seizure disorders. 2 definition of seizures time-limited paroxysmal events that result from...
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Seizure Disorders
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Definition of seizures
Time-limited paroxysmal events that result from abnormal, involuntary, rhythmic neuronal discharges in the brain
Seizures are usually unpredictable
Seizures usually brief ( < 5 minutes) and stop spontaneously
Convulsion, ictus, event, spell, attack and fit are used to refer to seizures
Seizures that are prolonged or repetitive can be life-threatening
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Definition of epilepsy
Epilepsy is a disorder which is a symptom of disturbed electrical activity in the brain, which may be caused by a wide variety of etiologies
A collection of many different types of seizures that vary widely in severity, appearance, cause, consequence, and management
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Definition of epilepsy
Not uncommonly, patients have other comorbid disorders, including depression, anxiety, and potentially neuroendocrine disturbances.
Patients with epilepsy also may display neurodevelopmental delay, memory problems, and/or cognitive impairment
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Etiology of seizures Provoked Seizures: Triggered by certain provoking factors
in otherwise healthy brain
… Metabolic abnormalities (hypoglycemia and hyperglycemia, hyponatremia, hypocalcemia)
… Alcohol withdrawal
… Acute neurological insult (infection, stroke, trauma)
… Illicit drug intoxication and withdrawal
… Prescribed medications that lower seizure threshold (theophylline, TCA)
… High fever in children
Unprovoked Seizures: Occur in the setting of persistent brain pathology
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TABLE 62.1 Common Causes of New-Onset Seizures
Primary or Acquired Neurological Disorders Alzheimer's disease or other neurodegenerative diseases Brain tumor Central nervous system infection Cerebrovascular disease Febrile seizures of childhood Genetic or developmental disorders Head trauma Idiopathic/genetic Systemic or Metabolic Disorders Alcohol abuse and withdrawal Anoxia or ischemia Drug overdose or toxicity Eclampsia Hepatic failure Hypocalcemia Hypoglycemia Hypomagnesemia Hyponatremia Porphyria Renal failure
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Etiology of seizures Many medical conditions can cause
epilepsy.
A genetic predisposition to seizures has been observed in many forms of primary generalized epilepsy.
Patients with mental retardation, cerebral palsy, head injury, or strokes are at an increased risk for seizures and epilepsy
In elderly, seizures are primarily of partial onset associated with the focal neuronal injury induced by strokes, neurodegenerative disorders
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Etiology of seizuresfactors that precipitate seizures in
susceptible individuals.
Hyperventilation can precipitate absence seizures.
Sleep, sleep deprivation, sensory stimuli, and emotional stress increase the frequency of seizures.
Hormonal changes occurring around the time of menses, puberty, or pregnancy.
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Etiology of seizuresfactors that precipitate seizures in
susceptible individuals.
theophylline, alcohol, high-dose phenothiazines, antidepressants (especially maprotiline or bupropion), and street drug use have been associated with provoking seizures.
Perinatal injuries and small gestational weight at birth are risk factors for partial-onset seizures.
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Etiology of Epilepsy Any process that alters structure or function
of the brain neurons can cause epilepsy
Processes that lead to structural alteration include:
Congenital malformation
Degenerative disease
Infectious disease
Trauma
Tumors
Vascular process
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TABLE 62.2 Drugs That Have Been Associated With Provoking or Drugs That May Exacerbate Seizures
Antiarrhythmic agents (class 1B) Antimicrobials β-Lactams and related compounds Isoniazid Quinolones Antivirals Acyclovir Ganciclovir Drugs of abuse Amphetamine Cocaine Ephedra Methylphenidate Psychotropic agents Antidepressants Antipsychotics Lithium Sedative-hypnotic drug withdrawal Alcohol Barbiturates (short-acting) Benzodiazepines (short-acting) Miscellaneous Cyclosporine Lindane Flumazenil Metoclopramide Normeperdine (accumulation in renal failure) OKT3 Radiographic contrast agents Theophylline Tramadol
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Classification of seizures Traditionally divided into “ grand mal”
and “petit mal” seizures
ILAE classification of epileptic seizures in 1981 based on clinical observation and EEG findings
Seizures were divided into partial and generalized seizures based on loss of consciousness
Partial seizures were divided into simple partial and complex partial based on alteration of consciousness
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CLASSIFICATION OF SEIZURES
Seizures
Loss of Consciousness?
Yes No
Generalized Seizures Partial Seizures
Alteration of Consciousness?
