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ANTISEIZURE DRUGS. Zenaida N. Maglaya,MD,FPSECP Department of Pharmacology. SEIZURE. Is a finite episodes of brain dysfunction resulting from abnormal discharge of cerebral neurons. PRIMARY SEIZURES SECONDARY SEIZURES. CLASSIFICATION OF SEIZURE TYPES. PARTIAL SEIZURES

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ANTISEIZURE DRUGS

Zenaida N. Maglaya,MD,FPSECP

Department of Pharmacology


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SEIZURE

  • Is a finite episodes of brain dysfunction resulting from abnormal discharge of cerebral neurons.

  • PRIMARY SEIZURES

  • SECONDARY SEIZURES


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CLASSIFICATION OF SEIZURE TYPES

PARTIAL SEIZURES

  • Simple partial seizures

  • Complex partial seizures

  • Partial seizures secondarily generalized


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CLASSIFICATION OF SEIZURE TYPES

GENERALIZED SEIZURES

  • Generalized tonic-clonic (grand mal) Sz

  • Absence (petit mal) seizures

  • Tonic/ Atonic Seizures

  • Clonic & myoclonic seizures

  • Infantile Spasms

  • Febrile Seizures

  • Status Epilepticus


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PRIMARY DRUGS

  • CARBAMAZEPINE

  • PHENYTOIN

  • VALPROIC ACID

  • PHENOBARBITAL

  • PRIMIDONE

  • DIAZEPAM /LORAZEPAM

  • CLONAZEPAM

  • ETHOSUXIMIDE


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ADJUNCTIVE DRUGS

FELBAMATE GABAPENTIN

LAMOTRIGINE TIAGABINE

TOPIRAMATE VIGABATRIN

LEVETIRACETAM ZONISAMIDE


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ANTISEIZURES CLASSIFICATION

I. TONIC-CLONIC & PARTIAL SEIZURES

  • Carbamazepine. Phenytoin, valproic acid

    II.ABSENCE SEIZURES

  • Ethosuximide, valproic acid, clonazepam

    III MYOCLONIC SEIZURES

  • Valproic acid, clonazepam

    IV. ADJUNCT/NEWER ANTICONVULSANTS


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MECHANISM OF ACTION

  • Inhibition of sodium channels function: phenytoin, carbamazepine, lamotrigine

  • Inhibition of calcium channel function:ethosuximde

  • Enhancement of GABA action: benzodiazepines,phenobarbital gabapentin,vigabatrin, tiagabine

  • Multiple & Complex Mechanism: Valproic Acid


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PHENYTOIN

  • BLOCK SODIUM CHANNELS

  • USE: partial seizures; generalized tonic-clonic seizures, Antiarrhymic drug0

  • Oral, IV

  • highly bound to plasma proteins

  • T ½ 12 -36 hrs

  • Metabolized, dose dependent elimination

  • Fosphophytoin, mephenytoin, ethotoin.

  • phenacemide


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Phenytoin Adverse Effects

  • nystagmus, diplopia, ataxia, sedation, gingival hyperplasia & hirsutism, coarsening of facial features, mild peripheral neuropathy, megaloblastic anemia fever, skin rash, fetal hydantoin syndrome


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PHENYTOIN DRUG INTERACTIONS

  • Sulfonamides, valproate & phenylbutazone: displace phenytoin from binding sites

  • Cimetidine, disulfiram, doxycycline, isoniazid, phenylbutazone, sulfas, warfarin, chloramphenicol: inhibits phenytoin metabolism


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PHENYTOIN DRUG INTERACTIONS

3.Barbiturates & carbamazepine, pyridoxine, theophylline: enhance phenytoin metabolism

4.PHENYTOIN decreasesserum levels of: carbamazepine, chloramphenicol, corticosteroids, haloperidol, quinidine, theophylline, oral contraceptives, warfarin


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CARBAMAZEPINE

  • BLOCK SODIUM CHANNELS

  • DOC for partial seizures

  • Generalized tonic-clonic seizures

  • Trigeminal neuralgia

  • Mania:bipolar disorders

  • Orally absorbed with slow distribution

  • Completely metabolized

  • CAUSE: diplopia & ataxia, idiosyncratic blood dyscrasias, aplastic anemia & agranulocytosis, leukopenia


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CARBAMAZEPINE DRUG INTERACTIONS

1. Increase carbamazepine levels via metabolism: cimetidine, erythromycin, isoniazid

2. Decrease carbamazepine levels via increase metabolism: phenytoin, valproic acid

3. Carbamazepine decreases drug levels :warfarin, oral contraceptives, doxycycline, phenytoin, haloperidol

4. Carbamazepine increases drug levels : cimetidine, isoniazid

5. Lithium induces carbamazepine toxicity.


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PHENOBARBITAL

  • Enhancement of inhibitory process

  • Dimimution of excitatory transmission

  • USE: partial seizures, generalized tonic-clonic seizures

  • May cause: CNS depression

  • Tolerance & dependence

    CI in porphyria disorders


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PHENOBARBITAL DRUG INTERACTIONS

