Absorption of erythromycin acistrate and erythromycin base in the fasting and non-fasting state

Absorption of erythromycin acistrate (EA) and two erythromycin base (EB) preparations (enterotablet A and B) taken after an overnight fast or immediately before a standard breakfast was studied in 29 healthy volunteers in three separate studies, in a cross-over, randomized design. In Study I, the absorption of a single dose (400 mg) of EA was similar in the fasting and non-fasting state. There was, however, more interindividual variation and in two subjects absorption was markedly impaired in the presence of food. Cimetidine given at two doses (400 + 800 mg) had no effect on the pharmacokinetics of erythromycin acistrate. In Study II, the effect of food on the bioavailability of the two EB preparations was studied after a single dose of 500 mg (2 x 250 mg enterocoated tablets) and after multiple dosing (2 x 250 mg tid). When given with a standard breakfast, erythromycin base was significantly better absorbed from enterotablet A than from enterotablet B, whether given as a single dose or in repeated doses. Study III followed the same design as Study II except that the tablet size of both enterotablets A and B was now 500 mg. Even in this study the absorption of enterotablet A was significantly better than that of enterotablet B. EA is adequately absorbed when taken before a meal. Cimetidine does not interfere with its elimination. Concomitant food intake produced considerably dissimilar absorption of two commercially available enterocoated EB preparations. Although at steady-state this was less prominent than after a single dose, it may have some clinical significance.