Yes No
Complex Partial Simple Partial
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ILAE CLASSIFICATION OF SEIZURES
Partial Seizures Generalized Seizures
Complex Partial Seizures (CPS)–With automatism
–Without automatism
Simple Partial Seizures (SPS)–Motor
oWith marchoWithout marchoVersiveoPosturaloPhonatory
–SensoryoSomatosensoryoOlfactory oVisualoAuditoryoGustatoryoVertiginous
–Autonomic
–PsychiatricoDysphasicoDéjà vu or jamais vuoCognitiveoAffectiveoIllusionsoStructured hallucinations
Secondary Generalized Tonic-Clonic
Tonic-Clonic (primary tonic-clonic)
Absence
Myoclonic
Clonic
Tonic
Atonic
Atypical Absence
Infantile Spasm
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Clinical presentationSymptoms
CP seizures can include somatosensory or focal motor features.
CP seizures are associated with altered consciousness.
Absence seizures can be almost nondetectable with only very brief (seconds) periods of altered consciousness.
GTC seizures are major convulsive episodes and are always associated with a loss of consciousness.
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Clinical presentation Signs
… between seizure episodes there are typically no objective
Laboratory Tests
… There are currently no diagnostic laboratory tests for epilepsy.
… In some cases, GTC or CP), serum prolactin levels can be transiently elevated.
… Lab tests done to rule out treatable causes of seizures.
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Clinical PresentationOther Diagnostic Tests
EEG is very useful in the diagnosis
An epileptiform EEG is found in only approximately 50% of the patients who have epilepsy.
A prolactin level within 10 to 20 mins of a tonic-clonic seizure can be useful in differentiating seizure activity from pseudoseizure activity but not from syncope.
MRI is very useful (especially imaging of the temporal lobes)
CT scan typically is not helpful except in the initial evaluation for a brain tumor or cerebral bleeding.
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Generalized tonic-clonic seizures
begin with tonic (rigid) flexion of the extremities followed by extension.
The tonic phase usually lasts 15 to 20 seconds and is quickly followed by the clonic (jerking) phase, during which there are spasms of the trunk and extremities and often biting of the tongue.
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Generalized tonic-clonic seizures
The clonic phase usually lasts 20 to 30 seconds and is followed by a postictal state, during which the patient may sleep or awaken confused and disoriented.
gradual return of consciousness and orientation over a period of 15 to 30 minutes, after which the patient has no recall of the event.
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Generalized tonic-clonic seizures
Increases in blood pressure and heart rate, incontinence of urine or feces, and a brief interruption of normal breathing with cyanosis commonly accompany this type of seizure.
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Absence Seizures
Occur primarily during childhood
Characterized by an abrupt interruption of consciousness followed by a fixed stare.
Automatisms (coordinated involuntary movements such as lip smacking, chewing, or grimacing) or mild clonic movements may also occur.
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Absence Seizures there is no loss of postural tone.
lasts several seconds and ends as abruptly
may also cluster and occur as frequently as hundreds of times a day.
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Simple Partial Seizures Motor manifestations (e.g., clonic
jerking of one limb) or sensory symptoms (e.g., a foul odour or visual distortions).
Patients can respond to their environment throughout the attack.
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Complex partial seizures impaired consciousness and a
heterogeneous group of abnormal symptoms or behaviours.
Auras precede complex partial seizures in many patients.
Unusual epigastric sensations are the most common, although various motor, sensory, or psychic symptoms (as described for simple partial seizures) may occur.
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Complex Partial Seizures Consciousness is impaired for an
average of about 2 minutes.
During this time, patients may exhibit automatisms such as lip smacking, buttoning or unbuttoning of clothing, or wandering behaviour.
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TREATMENT
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Desired Outcome Accurately diagnose seizure type and
determine the etiology.
Identify and eliminate patient-specific seizure precipitants.
Select optimal AED based on seizure type, patient age, sex, and concomitant medical conditions.
Therapy should be individualized to attain best possible seizure control
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General approach to treatment
identification of goals
assessment of seizure type and frequency
development of a care plan
a plan for follow-up evaluation
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General approach to treatment Consider Patient characteristics such as age,
medical condition, ability to comply with a prescribed regimen
For new-onset seizures decide whether to use drug therapy or not.
If a decision is made to start AED therapy, monotherapy is preferred.
Patient education and assurance of patient understanding of the plan are essential.
… Detailed directions regarding titration, what to do in the event of a treatment-emergent side effect, and what to do if a seizure occurs
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Treatment of Seizures
Provoked Seizures
…Treatment directed to the provoking factor
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Treatment of Seizures Unprovoked Seizures
… First Seizure
Usually no treatment
Treatment initiated if risk of recurrence is high or if a 2nd seizure could be devastating
… Second Seizure
Diagnosis of epilepsy is established and risk of a third Seizure is high
In children, some may wait for a third seizure
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When to start AED initiate prophylactic treatment following a
CNS insult likely to cause epilepsy (e.g., stroke or head trauma).
