Plasma concentration/time curve of erythromycin after a 12-hour intravenous infusion of erythromycin lactobionate in man.

As the pharmacokinetics after a slow infusion had not previously been evaluated in the doses used in this study, it was decided to measure the plasma concentration/time curve after a twelve-hour intravenous infusion of 2·0 g of erythromycin lactobionate in 2 litres of 0·9% normal saline. Six healthy medical students with no past history of cardiovascular, renal, hepatic, metabolic or gastrointestinal disease and no past drug allergy participated. The concentration of erythromycin base in venous blood was measured by small plate microbiological assay. Venous blood was taken at zero, 15, 30, 45, 60 min and at 2, 3, 4, 6, 8, 12, 16, 20 and 24 hr after starting the infusions. Duplicate assays were performed on all plasma samples at Guy's and at the manufacturer's laboratories. A full haematological and biochemical screening profile was performed before and after the study. The mean ± s.e. plasma erythromycin base concentration rose from 0·7 ± 0·2 μg/ml at 15 min to 6·06 ± 1·6 μg/ml at 1 hr. The peak plasma concentration was between 1·48 ± 0·25 μg/ml at 30 min and 7·21 ± 0·93 μg/ml at 4 hr. The plasma concentration at 12 hr was 6·17 ± 0·33 μg/ml, and fell to 0·37 ± 0·05 μg/ml at 24 hr. These findings suggest that therapeutically effective plasma concentrations follow a slow intravenous infusion of erythromycin lactobionate. There was no evidence of adverse haematological or biochemical function in the tests of blood, hepatic or renal function, apart from two volunteers who vomited after the infusions were discontinued.