neurologic disorders
Antiseizure Medications
Principles of Long Term Treatment
There are some general principles for using antiseizure medications (also called antiepileptic medications or anticonvulsants): A single medication, usually the first or second one tried, controls epileptic seizures in about 60% of patients. If seizures are difficult to control from the outset (in 30 to 40% of patients),≥2 medications may eventually be required. If seizures are intractable (refractory to an adequate trial of≥2 medications), patients should be referred to an epilepsy center to determine whether they are candidates for surgery. Some medications (eg,phenytoin, valproate), given IV or orally, reach the targeted therapeutic range very rapidly. Others (eg,lamotrigine,topiramate) must be started at a relatively low dose and gradually increased over several weeks to the standard therapeutic dose, based on the patient’s lean body mass. Dose should be tailored to the patient’s tolerance of the medication. Some patients have symptoms of medication toxicity when blood levels of a medication are low; others tolerate high levels without symptoms. If seizures continue, the daily dose is increased by small increments. The appropriate dose of any medication is the lowest dose that stops all seizures and has the fewest adverse effects, regardless of blood level of a medication. Blood levels of medications are only guidelines. Once medication response is known, following the clinical course is more useful than measuring blood levels. Determine the medication dose using clinical criteria (the lowest dose that stops seizures and has the fewest adverse effects), regardless of blood levels. If toxicity develops before seizures are controlled, the dose is reduced to the pretoxicity dose. Then, another medication is added at a low dose, which is gradually increased until seizures are controlled. Patients should be closely monitored because the 2 medications can interact, interfering with either medication’s rate of metabolic degradation. The initial medication is then slowly tapered and eventually withdrawn completely. Use of multiple medications should be avoided if possible because incidence of adverse effects, poor adherence, and medication interactions increases significantly. Adding a second medication helps about 10% of patients, but incidence of adverse effects more than doubles. The blood level of antiseizure medications is altered by many other medications, and vice versa. Physicians should be aware of all potential drug-drug interactions before prescribing a new medication. Once seizures are controlled, the medication should be continued without interruption until patients have been seizure-free for at least 2 years. At that time, stopping the medication may be considered. Most of these medications can be tapered by 10% every 2 weeks. Relapse is more likely in patients who have had any of the following: A seizure disorder since childhood Need for > 1 medication to be seizure-free Previous seizures while taking an antiseizure medication Focal-onset or myoclonic seizures Underlying static (nonprogressive) encephalopathy Abnormal electroencephalogram (EEG) results within the last year Structural lesions (seen on imaging studies) Patients who have a relapse when they are not taking antiseizure medications should be treated indefinitely. 