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Pharmacology: Ch. 16 Anticonvulsants

Terms in this set (32)

Epilepsy
A group of disorders involving a chronic stereotyped recurrent attack of involuntary behavior or experience or changes in neurologic function caused by electrical activity in the brain that can be recorded via an electroencephalogram (EEG)

•Can be localized or generalized
Seizure etiology
• Affects 1% of the population
• infection
• trauma
• toxicity to exogenous agents
• genetic or birth influences
• circulatory disturbances
• metabolic or nutritional alterations
• neoplasms, hereditary factors, fevers, and degenerative diseases

•Most patients have idiopathic epilepsy; the cause is unknown
Generalized Seizures
• Consciousness is lost in both absence and tonic-clonic seizures
•Little movement occurs in absence seizures; major movement of large muscle groups occurs in tonic-
clonic seizures
•The patient may experience an aura before the onset of the seizure
•May be characterized by numbness, nausea, or
unusual sensitivity to light, odor, or sound
Absence Seizures (Petit Mal)
•Symptoms of absence seizures include a brief loss of consciousness with characteristic EEG waves and little movement
•Absence seizures usually begin during childhood and disappear during middle age
•The patient is usually unaware that these seizures are occurring, and body tone is not lost
•No aura or postictal state occurs
Tonic-Clonic Seizures
•Generalized tonic-clonic seizures include longer periods of loss of consciousness and major motor activity of the large muscles of the body
•The seizure begins by the body becoming rigid and the patient falling to the floor
•Tonic rigidity is followed by clonic jerking of the face, limbs, and body
•Finally, the patient becomes limp and comatose
•Consciousness gradually returns with postictal confusion, headache, and drowsiness
Status Epilepticus
•Status epilepticus seizures are continuous tonic-clonic seizures that last longer than 30 minutes or recur before the end of the postictal period of the previous seizure
•Status epilepticus seizures represent an emergency situation
•Rapid therapy is required, especially if the seizure activity has produced hypoxia
•Parenteral benzodiazepines, such as diazepam, are the drugs of choice to control this type of seizure
Partial (Focal) Epilepsies
•Partial epilepsies involve activation of only part of the brain, and the location of the activity determines the clinical manifestations
•The attack is called an elementary (simple) partial
attack when consciousness is not impaired
•The attack is termed a complex partial attack when consciousness is impaired
• Complex seizures are also called psychomotor or
temporal-lobe seizures
Drug Therapy of Patients with Epilepsy
•Drug therapy has variable efficacy, from complete control of all seizures to reducing the frequency of seizures
•Anticonvulsant agents may be used singly or in
combination
•These agents are central nervous system (CNS) depressantss* that attempt to prevent epileptic seizures without causing excessive drowsiness
•These agents prevent the spread of abnormal electric discharges in the brain
General Adverse Reactions to Anticonvulsant Agents
•Anticonvulsants have a narrow therapeutic index
•Most anticonvulsants stimulate liver microsomal enzymess* that metabolize themselves, other anticonvulsants, and other drugs that the patient may be taking
•The metabolism of anticonvulsants can saturate the liver microsomal enzymes
•At some point, when the enzymes become saturated, the metabolism converts to zero-order kineticss*, and the drug level can increase abruptly
Central Nervous System Depression
•Depressed CNS function is a common side effect of the anticonvulsant agents
•Tolerance often develops to these effects, whereas the anticonvulsant effect persists
•Behavior alterations are reported to include both hyperactivity and sedation
Gastrointestinal Distress
•Gastrointestinal (GI) distress, including anorexia, nausea, and vomiting, can occur with most anticonvulsants
•Effects can be minimized by taking the drug with food
Drug Interactions
•The most important drug interaction involves stimulation of the hepatic microsomal enzymes
•Inducing these enzymes results in a reduction in the blood levell* of the affected drugs
•Drug interactions with anticonvulsants are more significant than with other drug groups because of their narrow therapeutic indexes
Idiosyncratic drug reactions
•Dermatologic side effects: rash, Stevens-Johnson
syndrome, exfoliative dermatitis, and erythema multiforme
•Drug-induced systemic lupus erythematosus and hematologic effects have been reported
Drug interaction: Teratogenicity/growth:
•Several interactions have been implicated in production of fetal anomalies
•Associated with alteration in growth
Drug interaction: Withdrawl:
Abrupt withdrawal can precipitate seizures
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