Sustained release properties of an intra-adiposely administered dapsone depot injection

A dapsone depot injection, consisting of dapsone crystals of bipyramidal shape with a particle size of 38 micron-63 micron suspended in an aqueous vehicle, appeared to result in different concentration/time profiles in men and women when delivered "intramuscularly." This phenomenon can be explained by the larger skin-to-muscle distance in women than in men. Injections intended to be delivered intramuscularly are, in fact, administered into subcutaneous fatty tissue in most of the women. Because sustained release properties were more satisfactory in women than in men, in this study the absorption of dapsone was investigated after administration of the same injection into gluteal fatty tissue. Via this route of administration, for which the term intra-adipose is used, 12 female and 15 male healthy volunteers received 1000 mg dapsone, after which blood samples were taken at regular intervals for 35 days to determine dapsone and monoacetyldapsone concentrations in serum using high-pressure liquid chromatography with fluorometric detection. No important differences between men and women appeared to exist at any time point after injection. The peak concentrations were 0.69 +/- 0.40 mg/l in men and 0.84 +/- 0.31 mg/l in women. No important side effects were observed, either locally or systemically. Volunteers who previously received an intramuscular injection preferred the intra-adipose administration. The good depot properties and better acceptance of intra-adipose dapsone administration are reasons to prefer this route of administration.