[Intracellular effects of josamycin]

Josamycin (Wilprafen) is accumulated in human polymorphonuclear leucocytes and monocytes (macrophages) by a factor of 12-20fold, in comparison with extracellular fluid. The uptake of the antibiotic by lymphocytes and erythrocytes is much less than with the two types of phagocytic cells. The distribution of 14C-josamycin was measured after lysing the polymorphonuclear leucocytes and the results confirmed that the antibiotic penetrates through the cell membrane and accumulates in the cytoplasm. The results indicate that josamycin is taken up into the cell by an active transport mechanism. It is significant for the clinical application of josamycin that the active drug is present inside the cells and can thus support the bactericidal activity of polymorphonuclear leucocytes or monocytes against intracellularly localized microorganism. This localization of the antibiotic in the two types of phagocytosing cells of the defense system could be important for the treatment of several infectious diseases.