FIG. 4.

Release characteristics of small and large rifampin-loaded microspheres in mice. One group of mice received an oral gavage of rifampin daily (10 mg/kg) (○) from day 0 to day 25. Another group of mice was injected intraperitoneally with 50 mg of the small-microsphere formulation S6 (1.4% [wt/wt] rifampin) (●), on day 0 and on day 7. A third group of mice was injected subcutaneously with 100 mg of the large-microsphere formulation 6 (27% [wt/wt] rifampin) (■), on day 0. Additive means for plasma rifampin levels with small and large microspheres (▵) are also given. At 7, 14, and 21 days, plasma was assayed for rifampin by using the bioassay described in Materials and Methods.