AED may not be indicated in patients whose seizures have minimal impact on their lives.
a careful individual risk–benefit assessment.
treatment is recommended in all persons with a high risk of seizure recurrence
the side effects of AEDs need to be considered.
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When to start AEDHigh-risk features for seizure recurrence
symptomatic epilepsy with generalized tonic–clonic seizures
complex or simple partial seizures,
idiopathic generalized epilepsies.
Early treatment after a first GTCS has not been shown to improve long-term prognosis or lower mortality or the risk of injury
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When to start AED
Good prognoses who may not even require drug treatment
uncomplicated febrile seizures
benign idiopathic partial epilepsies
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Table 58-2 Recurrence Risk for Patients Experiencing One Unprovoked Seizure
Type of Patient First-Year Risk (%) Fifth-Year Risk (%)
Adults with single unproved seizure 34
No CNS insult 10 29
Influence of family history
Sibling with seizure 29 46
No sibling with seizures 7 27
EEG patterns GSW on EEG 15 58 Normal EEG 9 26
Occurrence of previous seizure 10 39
Caused by an illness or childhood febrile seizure
Remote symptomatic with Todd paresis 26 48
41 75
Status epilepticus at onset 37 56
Prior acute seizure 60 80 Idiopathic 10 29
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Nonpharmacologic therapy
Diet
Surgery
vagus nerve stimulation (VNS).
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Nonpharmacologic therapy Diet
… ketogenic diet devised in1920s.
… high in fat and low in CHO/ protein
… leads to acidosis and ketosis
… It requires strict control and parent compliance.
… poorly tolerated by patients.
… Long-term effects have included kidney stones, increased bone fractures, and adverse effects on growth.
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Nonpharmacologic therapy Surgery
… treatment of choice in selected patients with refractory focal epilepsy.
… success rate 80% and 90% in properly selected patients.
… surgery reduces the risk of epilepsy-associated death, and it may also improve depression and anxiety in refractory epilepsy patients.
… Learning and memory can be impaired postoperatively, and general intellectual abilities are also affected in a small number of patients.
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Nonpharmacologic therapy Surgery
A National Institutes of Health Consensus Conference identified three absolute requirements for surgery.
… an absolute diagnosis of epilepsy
… failure on an adequate trial of drug therapy
… definition of the electroclinical syndrome.
… Surgery may be particularly useful in children with intractable epilepsy. Patients may need to continue to receive AED therapy for a period of time
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Nonpharmacologic therapy vagus nerve stimulation (VNS).
… An implanted device approved as an adjunctive for partial-onset seizures refractory to AEDs.
… It is also used off-label in the treatment of generalized epilepsy.
… The mechanisms of antiseizure actions of VNS are unknown in the human.
… 23% to 50%of patients achieve > 50% reduction in their seizure frequency
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Nonpharmacologic therapy vagus nerve stimulation (VNS).
… The most common side effect are hoarseness, voice alteration, increased cough, pharyngitis, dyspnea, dyspepsia, and nausea.
… Serious adverse effects reported include infection, nerve paralysis, hypoesthesia, facial paresis, left vocal cord paralysis, left facial paralysis, left recurrent laryngeal nerve injury, urinary retention, and low-grade fever.
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FIGURE 58-1.
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Drug Therapy
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ANTIEPILEPTIC DRUGS (AED)
First Generation Second Generation
Unconventional
Carbamazepine (Tegretol)
Clonazepam (Klonopin)
Clorazepate (Tranxene)
Ethosuximide (Zarontin)
Phenobarbital
Phenytoin (Dilantin)
Primidone (Mysoline)
Valproic acid (Depakote)
Felbamate (Felbatol)
Gabapentin (Neurontin)
Lamotrigine (Lamictal)
Levetiracetam (Keppra)
Oxcarbazepine (Trileptal) Pregabalin (Lyrica)
Tiagabine (Gabitril)
Topiramate (Topamax)
Zonisamide (Zonegran)
Adrenocorticotropic hormone (ACTH )
Acetazolamide (Diamox)
Amantadine (Symmetrel)
Bromides
Clomiphene (Clomid)
Ethotoin (Peganone)
Mephenytoin (Mesantoin)
Mephobarbital (Mebaral)
Methsuximide (Celontin)
Trimethadione (Tridione)
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Choice of antiepileptic drug
the choice of first-line agents is based on
efficacy for the seizure or epilepsy syndrome,
Tolerability and safety,
ease of use,
pharmacokinetics (including current or likely future need for concomitant medication for comorbidity),
cost
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TABLE 62.6 Antiepileptic Drugs of Choice Based on Seizure Classification
Partial Seizuresa Generalized Seizures Generalized Tonic-Clonic Absence Myoclonic, Atonic, Atypical Absence
Drugs of choice Carbamazepine Phenytoin Lamotrigine Oxcarbazepine Topiramateb
Valproate Carbamazepine Phenytoin Topiramate Lamotrigine
Ethosuximide Lamotrigine Valproate
Valproate Lamotrigine
Alternatives Gabapentinb Levetiracetam Phenobarbital Pregabalin Primidone Tiagabineb Valproate
Levetiracetam Phenobarbital Phenytoin Primidone
Clonazepam Clonazepam Topiramate Felbamate
aSimple-partial, complex-partial, and secondarily generalized tonic-clonic seizures. bUsed primarily as adjunctive therapy.
