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 Bayers 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. Society and culture
Cost
It is available as a generic medication and not very expensive. At least one company, Turtle Pharma Private Limited provides industrial-size amounts

Generic equivalents
On 24 October 2001, the Prescription Access Litigation (PAL) project filed suit to dissolve an agreement between Bayer and three of its competitors which produced generic versions of drugs (Barr Laboratories, Rugby Laboratories, and Hoechst-Marion-Roussel) that PAL claimed was blocking access to adequate supplies and cheaper, generic versions of ciprofloxacin.
However, ciprofloxacin may be taken with dairy products or calcium-fortified juices as part of a meal.Ciprofloxacin inhibits the drug-metabolizing enzyme CYP1A2 and thereby can reduce the clearance of drugs metabolized by that enzyme. CYP1A2 substrates that exhibit increased serum levels in ciprofloxacin-treated patients include tizanidine, theophylline, caffeine, methylxanthines, clozapine, olanzapine, and ropinirole. Co-administration of ciprofloxacin with the CYP1A2 substrate tizanidine (Zanaflex) is contraindicated due to a 583% increase in the peak serum concentrations of tizanidine when administered with ciprofloxacin as compared to administration of tizanidine alone. Use of ciprofloxacin is cautioned in patients on theophylline due to its narrow therapeutic index. The authors of one review recommended that patients being treated with ciprofloxacin reduce their caffeine intake. Evidence for significant interactions with several other CYP1A2 substrates such as cyclosporine is equivocal or conflicting.The Committee on Safety of Medicines and the FDA warn that central nervous system adverse effects, including seizure risk, may be increased when NSAIDs are combined with quinolones. The mechanism for this interaction may involve a synergistic increased antagonism of GABA neurotransmission.Altered serum levels of the antiepileptic drugs phenytoin and carbamazepine (increased and decreased) have been reported in patients receiving concomitant ciprofloxacin.Ciprofloxacin is a potent inhibitor of CYP1A2, CYP2D6, and CYP3A4. 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.