Reassessing the lower end of the phenytoin therapeutic range: a review of the literature.

OBJECTIVE: To critically review available data on the effective lower end of the phenytoin therapeutic range for the treatment of seizure disorders. DATA SOURCES: Relevant articles were identified from an English-language search of MEDLINE 1982-1992. Additional references were found in bibliographies of these articles. STUDY SELECTION/DATA EXTRACTION: We reviewed articles that included data on serum phenytoin concentrations (SPCs) and seizure control. Data on concurrent anticonvulsants, seizure diagnosis, and seizure severity were extracted when available. DATA SYNTHESIS: The original study defining the phenytoin therapeutic range as 10-20 mg/L is analyzed; it was based on a small, homogeneous sample that cannot be generalized to a more diverse epileptic population. Many studies report patients obtaining seizure control with SPCs below 10 mg/L. Studies including a range of seizure diagnoses and severity have a larger variability in effective SPCs; however, effective SPCs are reproducible. CONCLUSIONS: The therapeutic range of phenytoin is defined on an individual basis. Some patients, especially those with infrequent, primary tonic-clonic seizures, may be controlled with phenytoin concentrations below the recognized reference range of 10-20 mg/L.

Role of a pharmacist in a seizure clinic.

The involvement of a clinical pharmacist in a Department of Veterans Affairs seizure clinic is described. A pharmacist who had served a residency in ambulatory care began working in a seizure clinic in 1988 after obtaining the cooperation of a neurologist interested in a multidisciplinary approach to patient care. A clinical protocol was developed to guide the pharmacist's participation. The seizure clinic is staffed by the clinical pharmacist, a pharmacy resident, and a neurologist and is currently treating 162 adult male veterans. Of the 162 patients, 159 are receiving anti-convulsant therapy. The role of the pharmacist is to assist the neurologist in providing patient-care services. The pharmacist interviews each patient, performs a neurological assessment and mental status evaluation, and orders laboratory tests. Information is recorded by the pharmacist on a history form and a subjective and objective assessment and planning form. The pharmacist presents the findings to the neurologist, and the patient is then interviewed jointly by the pharmacist and the neurologist. Between appointments, the pharmacist follows up on abnormal laboratory test values and informs patients of any necessary dosage adjustments. More time is available for patient care, there has been an increase in the detection of adverse drug reactions and disease states, and record keeping has improved. A pharmacist assumed a primary-care role in a seizure clinic by interviewing and assessing patients, ordering laboratory tests, and participating in the selection and adjustment of anticonvulsant therapy.

Amoxapine-induced tardive dyskinesia.

A case report of amoxapine-induced tardive dyskinesia following discontinuation of amoxapine therapy is reported. During 68 weeks of therapy, the patient received a maximum of amoxapine 400 mg/d. Six months after amoxapine discontinuation, the patient continued to have symptoms of tardive dyskinesia. These symptoms correlate with the dopamine receptor-blocking property of amoxapine and its metabolites. We propose that amoxapine therapy be monitored for the long-term as well as the short-term adverse effects of dopamine receptor-blockade.