To the Editor.—
Although it is well known that plasma levels are better than dosages in the assessment of clinical response to phenytoin, it is probably less widely recognized that the values of such levels given in textbooks and in the Physician's Desk Reference (PDR) are below the therapeutic range for some patients.1,2I recently treated a patient suffering from psychomotor seizures with increasing doses of phenytoin, deliberately aiming for the higher plasma levels recorded in the literature before considering a change to another medication.Despite the absence of side effects, early signs of toxicity, or abnormalities in serial laboratory investigations (blood chemistry, hematology tests, ECG), the patient's rising levels of phenytoin were paralleled by the anxiety and panic of nurses, resident house staff, and fellow attending physicians, who were all concerned about this departure from "the Gospel according to PDR."As a result of the ensuing hue and
Adebimpe VR. Individualization of Phenytoin Therapy. JAMA. 1976;236(26):2943. doi:10.1001/jama.1976.03270270005013
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