Download - Group 1 - Anticonvulsants
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ANTICONVULSANTS
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Anticonvulsants
Drugs used for epileptic seizures Suppress the abnormal electric impulses
from the seizure focus to other cortical areas Prevents the seizure but not eliminating the cause
of the seizure Classified as Central Nervous System depressant Usually taken throughout persons lifetime but
may be discontinued if there has not been aseizure for the past 3-5 years
Also known as anti-epileptic
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Two most common seizures
1. Tonic-Clonic Seizure also called grand
mal seizure; most common form of
seizures. In the tonic phase, the skeletalmuscles contract or tighten in a spasm,
lasting3 to 5 seconds. In the clonic phase,
there is a dysrhythmic muscularcontraction, or jerkiness, of the legs and
arms, lasting 2 to 4 minutes.
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2. Absence seizure also called petit
mal seizure; brief loss of
consciousness lasting less than 10seconds; fewer than three spike
waves on the electroencephalogram
(EEG) printout, usually occurs inchildren.
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Action of Anticonvulsants
By suppressing sodium influx through the drug bindingto the sodium channel when it is inactivated, thus
prolonging the channel inactivation and thereby neuron
firing By suppressing the calcium influx, thus preventing the
electric current generated by the calcium ions to the T-calcium channel
By increasing the action of gammaaminobutyric acid(GABA), which inhibits neurotransmitter throughout thebrain
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Types of Anticonvulsant
1. Hydantoins
First anticonvulsant used to treat seizures
Discovered in 1938 and is still the mostcommonly used drug for controlling seizures
Has the least toxic effects, has a small effect on
general sedation, an is nonaddictingShould not be used during pregnancy because it
can have a teratogenic effect on the fetus
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Client Teachings when taking
Phenytoins Instruct client to the suspension form well before
pouring
Advice client not to drive or perform otherhazardous activities when beginninganticonvulsant therapy. Until client adapts to drugdosage, drowsiness is likely to occur.
Alert female clients contemplating pregnancy toconsult with the health care provider because
phenytoin and valproic acid may have teratogeniceffect.
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During pregnancy, seizures frequently increase becauseof increased metabolism rates, and serum phenytoinlevels should be closely monitored. Mostanticonvulsants are classified pregnancy category D.
Inform client that alcohol and other CNS depressantscan cause an added depressive effect on the body andshould be avoided.
Teach the client not to abruptly stop the drug therapybut rather to withdraw the prescribed drug gradually
under medical supervision to prevent the seizurerebound (recurrence of seizure)
Teach the client not to take the OTC drugs without firstconsulting the health care provider.
Instruct the client with diabetes to monitor serumglucose levels more closely than usual because
phenytoin may inhibit insulin release, thus causing anincrease in blood sugar.
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DIET
Educate client to take the anticonvulsant at the
same time everyday with food or milk. If liquid
form is used, shake well before ingesting the
drug.
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Side Effects
Urine must be pinkish or reddish brown.
Maintain good oral hygiene and use a soft
toothbrush to prevent gum irritation and bleeding
Report symptoms of sore throat, bruising, and
nosebleeds, which may indicate a blood dyscrasia.
Inform any the health care provider of adverse
reactions such as gingivitis, nystagmus( involuntary movement of the eyeballs) slurred
speech, rash, and dizziness.
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Pharmacokinetics
Phenytoin s slowly absorbed from the small
intestine. It is a highly protein bound (85-95%)
drug; a decrease in serum protein or albumin caincrease the free phenytoin serum level. With a
mall amount to average drug dose, the half-life of
phenytoin is approximately 22 hours; however, the
range can be from 6-45 hours. Phenytoin ismetabolized to inactive metabolites, and that
portion is excreted in urine.
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Pharmacodynamics
The pharmacoynamics of orally administeredphenytoin include on set of action within 30
minutes to 2 hrs, peak serum concentrationon 1.5 to 3 hurs, steady state of serumconcentrationnin 7-10 days, and a durationof action dependent to half-life. Oral
phnytoin is most commonly ordered as asustained-release capsule. The peakconcentration time is 4-12hours .
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Pharmacodynamics
Intravenous (IV) infusion of phenytoin should beadministered by a direct injection into a large vein.The drug may be diluted in a saline solution;
however, dextrose solution should be avoidedbecause of drug precipitation. Continuous IVinfusion of phenytoin should not be used. IV
phenytoin, 50 mg in faction thereof, should be
administered over a period of 1 minute for adultsand, when the client is elderly, at a rate of 25 mg
per minute.