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Seizure Type First-Line Drugs Alternative Drugsa CommentsPartial seizures (newly diagnosed) U.S. guidelines25,26
Adults & adolescents: FDA approved:
CarbamazepineCarbamazepine OxcarbazepineGabapentin PhenobarbitalLamotrigine PhenytoinOxcarbazepine TopiramatePhenobarbital Valproic acidPhenytoin Topiramate Valproic acid
U.K. guidelines27,28
Carbamazepine LamotrigineOxcarbazepineTopiramateValproic acid
ILAE guidelines29
Adults: Adults: Carbamazepine Gabapentin Phenytoin Lamotrigine Valproic acid Oxcarbazepine Phenobarbital Topiramate Children: Children: Oxcarbazepine Carbamazepine Phenobarbital Phenytoin Topiramate Valproic acid Elderly: Elderly: Gabapentin Carbamazepine Lamotrigine
U.S. Expert Panel 200530
Carbamazepine Levetiracetam Lamotrigine Oxcarbazepine
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Partial seizures (refractory monotherapy)
U.S. guidelines25,26
Lamotrigine FDA approved:
Oxcarbazepine Carbamazepine
Topiramate Lamotrigine
Oxcarbazepine
Phenobarbital
Phenytoin
Valproic acid
U.K. guidelines27,28
Lamotrigine
Oxcarbazepine
Topiramate
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Partial seizures (refractory adjunct) U.S. guidelines25,26
Adults: FDA approved:
Gabapentin Carbamazepine
Lamotrigine GabapentinLevetiracetam LamotrigineOxcarbazepine Levetiracetam
Tiagabine Oxcarbazepine
Topiramate PhenobarbitalZonisamide PhenytoinChildren: PregabalinGabapentin TiagabineLamotrigine Valproic acidOxcarbazepine Zonisamide
U.K. guidelines27,28
Gabapentin
Lamotrigine
Levetiracetam
Oxcarbazepine
Tiagabine
Topiramate
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Generalized seizures absence (newly diagnosed)
U.S. guidelines25,26
Lamotrigine FDA approved: Ethosuximide
Valproic acidU.K. guidelines27,28
Lamotrigine
ILAE guidelines29
None Ethosuximide Lamotrigine Valproic acid
U.S. Expert Panel 200530
Ethosuximide Lamotrigine Valproic acid
Primary generalized (tonic-clonic)
U.S. guidelines25,26
Topiramate FDA approved: Lamotrigine Topiramate
U.K. guidelines27,28
Lamotrigine Topiramate
ILAE guidelines29
None Adults: Carbamazepine Lamotrigine Oxcarbazepine Phenobarbital Phenytoin Topiramate Valproic acid Children: Carbamazepine Phenobarbital Phenytoin Topiramate Valproic acid
U.S. Expert Panel 200530
Valproic acid Lamotrigine Topiramate
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Juvenile myoclonic epilepsy
FDA approved:
Levetiracetam (myoclonic seizures)
ILAE29
None Clonazepam
Lamotrigine
Levetiracetam
Topiramate
Valproic acid
Zonisamide
U.S. Expert Panel 200530
Valproic acid Levetiracetam
Topiramate
Zonisamide
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PARTIAL SEIZURES partial seizures do not respond to
treatment as well as seizures that are generalized.
Carbamazepine, phenytoin, phenobarbital, and primidone are equally effective for the treatment of partial seizures
carbamazepine and phenytoin are usually tolerated better.
Phenytoin has a long half-life that allows for once-daily dosing
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PARTIAL SEIZURES
phenytoin is associated with cosmetic
changes that make it less desirable for the
treatment of epilepsy in children,
adolescents, and women.
Valproate is also useful for the treatment of
partial seizures, but carbamazepine
provides better seizure control and fewer
long-term adverse effects.
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PARTIAL SEIZURES
Felbamate, gabapentin, lamotrigine,
tiagabine, topiramate, levetiracetam,
oxcarbazepine, zonisamide, and pregabalin
are also effective for treating partial seizures.
