pricks, visual auditory hallucinations, etc. depending on the area of the cortex involved. • Patient remains conscious and aware of the attack.
 COMPLEX PARTIAL SEIZURES: • Attacks are bizarre and confused behaviour, dream like state and purposeless movements, or even walking unaware, emotional changes lasting 1- 2 mins along with impairment of consciousness. • Patient cannot recollect the attack. • An aura often precedes. • Seizure focus – temporal lobe – Temporal lobe epilepsy.
 SIMPLE PARTIAL OR COMPLEX PARTIAL SEIZURES SECONDARILY GENERALIZED : • Partial seizures occurs first and evolves into generalized tonic clonic seizures with loss of consciousness.
CLASSIFICATION : Hydantoins : Phenytoin Fosphenytoin Barbiturates : Phenobarbitone Deoxybarbiturate : Primidone GABA transaminase inhibitors : Valproic acid(sodium valproate) Divalproex Iminostilbene : Carbamazepine oxcarbazepine Succinimide : Ethosuximide
 Benzodiazepines :  Diazepam  Clonazepam  Lorazepam  Clobazam NEWER AGENTS :  GABA analogs :  Gabapentin  Pregabalin  Others :  Lamotrigine  Levetiracetam  Lacosamide  Felbamate  Topiramate  Zonisamide  Vigabatrin  Tiagabine
Clinical Classification
MECHANISM OF ACTION OF ANTI EPILEPTICS :  Blockade of Sodium channel or prolongation of their inactive state delaying the recovery. E.g. : Phenytoin, Carbamazepine, Lamotrigine
 Blockade of low threshold Calcium current in the thalamic neurons – controls absence seizures. E.g. : Ethosuximide.
Enhancing GABA mediated inhibition :  Acting on GABA receptors : Benzodiazepines, barbiturates  Inhibiting GABA metabolism : Valproic acid, vigabatrin Blocking excitatory glutamate receptors : Topiramate
Benzodiazapines
PHENYTOIN • PHARMACOKINETICS : Absorption is slow . Should not be given I.M. Fosphenytoin can be given I.M. 90% bound to plasma proteins. Metabolized by liver initially by first order kinetics later Zero order kinetics at high doses. • MECHANISM OF ACTION: • Prolongs inactivation of sodium channels • Stabilises neuronal membrane • Inhibition of excitatory glutamanergic synapse.
• USES: • Generalised tonic clonic seizures • Partial seizures • Trigeminal neuralgia • Status epilepticus • Digitalis induced cardiac arrhythmia
PHENYTOIN INTERACTIONS: • Phenytoin induces microsomal enzymes & enhances the breakdown of OC pills, Vit D and steroids thereby reducing the effectiveness of co- administered drugs. • Phenytoin – carbamazepine : mutual induction of metabolism and reduced plasma conc. of both drugs . • Chloramphenicol, INH, warfarin – Phenytoin: these drug inhibit metabolism of phenytoin  increase in plasma conc. of phenytoin  phenytoin toxicity.
PHENYTOIN • ADVERSE EFFECTS: • Gum hypertrophy • Hirsutism • Acne • Hypersensitivity reactions • Hyperglycaemia • Megaloblastic anaemia
• Fetal Hydantoin syndrome: cleft lip, cleft palate, microcephaly • Due to phenytoin therapy during pregnancy – teratogenic effect
FOSPHENYTOIN • Prodrug. Advantages over phenytoin: • More potent • Less cardiotoxic • Can injected into glucose/normal saline drip • Can be given I.M. and I.V
PHENOBARBITONE MECHANISM OF ACTION : • Enhancing the activation of GABA A receptors Facilitating the GABA mediated opening of chloride ion channels. • It is also an enzyme inducer. USES : • Generalized tonic clonic seizures. • Partial seizures
CARBAMAZEPINE • MECHANISM OF ACTION : • Prolongs inactivation of voltage gated sodium channels • Stabilises neuronal membrane • USES: • GTCS • Partial seizures • Trigeminal neuralgia • Acute mania & bipolar disorder
CARBAMAZEPINE Drug interactions: • Phenytoin, Phenobarbitone, sodium valproate, OC pills – Carbamazepine induces the metabolism & reduces the effects of these drugs. • INH, Erythromycin – inhibit carbamazepine metabolism leading to its toxicity.
CARBAMAZEPINE • ADVERSE EFFECTS : • GIT: Nausea, vomiting • CNS: Sedation, drowsiness, vertigo, ataxia, diplopia, confusion • Hypersensitivity reactions: skin rashes • Bone marrow depression: Neutropenia, Agranulocytosis, Aplastic anaemia
OXCARBAZEPINE : Similar to carbamazepine. Lesser side effects.
