The penetration of erythromycin into human bronchial mucosa.

1 In this paper the pharmacokinetic relation between concentrations of erythromycin in plasma and in bronchial mucosa was established. 2 Sixteen patients undergoing bronchoscopy received 1 g erythromycin by continuous infusion in 30 min. 3 Two bronchial mucosal samples were taken from each patient sometime after drug administration. Concentrations were determined in the mucosal sample and in several plasma samples collected at different times before the mucosal sample. 4 Rate constants for the distribution between plasma and tissue were calculated on the basis of the assumption of passive diffusion of the free drug. 5 Mean values of the distribution rate constants, calculated by a nonlinear curve fitting procedure, were 2.40 h-1 for distribution from plasma to tissue and 1.28 h-1 for that from tissue to plasma. 6 These values correspond to a half-life for the distribution of the free drug of 33 min and a free fraction of the drug in mucosal tissue of 0.20.