Lamotrigine and topiramate are effective as
monotherapy and appear to be better
tolerated than carbamazepine monotherapy
particularly in elderly patients.
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PARTIAL SEIZURES
Phenobarbital and primidone are also useful in partial seizures, but sedation and cognitive adverse effects limit their utility.
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PARTIAL SEIZURES The first AED leads to complete seizure
control in about 50-65%% of patients
Subsequent combination or substitution achieve control in up to 10–15%.
1 in 3 patients remains with uncontrolled partial seizures.
The other new agents are primarily used as adjunctive therapy if monotherapy has failed or for patients who are intolerant of standard AEDs (e.g., carbamazepine, phenytoin, and valproate).
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PARTIAL SEIZURES If several single-drug or combination
regimens with these drugs have failed, surgical options should be considered.
If not, third-line agents are available; these are clobazam, phenobarbital, phenytoin, primidone, and tiagabine.
Less often used agents with either tolerability or safety problems or no Class I evidence for efficacy (acetazolamide, bromide, felbamate, sulthiame, vigabatrin) should be used as a last resort.
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GENERALIZED SEIZURES Valproate, lamotrigine, and topiramate are
the drugs of choice for the treatment of primary generalized tonic-clonic seizures.
insufficient data to support the use of any of the new AEDs as monotherapy in newly diagnosed primary generalized tonic-clonic seizures
topiramate was recently approved as initial monotherapy for primary generalized seizures in those older than 10 years of age.
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GENERALIZED SEIZURES 75% to 85% of patients achieve complete
seizure control during monotherapy with VPA
Lamotrigine and topiramate are emerging as more often used therapies in children younger than 2 years of age because of the higher risk of valproate-associated hepatotoxicity in this population.
Phenobarbital and primidone are also effective, but because of their potential for adverse effects, they are usually reserved for second-line or third-line agents.
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GENERALIZED SEIZURES Carbamazepine, phenytoin, and
oxcarbazepine can rarely exacerbate seizures in patients with primary generalized epilepsy syndromes.
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Absence seizures Ethosuximide, VPA and lamotrigine are
effective for the treatment of absence seizures.
Ethosuximide may be preferred over VPA when only absence seizures are involved because of the potential for fewer serious adverse effects.
Ethosuximide is not effective against GTC seizures; therefore, valproate and lamotrigine are preferred if this seizure type is also present.
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Absence seizures 70% to 90% of patients who were treated
with ethosuximide or valproate experienced cessation or a dramatic reduction in absence seizures.
The combination of ethosuximide and valproate is often effective when monotherapy fails to yield adequate results
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Absence seizures Clonazepam is also effective against
absence seizures.
it should be reserved for patients in whom ethosuximide and valproate fail because of frequent dose-related adverse effects and the development of tolerance
Carbamazepine , phenobarbital, and phenytoin are ineffective for the treatment of absence seizures and may even exacerbate it
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Myoclonic, atonic, and atypical absence seizures VPA is effective for the treatment of
myoclonic, atonic, and atypical absence seizures and is the initial drug of choice for patients with mixed seizure types.
It controls myoclonic seizures in 75% to 90% of patients with generalized idiopathic and juvenile myoclonic epilepsy.
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Myoclonic, atonic, and atypical absence seizures Clonazepam is also effective as
monotherapy or in combination with VPA when either drug alone does not provide adequate seizure control.
Lamotrigine, topiramate, zonisamide, and felbamate are also effective against myoclonic, atonic, and atypical absence seizures.
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Advantages of modern AEDs less enzyme inducing than CBZ, PHT or r
barbiturates
less enzyme inhibiting than VPA, or do not influence hepatic enzyme systems at all.
causes fewer adverse drug interactions.
fewer hormona metabolic disturbances
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Advantages of modern AEDs malformation rate associated with LTG is
similar to CBZ or untreated women with epilepsy and is lower than VPA.
the absence of hypersensitivity reactions.
a modern AED should be preferred over a classic AED when starting drug treatment in a patient with new-onset epilepsy.
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Finding the optimal dose of AED The drug is titrated to the lowest effective
dose.
If seizures continue, the daily dose is increased by small increments to the average effective dose
Most AEDs work within several days to a week of starting treatment.
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Finding the optimal dose of AED If seizure control cannot be achieved with
the maximum tolerated dose, a dose reduction
to the previous average dose is recommended. If toxic symptoms or high plasma concentrations indicate an increased risk of toxicity before seizures are controlled, a second AED is added.
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Monitoring treatment with antiepileptic drugs Target plasma AED concentrations are
available for a number of drugs.
Plasma concentrations are less useful than the clinical course.
Some patients have toxic symptoms at low concentrations, whereas others tolerate higher concentrations without apparent clinical symptoms.