ETHOSUXIMIDE • PHARMACOKINETICS : Absorption – oral route, metabolized by liver. • MECHANISM OF ACTION : • Inhibits T-type of Calcium currents in thalamic neurons. • USES : • Drug of choice for Absence seizures • ADVERSE EFFECTS : • GIT: Nausea, vomiting • Hypersensitivity reactions • Bone marrow depression
SODIUM VALPROATE • MECHANISM OF ACTION: • Prolongs inactivation of voltage gated Na+ channels • Inhibits T-type of Ca2+ currents in thalamic neurons • Increases the synthesis of GABA by increased activity of GABA synthase. • Decreases the metabolism of GABA transaminase enzyme.
SODIUM VALPROATE • USES: • Absence seizures • GTCS • Partial seizures • Mania and bipolar disorder • Prophylaxis of migraine.
SODIUM VALPROATE • ADVERSE EFFECTS : • GIT: Nausea, vomiting • CNS: sedation, ataxia, tremors • Hypersensitivity reactions • Alopecia • Pancreatitis • Fulminant hepatitis • Neural tube defects • Polycystic ovarian disease (PCOD) in young girls.
SODIUM VALPROATE • Sodium Valproate- Phenytoin: Phenytoin toxicity due to displacement interaction. • Valproate inhibits the degradation of phenobarbitone & increases its conc. • Valproate – Carbamazepine: when administered simultaneously increased incidence of teratogenicity.
GABAPENTIN MECHANISM OF ACTION : • Increases the activity of GABA in brain by • Increasing its synthesis • Decreasing its metabolism
• USES: • Simple & partial complex seizures • Post herpetic neuralgia • Bipolar disorder • Diabetic neuropathy • Prophylaxis of migraine • ADVERSE EFFECTS : Headache, sedation, ataxia, fatigue
LAMOTRIGINE • MECHANISM OF ACTION : • Prolongs inactivation of voltage gated sodium channels • USES: • GTCS • Simple & complex partial seizures • Absence seizures • Myoclonic seizures • ADVERSE EFFECTS: Nausea, vomiting, headache, ataxia, sedation, skin rashes
• LEVETIRACETAM : • Acts on synaptic vesicle glycoprotein 2A (SV2A) • Effective against partial and secondarily generalized seizures. • Add on drug in refractory partial seizures. • TOPIRAMATE : • Monosaccharide • Blocks the sodium channels, enhance GABA A receptor currents. • Partial and generalized seizures.
OTHER CLINICAL USES • Several antiseizure drugs are effective in the management of bipolar affective disorders • Valproic acid used as a first-line drug • Carbamazepine and lamotrigine also used • Carbamazepine and oxcarbazepine are the drug of choice for trigeminal neuralgia
OTHER CLINICAL USES….. • Gabapentin and Pregabalin in neuropathic pain (e.g postherpetic neuralgia) • Migraine Prophylaxis: Phenytoin, Topiramate
• Children born of mothers taking anticonvulsant drugs have an increased risk of congenital malformations • Valproic acid cause Neural tube defects (eg, spina bifida) • Carbamazepine cause craniofacial anomalies and spina bifida • Phenytoin cause fetal hydantoin syndrome TERATOGENICITY
OVERDOSAGE TOXICITY • CNS depressants, and respiratory depression may occur with overdosage • Flumazenil may be used in benzodiazepine overdose
LIFE-THREATENING TOXICITY • Fatal hepatotoxicity has occurred with valproic acid (children younger than 2 yr has high risk) • Lamotrigine has caused skin rashes and life-threatening Stevens-Johnson syndrome or toxic epidermal necrolysis • Zonisamide may also cause severe skin reactions
WITHDRAWAL • Abrupt withdrawal may increased seizure frequency and severity • Withdrawal should be gradual
STATUS EPILEPTICUS • Characterised by recurrent attacks of seizures without the recovery of consciousness in between or single episode lasts for more than 30min. • It is a medical emergency
TREATMENT: • Hospitalize the patient. • Maintain airway and establish a I.V line • Administer oxygen • Collect blood for estimation of glucose, calcium, electrolytes and urea. • Maintain fluid and electrolytes.
TREATMENT OF STATUS EPILEPTICUS• Step 1: • Lorazepam 0.1mg/kg slow I.V. or • Diazepam 5 - 10mg I.V. every 10-15minutes upto 30mg slowly • Step 2: • Fosphenytoin 20mg/kg i.v. infusion. or • Phenytoin 20mg/kg I.V. Infusion • Step 3: • Phenobarbitone 10-15mg/kg i.v.infusion • Step 4: • General anaesthesia with Midazolam or Propofol I.V.
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