Pharmacology: Pharmacodynamics: Ciprofloxacin is a synthetic 4-quinolone derivative, with bactericidal activity. It acts via inhibition of bacterial DNA gyrase, ultimately resulting in interference with DNA function.
Ciprofloxacin is highly active against a wide range of Gram-positive and Gram-negative organisms and has shown activity against some anaerobes, Chlamydia spp. and Mycoplasma spp. Ciprofloxacin is also suitable for use in combination with penicillins, cephalosporins, aminoglycosides and tetracyclines where additive behaviour is usually observed. additive behaviour is usually observed.
Pharmacokinetics: Absorption of ciprofloxacin occurs rapidly, mainly from the small intestine (Abs. T1/2 = 2-15 min). Plasma levels are dose-related and peak 0.5-2.0 hrs after dosing. The AUC also increases dose proportionately after administration of both single and repeated oral doses. The oral bioavailability is approximately 70-80%. Distribution of ciprofloxacin within tissues is wide and the volume of distribution high, though slightly lower in the elderly. Protein binding is low ( between 19-40%).
Elimination of ciprofloxacin and its metabolites occurs rapidly, primarily by the kidney. After single dose of ciprofloxacin, 55% are eliminated by the kidney and 39% in the faeces within 5 days. The elimination half-life of unchanged ciprofloxacin over a period of 24 - 48 hrs post dose is 3.1-5.1 hrs.
Even though, studies with severely renally impaired patients (creatinine clearance < 20ml/ minute) do not give clear indications, it is recommended to reduce by half the total daily dose.
Results of studies in paediatric cystic fibrosis patients have shown dosages of 20 mg/kg orally twice daily is recommended to achieve plasma concentration/time profiles comparable to those achieved in the adult population at the currently recommended dosage regimen.