Blood tests are often checked before treatment with an antiepileptic drug (AED) begins. These results can then be compared with blood tests that are done after you have been taking the AED for some time, to see if there have been any changes.
These tests include measurements of electrolyte levels (chemicals in the blood such as sodium and potassium), liver and kidney function tests, blood-cell counts, and monitoring of antiepileptic drug levels.
The frequency of testing varies considerably from doctor to doctor and even country to country. In the United States, blood tests are often done routinely several weeks or months after a new drug is started. The timing of later tests depends on the patient's medical history, the drug and, most importantly, the doctor's opinion on the necessity for testing.
The so-called therapeutic range of blood levels for antiepileptic drugs is the range of levels at which most patients have good seizure control and few or no adverse effects. The lower and upper limits of this range can vary between different laboratories and doctors.
Checking the blood level of a drug at consistent times of day and consistent times after the last dose of medication is taken allows the doctor to compare levels at different dosages. Routine blood levels are best measured when the amount of the drug in the bloodstream is at its lowest point, which is called the trough level. This generally corresponds to the time just before the medication is taken.
No. Seizure control without adverse effects, not the blood drug level, is the criterion for judging the efficacy of treatment. For example, if a patient's seizures are well controlled but the level of drug in the blood is below the expected therapeutic range, the doctor will usually be satisfied and will not increase the dosage to raise the blood drug level.
Topic Editor:Steven C. Schachter, M.D.
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