Ciprofloxacin subclass of quinolones
Mechanism of action
Ciprofloxacin is a broad-spectrum antibiotic of the fluoroquinolone class. It is active against some Gram-positive and many Gram-negative bacteria. It functions by inhibiting a type II topoisomerase (DNA gyrase) and topoisomerase IV, necessary to separate bacterial DNA, thereby inhibiting cell division. Bacterial DNA fragmentation will occur as a result of inhibition of the enzymes.Usage
Ciprofloxacin is the most widely used of the second-generation quinolones. In 2010, over 20 million prescriptions were written, making it the 35th-most-commonly prescribed generic drug and the 5th-most-commonly prescribed antibacterial in the U.S.History
The first members of the quinolone antibacterial class were relatively low-potency drugs such as nalidixic acid, used mainly in the treatment of urinary tract infections owing to their renal excretion and propensity to be concentrated in urine. In 1979, the publication of a patent filed by the pharmaceutical arm of Kyorin Seiyaku Kabushiki Kaisha disclosed the discovery of norfloxacin, and the demonstration that certain structural modifications including the attachment of a fluorine atom to the quinolone ring leads to dramatically enhanced antibacterial potency. In the aftermath of this disclosure, several other pharmaceutical companies initiated research and development programs with the goal of discovering additional antibacterial agents of the fluoroquinolone class.
The fluoroquinolone program at Bayer focused on examining the effects of very minor changes to the norfloxacin structure. In 1983, the company published in vitro potency data for ciprofloxacin, a fluoroquinolone antibacterial having a chemical structure differing from that of norfloxacin by the presence of a single carbon atom. This small change led to a two- to 10-fold increase in potency against most strains of Gram-negative bacteria.  Importantly, this structural change led to a four-fold improvement in activity against the important Gram-negative pathogen Pseudomonas aeruginosa, making ciprofloxacin one of the most potent known drugs for the treatment of this intrinsically antibiotic-resistant pathogen.The oral tablet form of ciprofloxacin was approved in October 1987, just one year after the approval of norfloxacin. In 1991, the intravenous formulation was introduced. Ciprofloxacin sales reached a peak of about 2 billion euros in 2001, before Bayer's patent expired in 2004, after which annual sales have averaged around €200 million.The name probably originates from the International Scientific Nomenclature: ci- (alteration of cycl-) + propyl + fluor- + ox- + az- + -mycin.
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