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Monitoring treatment with antiepileptic drugs If treatment is ineffective, monitoring of
concentration may unmask irregular drug compliance
Except for PHT, for which monitoring is strongly recommended because of the nonlinear saturation dose kinetics, monitoring of other AED plasma concentrations is optional and should be individualized (e.g., poor drug compliance or adverse events).
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Monitoring treatment with antiepileptic drugs The therapeutic range for AEDs can be
different for different seizure types.
… higher to control CP seizures than to control tonic-clonic seizures.
Patients should be monitored chronically for seizure control, comorbid conditions, social adjustment (including quality-of-life assessments), drug interactions, compliance, and adverse effects.
.
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Monitoring treatment with antiepileptic drugs Periodic screening for comorbid
neuropsychiatric disorders such as depression and anxiety is also important
Clinical monitoring involves identifying the number and type of seizures.
…a seizure diary.
…
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ADVERSE EFFECTS Acute effects
… dose/serum concentration–related or idiosyncratic.
… Neurotoxic adverse effects
sedation, dizziness, blurred or double vision, difficulty with concentration, and ataxia.
can be alleviated by decreasing drug dose or avoided in some cases by increasing the drug very slowly.
… Most idiosyncratic reactions are mild, but they can be more serious including hepatitis or blood dyscrasias are serious but rare.
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ADVERSE EFFECTS Acute effects
… Acute organ failure, generally occurs within the first 6 months.
… laboratory evaluations are not helpful in predicting or detecting the early stages and not recommended in asymptomatic patients.
… WBC and LFTs if the patient reports an unexplained illness (e.g., lethargy, vomiting, fever, or rash).
… adverse effects can occur despite serum concentrations within therapeutic range
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ADVERSE EFFECTS Chronic effects
… osteomalacia and osteoporosis.
… ranging from asymptomatic high-turnover disease, with normal BMD, to markedly decreased bone BMD (osteoporosis)
… Etiology uncertain
… hypothesized that phenytoin, phenobarbital, carbamazepine, oxcarbazepine, and valproic acid, may interfere with vitamin D metabolism.
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ADVERSE EFFECTSChronic effects
osteomalacia and osteoporosis.
… ranging from asymptomatic high-turnover disease, with normal BMD, to markedly decreased bone BMD (osteoporosis)
… Etiology uncertain
… hypothesized that phenytoin, phenobarbital, carbamazepine, oxcarbazepine, and valproic acid, may interfere with vitamin D metabolism.
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ADVERSE EFFECTSChronic effects
cognition impairment
… No large differences between the older drugs
… phenobarbital and primidone appear to cause more cognitive impairment
… Phenytoin, particularly when serum concentrations are above the commonly accepted therapeutic range
… valproic acid may cause less impairment of cognition.
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ADVERSE EFFECTSChronic effects
cognition impairment
… Patients changed from polytherapy to monotherapy also may demonstrate improvement
… newer agents believed to cause fewer neurobehavioral or cognitive effects.
… gabapentin and lamotrigine have been shown cause fewer cognitive impairments as compared with older agents
… topiramate may cause substantial cognitive impairment, when used at high doses or during rapid dose escalation.
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ADVERSE EFFECTSChronic effects
worsening of seizures
… can result from either improper selection of an AED for a specific seizure type
… can represent a paradoxical toxic effect of the drug
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Antiepileptic drug interactions
Older AEDs such as phenytoin, carbamazepine, phenobarbital and valproic acid can significantly interfere not only with each other and other AEDs, but also with other treatments.
Although newer AEDs have a more favourable pharmacokinetic profile, they are not entirely exempt from interactions andthey are also commonly administered in combination with older AEDs.
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Antiepileptic drug interactions
The AEDs that most commonly cause interactions with each other and with other drugs are older AEDs:
phenytoin, carbamazepine, phenobarbital, primidone and valproic acid.
Pharmacokinetic characteristics: they have high protein-binding capacity, exclusively or predominantly hepatic metabolism, potent enzyme induction and inhibition, and active intermediate metabolites.
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Antiepileptic drug interactions
In certain groups of patients, failure to anticipate potential interactions of AEDs with each other and with other drugs could lead to a major management problem
Patients with refractory epilepsy and elderly people are sections of the population in whom polypharmacy is the norm.
The interaction of AEDs with contraceptives is an aspect that must be taken into consideration in young women.
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Antiepileptic drug interactions
Cancer patients, patients undergoing treatment with immunosuppressants and those who are HIV positive or have a psychiatric disorder, often take drugs that interact with AEDs.
Antiepileptics are becoming increasingly widely used in other common conditions such as neuropathic pain and migraine.
