Quinolone Antibacterials

Quinolone Antibacterials

INTRODUCTION

Quinolones constitute a large class of synthetic antimicrobial agents that are highly effective in the treatment of many types of infectious diseases, particularly those caused by bacteria. Quinolones are potent, broad-spectrum antibacterial agents. The early congeners (nonfluorinated at C-6 position, such as nalidixic acid) were limited to certain gram-negative infections, such as urinary tract infections. However, the modern generation of fluoroquinolones, containing C-6 fluoro substituent and a cyclic basic amine moiety at C-7 position, surpass their predecessors in terms of spectrum of activity and potency. This has allowed for their use against a variety of gram-negative as well as some gram-positive pathogens.

Many analogues have piperazino groups on C-7 because of which they broaden the spectrum, especially to gram-negative organisms, such as Pseudomonas aeruginosa, however, they also increase the affinity of the compound for the gamma-aminobutyric acid (GABA) receptor, which contributes to central nervous system (CNS) side effects. Quinolones are easily prepared and administered via parenteral and oral routes, and are well tolerated.

Mode of action: Quinolones inhibit the action of bacterial DNA gyrase enzyme. This enzyme is responsible for supercoiling and compacting bacterial DNA molecules into the bacterial cell during replication. This action is accomplished by modifying the topology of DNA via supercoiling and twisting of these macromolecules to permit DNA replication or transcription.