Effects of penicillin on clinical tests with special reference to serum albumin measured by a modified BCP method

Penicillin derivatives are widely used for treatment of bacterial infection. A high-dose penicillin is recommended as a first choice particularly for infective endocarditis in the guideline from the American Heart Association. We found two patients with infective endocarditis who had serum albumin shifting to a cathode side on the electrophoresis. The both patients had been treated with a high-dose penicillin G. The serum albumin concentrations of the patients were 1.7 g/dL and 1.8 g/dL when measured by a modified bromocresol purple (BCP) method while they were 3.4 and 3.3, respectively, by a bromocresol green (BCG) method. To confirm these low values obtained by the modified BCP method are due to the high-dose penicillin G therapy, we added penicillin G in normal sera and measured albumin concentration by the BCP and BCG methods. Exogenously added penicillin G inhibited the BCP reaction in dose-dependent and incubation time-dependent manners but not the BCG reaction. Here, we generally describe effects of penicillin derivatives on serum albumin measurement and other clinical tests.