7 - Antiseizure Drugs Flashcards by Nupur Reddy

An event due to abnormally discharging cerebral neurons

Seizure

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Recurrent seizures

Epilepsy

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Abnormal electrical activity is limited to part of the brain/one cerebral hemisphere

Partial seizure

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Seizure with no alteration of consciousness (consciousness is preserved)

Simple partial seizure

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Seizure with altered consciousness, automatisms, & behavioral changes (consciousness is lost)

Complex partial seizure

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Abnormal activity is occurs in the entire brain/both cerebral hemispheres

Generalized seizure

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Seizure with increased muscle tone followed by spasms of muscle contraction & relaxation

Tonic-clonic seizure

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Seizure with increased muscle tone

Tonic seizure

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Seizure with rhythmic, jerking spasms

Myoclonic seizure

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Seizure with sudden loss of all muscle tone

Atonic seizure

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Seizure with brief loss of consciousness, with minor muscle twitches and eye blinking

Absence seizure

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Which synapses have molecular targets for antiseizure drugs?

Excitatory glutamatergic & Inhibitory GABAergic synapses

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Pathophysiology of Seizures at excitatory glutamateric synapse?

Increased excitatory amino acid (EAA) - glutamate
Increased Glu & Asp at start of seizure
Up-regulation of NMDA receptors
Increased EAA transmission & sensitivity to EAA

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Pathophysiology of Seizures at inhibitory GABAergic synapse?

Decreased GABA
Decreased Cl- currents in response to GABA
Decreased binding of GABA and benzodiazepines
Decreased glutamate decarboxylase activity (synthesizes GABA)
Interfere with GABA causes seizures

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What drugs stabilize Na+ channels?

(VLTPC: V Like To Proper Channel)

Valproic acid, Lamotrigine, Topiramate, Phenytoin, Carbamazepine

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What drugs stabilize Ca2+ channels?

Ethosuximide, Valproic acid

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What drugs enhance GABA transmission?

(BBVGVTF: BaBy V Gaba Vay Too Far)
Benzodiazepines (diazepam, clonazepam), Barbiturates (phenobarbital), Valproic acid, Gabapentin, Vigabatrin, Topiramate, Felbamate

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What drugs inhibit EAA transmission?

Felbamate, Topiramate

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What kind of seizures is Clonazepam used for?

Absence seizures

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When a seizure lasts longer than 5 minutes or when seizures occur close together and the person doesn’t recover between seizures

Status Epilepticus

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What are the different types of status epilepticus?

Convulsive & Non-convulsive

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Which type of status epilepticus requires emergency treatment?

Convulsive status epilepticus

What is Phenytoin’s MOA?

Inhibits Na+ channels of axons, decreasing influx of Na, also blocks Ca2+ channels at high doses

Absorption of Phenytoin?

Oral absorption is less, poorly soluble in water, has high plasma protein binding

Metabolism of Phenytoin?

First pass metabolism, follows zero order kinetics, metabolism occurs in liver by hydroxylation

_______ exhibits genetic polymorphism. Responsible for variation in plasma concentration of drug by a given dose

Phenytoin

What is the therapeutic plasma concentration of Phenytoin?

10-12 micrograms/mL

Indications for Phenytoin?

1) Partial seizures: simple & complex 2) Generalized seizures: Tonic-clonic (Grandmal) and Status epilepticus 3) Arrhythmias (Digoxin toxicity) 4) Bipolar disorders

Adverse effects of Phenytoin?

Nystagmus & Ataxia, Fetal hydantoin syndrome (cleft lip & cleft palate), Megaloblastic anemia

What kind of drug is Fosphenytoin?

Prodrug, rapidly converts to phenytoin in body after I.V. or I.M. administration

What are the pros of Fosphenytoin?

Avoids complications that come with Phenytoin (vein irritation, tissue damage, muscle necrosis, burning at site, need for lots of fluids)

Are the toxicities of Fosphenytoin similar to Phenytoin?

Yes

Indications of Fosphenytoin?

Admin. during Status Epilepticus

What is the MOA of Carbamazepine?

Blocks Na+ channels of axons -> decreases A.P. frequency

What are the indications for Carbamazepine?

Partial – simple & complex Generalized - Tonic-clonic (grand mal seizures) Trigeminal neuralgia Bipolar disorder -> up regulate adenosine receptor -> block NE re-uptake

What are Carbamazepine drug interactions?

Induces P450 | Cimetidine & Isoniazid increase Carbamazepine

What are the contraindications for Carbamazepine?

Pregnancy

What are the adverse effects of Carbamazepine?

``` Vertigo, Nystagmus, Ataxia, Diplopia Sedation & Respiratory depression Aplastic anemia - Granulocytopenia Megaloblastic anemia, Thrombocytopenia Hepatotoxic Teratogenic – Coarse facial features & Spina bifida. Exfoliate dermatitis ```

MOA of Oxcarbazepine?

Blocks voltage-sensitive Na+ channels and may augment K+ channels

What kind of drug is oxcarbazepine?

Considered a prodrug, its activity is attributed to monohydroxy metabolite

What is the clinical use for Oxcarbazepine?

approved for monotherapy, or add-on therapy in partial seizures

What are the adverse effects of Oxcarbazepine?

Some induction of P450 but much less than that seen with Carbamazapine Sedating but otherwise less toxic than Carbamazapine

What is the MOA for Eslicarbazepine?

Blocks Na+ channels of axons -> decreases A.P. frequency

How often is Eslicarbazepine administered?

Once a day

What is the MOA of Valproic Acid?

Blocks presynaptic Ca2+ influx in thalamus, blocks axonal Na+ channels, inhibits GABA transaminase -> increase of GABA, decrease Glutamate synthesis

Indications of Valproic Acid?

- Seizures: Generalized - Myoclonic, Atonic, Absence, Tonic-clonic - Migraine - Bipolar disorder

Adverse effects of Valproic Acid?

``` Ataxia, Tremor Hepatotoxicity Pancreatitis Alopecia Photosensitivity Teratogenic (spina bifida) Thrombocytopenia Inhibits platelets aggregation ```

Contraindications for Valproic Acid?

Pregnancy

Drug interactions with Valproic Acid?

Inhibits P450 enzymes

What is the MOA of Lamotrigine?

Blocks voltage-sensitive Na+ channels

What is the Clinical Use of Lamotrigine?

Partial seizures in adults and children. Adjuvant therapy Generalized tonic-clonic, atonic, absence seizures. Adjuvant therapy Lenox-Gastaut syndrome (LGS) – monotherapy a syndrome characterized by multiple types of seizures in patients with mental retardation and other neurologic abnormalities. Manic phase of bipolar disorder

Metabolism of ________ is affected by Valproate, Carbamazapine, Phenobarbital, & Phenytoin

Lamotrigine

Adverse Effects of Lamotrigine?

Less sedating than other AEDs Severe dermatitis in 1-2% of pediatric patients Cerebellar dysfunction, drowsiness, and rash, Stevens-Johnson syndrome. Aseptic meningitis