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Pharmacology: Pharmacokinetics: Ciprofloxacin upon ingestion, is readily absorbed in the gastrointestinal tract. Peak plasma concentration of 2.5 mcg/mL is reached 1 to 2 hours after 500 mg oral dose. The oral bioavailability of the drug is about 70%.
Absorption of the drug may be delayed by food but it does not give significant clinical effects. The plasma half life of ciprofloxacin is 3.5 to 4.5 hours and may be delayed in patients with end-stage renal disease (8 hours) and in the elderly. In patients with severe liver cirrhosis, half life is slightly prolonged.
Ciprofloxacin is 20-40% protein bound. It is widely distributed in body and tissues. It may be seen in the cerebrospinal fluid, 10% in normal meninges, and is able to cross the placenta.
Ciprofloxacin is found to be excreted in breast milk but is mainly excreted in the urine by active tubular secretion and glomerular filtration which may be reduced by probenecid. Other means of elimination include hepatic metabolism, excretion in the bile where high concentrations are achieved, and transluminal excretion in the intestinal mucosa.
The urinary metabolite of ciprofloxacin is oxociprofloxacin and primary fecal metabolite is suphociprofloxacin. Oral ciprofloxacin is 40-50% and 15% is excreted in the urine as unchanged drug and metabolite, respectively, within a period of one day. Fecal excretion involves 20-35% of ciprofloxacin taken orally.
Few amounts of the drug may be removed by dialysis.
Microbiology: Ciprofloxacin is a bactericidal agent which inhibits an essential step in the reproduction of bacterial DNA, the A subunit of DNA gyrase (topoisomerase).
Ciprofloxacin is more potent and has a broader spectrum of activity than nalidixic acid, a non-fluorinated quinolone.
Spectrum: Ciprofloxacin is active against (Gram-negative aerobic bacteria) Enterobacteriaceae including Escherichia coli and Citrobacter, Enterobacter, Klebsiella, Proteus, Providencia, Salmonella, Serratia, Shigella, Yersinia spp., Pseudomonas aeruginosa, Hapnia, Edwardsiella, Morganella, Acinetobacter spp., Campylobacter spp., Gardnerella vaginalis, Helicobacter pylori, Legionella spp., Aeromonas, Plesiomonas Pasterurella multocida and Vibrio spp. Ciprofloxacin has variable activity against Brucella melitensis.
Gram-positive aerobic staphylococci bacteria including penicillinase-producing and non-producing strains as well as some methicillin-resistant strains are susceptible to ciprofloxacin. Streptococcus pneumoniae and enterococci are less susceptible to the drug.
Ciprofloxacin is also active against Corynebacterium spp. and Listeria monocytogenes.
It exerts bactericidal effect against Pseudomonas spp., Haemophilus ducreyi, H. influenzae, Moraxella (Branhamella) catarrhalis, Neisseria gonorrhea, N. meningitidis. This is also true to beta-lactamase producing strains of H. influenzae, M. catarrhalis, and N. gonorrhea.
Mycobacteria, mycoplasma, rickettsias, Plasmodium falciparum and Clostridium difficile may be sensitive to ciprofloxacin. Moderate susceptibility to ciprofloxacin is exhibited by Chlamydia trachomatis.
Resistance: Bacteroides fragilis, Clostridium difficile, other anaerobic bacteria, Campylobacter spp., non-typhoid Salmonella spp., multi-resistant Salmonella typhii, S. paratyphi, and beta-lactamase-producing gonococcus are resistant to ciprofloxacin. Ciprofloxacin is also inactive against fungi and the spirochete, Treponema pallidum.
Nocardia asteroides, Ureaplasma urealyticum, are usually considered to be resistant to ciprofloxacin.
During treatment with ciprofloxacin, resistant strains of Staphylococcus aureus (including meticillin-resistant strains), Pseudomonas aeruginosa, Enterobacteriaceae including Escherichia coli and Serratia marcescens were found.
Monotherapy with ciprofloxacin was reported to have caused the development of mutational resistance in mycobacteria.
Cross resistance exists between ciprofloxacin and other fluoroquinolones.
Resistance of Staphylococcus epidermidis to ciprofloxacin may have been caused by the presence of the drug in sweat.
Effect when given with other antimicrobial agents: Enhanced effect is exhibited when ciprofloxacin is given with imipenem against Pseudomonas aeruginosa. The activity of ciprofloxacin against Staphylococcus aureus and P. aeruginosa is enhanced if given with aminoglycosides. The same is true against anaerobic bacteria if given concomitantly with clindamycin or cefotaxime.
