Central Nervous System Regulation, Mood, and Cognition
Central Nervous System Regulation, Mood, and Cognition
8.10 Anticonvulsants
Open Resources for Nursing (Open RN)
Medications used for seizures are called anticonvulsants or antiseizure drugs. Antiseizure drugs stabilize cell membranes and suppress the abnormal electric impulses in the cerebral cortex. These drugs prevent seizures but do not provide a cure. Antiseizure drugs are classified as CNS depressants. There are many types of medications used to treat seizures such as phenytoin, phenobarbital, benzodiazepines, carbamazepine, valproate, and levetiracetam.[1]
There are three main pharmacological effects of antiseizure medications. First, they increase the threshold of activity in the motor cortex, thus making it more difficult for a nerve to become excited. Second, they limit the spread of a seizure discharge from its origin by suppressing the transmission of impulses from one nerve to the next. Third, they decrease the speed of the nerve impulse conduction within a given neuron.
Some drugs work by enhancing the effects of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), which plays a role in regulating neuron excitability in the brain.[2] Gabapentin, although structurally similar to GABA and classified as an anticonvulsant, is commonly used to control chronic neuropathic pain. Neuropathic pain is defined by the International Association for the Study of Pain as “pain caused by a lesion or disease of the somatosensory nervous system.”[3] An example of neuropathic pain is tingling or burning in the lower extremities that often occurs in clients with diabetes.
Phenytoin
Phenytoin, which was discovered in 1938, was the first anti-seizure medication and is still being used to control seizures.[4]
Mechanism of Action
Phenytoin improves evidence of seizures by interfering with sodium channels in the brain, resulting in a reduction of sustained high-frequency neuronal discharges.
Indications for Use
Phenytoin is indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures and for the prevention and treatment of seizures occurring during or following neurosurgery.
Nursing Considerations Across the Lifespan
Phenytoin should not be administered to pregnant women because it will cause harm to the fetus. When given intravenously, there is a Black Box Warning that the rate of administration should not exceed 50 mg per minute in adults and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) in pediatric clients because of the risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering intravenous phenytoin.
Phenytoin has a narrow therapeutic drug level, usually between 40 – 80 uM/L, so serum drug monitoring is required.[5]Serum levels of phenytoin sustained above the therapeutic range may produce confusional states referred to as delirium, psychosis, or encephalopathy. Accordingly, at the first sign of acute toxicity, serum levels should b