Journal of the American Geriatrics Society
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In 15 elderly patients who had seizure disorders, venous blood (standard venipuncture) was compared with capillary blood (finger lancet puncture) as the source of the specimen for determination of serum phenytoin concentration. The values obtained by the two procedures were similar (r = 0.99). ⋯ Either method provides an adequate blood sample for determination of phenytoin, and both may be used interchangeably. Capillary samples may be preferable for aged patients in whom venipuncture proves difficult or painful.