Group 1 - Anticonvulsants

8/14/2019 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

Group 1 - Anticonvulsants

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