The book deals with the metal complexes of Azithromycin, a macrolide and gemifloxacin, fourth generation fluoroquinolone antibacterial which were synthesized characterized and their antimicrobial activities against various Gram negatives, Gram positives and antifungal species were analyzed. Interaction of gemifloxacin with co-administered drugs was also studied and for this purpose their methods on RP-HPLC were developed for the first time. To support these findings gemifloxacin derivatives were synthesized and characterized by physicochemical and spectroscopic methods with above mentioned interacting drugs. Gemifloxacin analogues were synthesized with different aromatic and aliphatic amines, amides, carboxylic acid, and phenols. In this work, we focused on C-3 and C-7 positions of gemifloxacin. The target derivatives were characterized by FT-IR, 1HNMR and mass spectrometry. Antimicrobial and antifungal activity of these newly synthesized analogues was also carried out. Enzymatic inhibition activities of all synthesized derivatives were also carried out against two different enzymes including urease, and ?-chymotrypsin. The test showed low to moderate activity against both enzymes.