Pharmacokinetics of cefazolin in skin following iontophoretic administration in a rabbit model

The purpose of this thesis was to study the pharmacokinetics of cefazolin in skin following iontophoretic administration by using a stainless-steel patch. Cefazolin is a first generation cephalosporin antibiotic.;FDA labeled indication of cefazolin includes treatment of skin infections. The pharmacokinetic behavior of cefazolin in skin is poorly studied. Cefazolin is mainly used to treat bacterial infections of the skin. It has been observed that cefazolin sodium is used for skin or soft tissue infection, cutaneous bacillus anthracis and bacterial infection caused due to S. aureus (including (beta-lactamase-producing strains), S. pyogenes, and other strains of streptococci. There is no topical or transdermal preparation of cetazolin in the market. The main purpose of my thesis was to find out whether the cefazolin can be administered by iontophoresis and can each up to effective concentration against the Staphylococcus aureus or Streptococcus pyogenes. If the concentration in the skin reaches to MIC (Minimum Inhibitory Concentration) then there are chances that drug may have further dermatological action. The MIC of cefazolin in the skin is 0.25 to 1.0 mug/ml for the infection cause by Staphylococcus aureus and Streptococcus pyogenes and 1.0 to 4.0 mug/ml for the infection cause by E. coli. To monitor target site concentrations in rabbit skin microdialysis technique was used, which allows sequential sampling over time.;Iontophoresis is a penetration enhancer technique that uses a mild electrical current to increase the penetration of charged ions through the skin. Since cefazolin is ionized at physiological pH it looks like a suitable candidate for iontophoretic delivery. Microdialysis is a semi-invasive separation technique that allows the sampling or the delivery of molecules in vivo, according to the concentration gradient between the solution perfusing the probe and the extracellular fluid surrounding it. Owing to selective access to the target site for most anti-infective drugs, microdialysis satisfies regulatory requirements for pharmacokinetic distribution studies and has become a reference technique for tissue distribution studies.;The HPLC method selected and validated for the cefazolin in microdialysis samples consisted of a reversed phase C18 column, flow rate of 0.8 ml/min and a detection wavelength of 273 nm. Mobile phase used for microdialysis consisted of 90% 0.05 M phosphate buffer (pH 5) and 10% Acetonitrile. The retention time was 8.26 min. The calibration curves for microdialysis samples were linear in the range of 0.5 to 50 mug/ml with a correlation coefficient larger than 0.99. The lower limit of quantification (LLOQ) was 0.5 mug/ml. The kinetics of cefazolin was investigated in 3 female pathogen-free New Zealand albino rabbits. Microdialysis probes were implanted into the upper dorsal shaved skin of a tranquilized rabbit and perfused with lactated Ringer's solution. Patches donated by Dr. Phillip Friden (Transport Pharmaceuticals, Framingham, MA) were used to deliver cefazolin for 60 min at different current densities (50, 75, 100, and 125 muA/cm2) on different occasions in a randomized cross-over experimental design in same dose. Microdialysis samples were collected at selected time intervals. Retrodialysis was performed at the start of each experiment to assess probe recovery and correct the dialysate concentration to reflect the actual interstitial fluid concentration.;The results show that measurable cefazolin concentrations were reached immediately after the onset of the current in the skin. There is not a significant concentration of cefazolin in skin has been reached for current densities 50 muA/cm2, but it reaches to MIC for a considerable time for current densities of 75, 100, and 125 muA/cm2. Though there was no so considerable difference in Cmax and AUC across the different current densities of 75, 100, and 125 muA/cm2, this study indicates the possibility of transdermal delivery of cefazolin by iontophoresis.