  • Increase phenobarbital levels via metabolism; acute ethanol ingestion, chloramphenicol, valproic acid

  • Decrease phenobarbital levels via increase metabolism, chronic alcohol ingestion, pyridoxine, rifampin

  • Barbiturates decrease serum levels: tricyclics, warfarin, beta blockers, oral contraceptives, digitoxin, doxycycline, metronidazole, theophyllline


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PRIMIDONE

  • Metabolized to:

  • PHENOBARBITAL

  • PHENYLETHYLMALONAMIDE(PEMA)

  • Mechanism of action similar to phenytoin

  • May cause sedation, ataxia, vertigo, GIT upset, megaloblastic anemia

  • CI: porphyria, hypersensitivity


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VIGABATRIN

  • Inhibits GABA transaminase

  • Partial seizures & ‘WEST syndrome

  • In patients unresponsive to conventional drugs

  • Rapid absorption

  • T ½ 6 -8 hrs

  • CAUSES: drowsiness, behavioral & mood changes, weight gain, visual field defect


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LAMOTRIGINE

  • Inhibits sodium channels

  • Partial seizures

  • Absense seizures

  • Completely absorbed

  • T ½ of 24 hours

  • Broad therapeutic profile

  • CAUSES: hypersensitivity rxns, diplopia, ataxia, headache, dizziness, life threatening skin disorders, hematotoxicity


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FELBAMATE

  • MOA is unknown

  • For partial seizures

  • Broad therapeutic profile

  • For intractable cases

  • T ½ is 20 hrs

  • CAUSES: severe hypersensitivity rxs aplastic anemia, hepatotoxicity

  • Increase plasma phenytoin & valproic acid

  • Decrease carbamazepine levels


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GABAPENTIN

  • MOA: alters GABA metabolism, its nonsynaptic release or its reuptake by GABA transporters

  • Also binds to the α2δ subunit of voltage sensitive calcium channels

  • FOR PARTIAL & GENERALIZED SEIZURES

  • SATURABLE ABSORPTION

    CAUSE: somnolence, dizziness, ataxia, headache & tremor


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TOPIRAMATE

  • Complex action: GABA effect, blocks voltage dependent sodium channels

  • Similar to phenytoin with lower side effects & simpler pharmacokinetics

  • Risk of teratogenesis

  • Sedation, mental dulling, renal stones, weight loss


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TIAGABINE

  • Nicotinic acid derivative

  • GABA uptake inhibitor in both neurons & glia

  • Partial seizures

  • Dizziness, tremor, difficulty in concentration, psychosis


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ETHOSUXIMIDE

  • DOC for absense seizures

  • Effect on calcium channels( reduce low threshold (T type) currents

  • Inhibits NA/K/ ATPase, depresses the cerebral metabolic rate & inhibits GABA aminotransferase

  • Absorption is complete

  • Completely metabolized

  • CAUSES; gastric distress, lethargy & headache

  • DI: valproic acid inhibits its metabolixm


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VALPROIC ACID

  • On partial seizures sodium channel effects

  • Increased levels of GABA inhibits GABA transaminase & succinic semialdehyde dehydrogenase

  • Sodium channel blockade


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VALPROIC ACID

  • CLINICAL USES:

    1. ABSENCE SEIZURES

    2. MYOCLONIC SEIZURES

    3. GENERALIZED TONIC-CLONIC TYPE OF SEIZURES

    4. ATONIC ATTACKS

    5. PARTIAL SEIZURES

    6. MIGRAINE PROPHYLAXIS

    7. BIPOLAR DISORDER


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VALPROIC ACID

  • Well absorbed; ppc within 2 hrs

  • Bioavailability > 80%

  • T ½ is 9 -18 hrs

  • CAUSES: nausea, vomiting, pain & heart burn, sedation uncommon, fine tremors, weight gain, increase in appetite & hair loss, hepatotoxicity, thrombocytopenia,

  • SPINA BIFIDA


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VALPROIC DRUG INTERACTIONS

  • Decrease valproic acid levels from increase metabolism with carbamazepine

  • Increase valproic acid levels with antacid (increase absorption)

  • salicylates (displacements from binding sites)

  • When used with clonazepam may precipitate absence status


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BENZODIAZEPINES

  • Diazepam, lorazepam, clonazepam, clorazepate, Nitrazepam, clobazam

  • Well absorbed, widely distributed

  • Extensively metabolized with many active metabolites

  • May cause sedation, tolerance

  • DIAZEPAM: DOC for status epilepticus


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STATUS EPILPETICUS

  • DIAZEPAM

  • LORAZEPAM

  • PHENYTOIN

  • PHENOBARBITAL



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Thank You!!!

And we know that all things work together for good to those who love God, to those who who are called according to His purpose.

ROMANS 8: 28