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Infusion rates of more than 50 mg per
minute may cause hypotension or
cardiac dysrhythmias, especiallywith older and debilitated clients
Local irritation at injection site of
phenytoin irritates tissues and maycause damage. For this reason and
because of its erratic absorption rate,
IM administration of phenytoin is
discouraged.
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2. Barbiturates
Phenobarbital, a long acting barbiturate, is still
prescribed to treat grand mal seizures and acute
episodes of status epilepticus seizures (rapid
succession epileptic seizures), meningitis, toxic
reactions, and eclampsia.
Problems associated with Phenobarbital include its
cause of general sedation and clients tolerance todrug.
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3. Succinimides
The succinimides drug groups is used to treat
absence or petit mal seizures, and it may be used in
combination with other anticonvulsants to treat
seizures.
Ethosuximide (Zarontin)- succinimide of choice
Methsuximide (Cebuntin) and Phensuximide
(Milontin)- used mainly for petit mal refractoryseizures
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4. Oxazolidones or
Oxazolodinedione
Oxazolidones, trimethadione, and
paramethadione are prescribed to treat petit
mal seizures.Prescribed more frequently than
paramethadione
May be used in combination with other drugsor singly to treat refractory mal seizures
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5. Benzodiazipines
3 benzodiapines that have anticonvulsants effects: Clonazepam- effective in controlling petit mal
(absence) seizures.
2. Clorazepate dipotassium- frequentlyadministered in adjunctive therapy for treating
partial seizures. Diazepam- primarily described for treating acute
status epilepticus and must e administered IV toadhere the desired response - has short term effect.
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6. Iminostilbenes
Carbamazepine- an iminostibene, is effective in
treating refractory seizures disorder that have not
responded to other convulsant therapies.
Use to control grand mal and partial seizures and
combination of these seizures.
Use also for psychiatric disorders, tnigeminal neuralgia,
and alcohol withdrawal.
Not approved by FDA for treatment of the above
mentioned disorder.
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7. Valproate
Valproic acid has been prescribed for petit
mal, grand mal and mixed types of seizures.
Care should be taken when giving this drugto very young children and clients with liver
disorders because of hepatoxicity is one of
the possible adverse reactions
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Anticonvulsants and
Pregnancy
During pregnancy, seizure episodes increase 25%in women with epilepsy.
Hypovia that may occur during seizures placeswoman with epilepsy and her fetus at risk.
Anticonvulsant drugs increase the loss of folate(folic acid) in pregnant women.
Tend to act as inhibitors of Vitamin K, whichcontributes to hemorrhaging in infants shortlyafter birth.
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Anticonvulsants and
Pregnancy Some anticonvulsants drugs have teranogenic properties
that increase the risk for fetal malformation.
1.Phenytoin and carbamazepine
- Linked to fetal anomalies such as cardiac defects andcleft palate.
2. Trimethadione
- should not be given to women bearing of child becauseof its strong teratogenic effect.
3. Valproic acid- causes neural tubal effect (spinal bifida) in 2% to 3% of
pregnant women who take the drug
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Anticonvulsant and Febrile
Seizures
Seizures associated with fever usually occur in
children between the ages of 3 months and 5
years. Epilepsy develops in app. 2.5% of children
who have had one or more febrile seizures.
Prophylactic anticonvulsants such as
Phenobarbital or diazepam may be indicated for
high risk client. Valproic acid should not be given to children
because of its possible hepatotoxic effects.
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Anticonvulsants and Status
Epilepticus
Status Epilepticus- a continuous seizure state,considered a medical emergency.
The choices of pharmacologic agents arediazepam (Valium) administered IV or lorazepam(Ativan) followed by IV administration of
phenytoin (Dilantin).
For continued seizures, midazoleum (Versed) orpropofol (Diprivan), then high-dose barbituratesare used. These drugs should be administeredslowly to avoid respiratory depression.
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Selected Anticonvulsants for
Seizure Disorders
Tonic-Clonic (Grand Mal) Phenytoin,
Carbamazepine, Fosphenytoin,
Lamotrigine, Primidone, Phenobarbital
Absence (Petit Mal) Ethosuximide,
Valproic Acid, Lamotrigine, Clonazepam
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Reporters
Judimer S. Bendita
Rafael C. Catbagan, Jr.
BSN 3B