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Therapeutic considerations in the elderly and young Avoidance of AEDs that interact with other
medications that the elderly are taking.
… Many of the drugs are inducers or inhibitors of the CYP450 system,
Hypoalbuminemia is common in elderly, which can make monitoring and adjustment of serum drug levels of highly albumin-bound AEDs, such as phenytoin, valproic acid, and tiagabine, problematic.
increase in fat to lean body mass or decrease in body water, can affect the volume of distribution of some drugs, and therefore possibly the elimination half-life
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Therapeutic considerations in the elderly and young declining renal and/or hepatic function require a
lower dose of the AED.
the pharmacodynamic response to AEDs can change as the patient ages because elderly patients may be more sensitive to various neurocognitive adverse effects of these drugs.
Elderly patients may demonstrate efficacy (e.g., control of seizures) at relatively lower serum concentrations as well.
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Therapeutic considerations in the elderly and young For neonates and infants, an increase in the total
body water to body fat ratio and a decrease in serum albumin and -acid glycoprotein can result in volume of distribution changes that can affect the elimination half-life of the AEDs.
newborns up to the age of 2 to 3 years display decreased efficiency in renal elimination, with the newborn having the most significant impairment.
Hepatic activity is also reduced in this population.
by age 2 to 3 years, hepatic activity is more robust than in adults. Therefore, children require higher doses than adults, whereas neonates and infants require lower doses.
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THERAPEUTIC CONSIDERATIONS IN WOMEN Estrogen has a seizure-activating effect
progesterone exerts a seizure-protective effect.
Hepatic enzyme inducers, increase the metabolism of steroid hormones and induce the production of sex hormone–binding globulin.
…decreases in the unbound fraction of the hormone.
… topiramate and oxcarbazepine at higher doses, can cause treatment failures in women taking oral contraceptives.
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THERAPEUTIC CONSIDERATIONS IN WOMEN
…Valproic acid, benzodiazepines, and most of the newer AEDs, such as gabapentin, levetiracetam, tiagabine, and zonisamide, are not enzyme inducers and have not been associated with this effect.
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THERAPEUTIC CONSIDERATIONS IN WOMEN In some women, vulnerability to seizures
is highest just before and during the menstrual flow and time of ovulation.
This can be related to progesterone withdrawal and changes in the estrogen-to-progesterone ratio.
Conventional AEDs should be tried first in these women.
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THERAPEUTIC CONSIDERATIONS IN WOMEN Intermittent acetazolamide also
has been used but with variable and limited success.
Hormonal therapy with progestational agents also can be effective.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY the possibility of increased maternal
seizures, pregnancy complications, and adverse fetal outcome.
Approximately 25% to 30% ↓and ↑
Increased seizure activity may result from either a direct effect on seizure threshold or a reduction in AED concentration.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY An increase in clearance has been
reported for phenytoin, carbamazepine, phenobarbital, ethosuximide, lamotrigine, oxcarbazepine, and clorazepate.
Protein binding also may be altered.
… as early as the first 10 weeks of pregnancy and can take up to 4 weeks postpartum to return to normal.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY There is a higher incidence of adverse
pregnancy outcomes in women with epilepsy(4% to 6%)
barbiturates and phenytoin are associated with congenital heart malformations, orofacial clefts, and other malformations.
Valproic acid and carbamazepine are associated with spina bifida (neural tube defect) and hypospadias.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY the risk of neural tube defect
appears to be related to drug exposure during gestational days 0 to 28.
Other adverse outcomes associated with maternal seizures, but not necessarily caused by AEDs, are growth, psychomotor, and mental retardation.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY Women with epilepsy are also more
likely to have miscarriages
Many of these teratogenic effects can be prevented by adequate folate intake;
Higher folate doses should be used in women with a history of a previous pregnancy with a neural tube defect.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY New AEDs are reported to be less
teratogenic,
clinical data are still limited, and more experience is needed.
Some AEDs also can lead to neonatal hemorrhagic disorder, which can be prevented by the administration of vitamin K 10 mg orally, given to the mother daily during the last month of pregnancy.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY Although AEDs pass into the breast
milk, the concentrations are very low, and the infant receives a subtherapeutic dose.
Taking AEDs with less protein binding results in more accumulation in breast milk.
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THERAPEUTIC CONSIDERATIONS IN PREGNANCY The perimenopausal period can be
associated with worsening of seizures, possibly owing to fluctuations in sex hormones.
At menopause, seizures actually can improve
The effect of hormone-replacement therapy on seizure control is still unclear.
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CLINICAL CONSIDERATIONS WITH SPECIFIC DRUGS
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CARBAMAZEPINE
Advantages
Oral immediate- and extended-release solid and liquid dosage forms are available
The sustained- and controlled-release dosage forms allow for twice-daily dosing to reduce the peak-to-trough fluctuations.
