An in vivo-in vitro comparison of the 2- and 3-phosphate esters of clindamycin.

Culture Streptomyces coelicolor Muller NRRL3532 deactivates clindamycin. The inactive compound identified as clindamycin-3-phosphate on treatment with dephosphorylating enzymes affords the active compound, clindamycin. In as much as the 2-phosphate ester of clindamycin is being clinically evaluated as an injectable form of clindamycin, it was of interest to compare its in vitro and in vivo characteristics with the 3-phosphate ester. Analysis of the kinetics of hydrolysis of the esters in three in vitro enzyme systems indicate marked differences, with the 3-ester being hydrolyzed much more slowly and much less extensively than the 2-ester. An in vivo study in rats revealed lower blood levels for the 3-phosphate when compared with the 2phosphate and may be related to the rates of hydrolysis. Metabolism studies indicate that the esters are metabolized in a similar manner to the parent clindamycin.