Dynamic aspects of the activity of clofazimine against Mycobacterium intracellulare.

The interaction of clofazimine with M. intracellulare was studied using the in vitro dialysis model and the membrane filtration technique. With the in vitro model, clofazimine when it was inside the bag at 3 micrograms/ml or more exerted a bactericidal action within 6 days. On the other hand, when the drug concentration in the outside medium was gradually raised from 1 microgram/ml to 3 micrograms/ml over a period of 5 days, it produced only a bacteriostatic effect. Using the membrane filter technique, exposure of M. intracellulare to 1 microgram/ml of clofazimine for 24 and 48 hours induced lag periods of 24 and 168 hours respectively.