Compared with other first-generation AEDs, carbamazepine causes minimal cognitive impairment.
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CARBAMAZEPINE has an active metabolite that can
contribute to efficacy and toxicity.
Other drugs can alter the concentration of this metabolite without changing the concentration of the parent carbamazepine.
It induces its own metabolism, which requires careful dosage titration.
It also induces the metabolism of other medications, and other drugs may interact with it and/or the active metabolite
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CARBAMAZEPINE
no parenteral formulation.
clinically meaningful CNS side effects including sedation and nausea.
Chronic carbamazepine use also has been associated with alterations in bone mineral density in some studies and decreases in 25-hydoxy (OH) vitamin D.
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CARBAMAZEPINE
Place in Therapy
first-line therapy for patients with newly diagnosed partial seizures and for patients with primary generalized convulsive seizures who are not in an emergent situation
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GABAPENTIN
Advantages
has multiple mechanisms of action and is mechanistically different from first-generation AEDs.
It is not metabolized and is excreted unchanged by the kidney.
Has a broad therapeutic index with minimal CNS adverse effects and no drug interactions.
Doses can be escalated rapidly.
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GABAPENTIN
Disadvantages
absorbed by an active process that saturates at higher doses.
This may require more frequent daily dosing for patients who need doses greater than 3,600 mg/day.
Doses >3,600 mg/day may be required in some patients to achieve seizure remission.
There is no parenteral formulation.
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GABAPENTIN
Place in Therapy
second-line agent for patients with partial seizures who have failed initial treatment
may be a role in patients with less severe seizure disorders, such as new-onset partial epilepsy, particularly in the elderly patient.
has been shown to be useful in the treatment of chronic pain and other nonepileptic conditions.
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LEVETIRACETAM
Advantages
not metabolized by the cytochrome P450 system and no significant drug interactions,
Well tolerated, with transient sedation
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LEVETIRACETAM
Disadvantages
Dose adjustments are needed for patients with decreased renal function
Slower dose escalation may be needed to avoid CNS adverse effects.
Behavioral problems can limit therapy in some patients.
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LEVETIRACETAM
Place in Therapy
indicated for patients with partial seizures who have failed initial therapy.
recently approved as adjunctive treatment for myoclonic seizures in patients with juvenile myoclonic epilepsy.
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PHENYTOIN
Advantages
Phenytoin has been used for more than 65 years
It is available in multiple dosage forms, allowing flexibility in dosing and use in emergent situations.
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PHENYTOIN
Disadvantages
metabolism saturates at doses given clinically. This makes phenytoin a challenging drug to dose.
Phenytoin is an inducer of cytochrome P450 isozymes, is metabolized by cytochrome P450 enzymes, and is highly protein bound.
Phenytoin is associated with multiple significant adverse effects.
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PHENYTOIN
Place in Therapy
a first-line AED for primary generalized convulsive and partial seizures.
Its use in therapy may be reevaluated as more experience is gained with newer AEDs.
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TOPIRAMATE
Advantages
Topiramate has multiple mechanisms of action and is a broad-spectrum AED.
The kidney mainly eliminates it, although some liver metabolism occurs, especially if given concomitantly with enzyme inducers.
It has liner pharmacokinetics and few drug interactions.
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TOPIRAMATE
Disadvantages
With rapid dosage escalation, topiramate can compromise cognitive functioning, including impaired word finding and short-term memory.
Renal stones and weight loss also have been associated with topiramate use.
There is no parenteral formulation.
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TOPIRAMATE
Place in Therapy
Topiramate is a first-line AED for patients with partial seizures.
The drug is also approved for the treatment of tonic-clonic seizures in primary generalized epilepsy.
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VALPROIC ACID/DIVALPROEX SODIUMAdvantages
available in multiple dosage formulations. The IV formulation is especially well tolerated.
It has a wide therapeutic index and can be considered a broad-spectrum AED.
It can be useful in other neurologic or psychiatric disorders, including migraine headache and bipolar disorder.
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VALPROIC ACID/DIVALPROEX SODIUMDisadvantages
Some patients report significant weight gain which s can limit compliance.
Associated with alopecia, tremor, pancreatitis, polycystic ovary disease, and thrombocytopenia.
It has been associated with hepatic necrosis in young children.
It is an enzyme inhibitor and is involved in multiple drug-drug interactions
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VALPROIC ACID/DIVALPROEX SODIUMPlace in Therapy
Valproic acid is first-line therapy for primary generalized seizures such as myoclonic, atonic, and absence seizures.
It can be used as both monotherapy and adjunctive therapy for partial seizures
it can be very useful in patients with mixed seizure disorders.