HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC SEPARATION AND IDENTIFICATION OF EPIMERIC 17-KETONE IMPURITIES IN COMMERCIAL SAMPLE OF DEXAMETHASONE SODIUM-PHOSPHATE

A commercial sample of dexamethasone sodium phosphate solution for injection was found to contain 56% of the label concentration and to be extensively contaminated (∼50%) with a white insoluble solid, which was identified as a mixture of the 16α‐ and 16β‐methyl epimers of 9‐fluoro‐11β‐hydroxy‐16‐methylandrosta‐1,4‐diene‐3,17‐dione. High‐performance liquid chromatography (HPLC) was used to separate, identify, and quantitate these epimers and to determine their presence in commercial samples. One epimer was identified by HPLC comparison with a synthesized specimen of 9‐fluoro‐11β‐hydroxy‐16α‐methylan‐drosta‐1,4‐diene‐3,17‐dione. The second peak was identified as the 16β‐epimer by epimerization of the synthesized α‐component with alkali to obtain a product whose chromatogram matched that of the impurity. These conclusions are supported by data obtained by IR and UV spectrophotometry, TLC, and the blue tetrazolium test. Copyright © 1979 Wiley‐Liss, Inc., A Wiley Company