Treatment of Epilepsy with Antiepileptic Drugs : Selecting the Proper Drug

Abstract

To achieve immediate control of a person undergoing a seizure, an early and effective antiepileptic drug (AED) therapy is required. In this regard, a monotherapy with a minimal dosage is always preferred, and as for the choice of drug, the main factor to consider is whether the drug's clinical effect is suited to the type of seizure or epilepsy manifested. Even so, several possible choices are usually available, often between drugs presenting only subtle differences with respect to their efficacy. This fact, combined with the need for long-term treatment, makes the drug's possible toxicity a key issue. Further, to some degree the choice of drug may also be influenced by personal opinion or previous experience. Given these considerations, drugs that can be efficacious for major types of seizures are herein described and discussed. Phenytoin (PHT), in contrast to most AEDs, follows a zero order kinetics or, in other wouds, a culvilinear relationship between the dose and the serum level. The curve breaks in the area of the therapeutic level, which means that even minor changes in the dosage may cause disproportionately large changes in the serum level, so that the amount of the daily PHT dose may require minor adjustment. Turning to another drug, carbamazepine (CBZ) induces its own metabolism (autoinduction) , so that unusually high levels of CBZ may be obtained for the first 1 or 2 weeks of treatment compared to those of chronic patients. Therefore when using CBZ, it is important to monitor the doses being provided to avoid acute toxicity. Valproate (VPA) is another drug to consider. When treating epileptic women of child bearing age, conven-tional formulations of valproate should be replaced with a controlled release VPA formulation because of the risk of malformations occurring in the newborn, since a correlation has been found between a high VPA serum level and newborn malformations. Failing to take the medication as prescribed is a major reason for poor seizure control, and methods to determine non-compliance are discussed. AEDs possess a great potential for interacting with each other and with other drugs. Therefore when prescribing other drugs to AED patients, it is important to make them aware of the risks of interactions. Complete seizure control should never be the sole goal. Problems to be considered are how the seizures ultimately affect the patient's quality of life and whether the prescribed AEDs will eliminate further seizures.