Tissue Penetration and Pharmacokinetics of Tigecycline in Diabetic Patients with Chronic Wound Infections Described by Using In Vivo Microdialysis

Tissue penetration of systemic antibiotics is an important consideration for positive outcomes in diabetic patients. Herein we describe the exposure profile and penetration of tigecycline in the interstitial fluid of wound margins versus that of uninfected thigh tissue in 8 adult diabetic patients intravenously (IV) administered 100 mg and then 50 mg of tigecycline twice daily for 3 to 5 doses. Prior to administration of the first dose, 2 microdialysis catheters were inserted into the subcutaneous tissue, the first within 10 cm of the wound margin and the second in the thigh of the same extremity. Samples for determination of plasma and tissue concentrations were simultaneously collected over 12 h under steady-state conditions. Tissue concentrations were corrected for percent in vivo recovery by the retrodialysis technique. Plasma samples were also collected for determination of protein binding at 1, 6, and 12 h postdose for each patient. Protein binding data were corrected using a fitted polynomial equation. The mean patient weight was 95.1 kg (range, 63.6 to 149.2 kg), the mean patient age was 63.5 +/- 9.4 years, and 75% of the patients were males. The mean values for the plasma, thigh, and wound free area under the concentration-time curve from 0 to 24 h (fAUC(0-24)) were 2.65 +/- 0.33, 2.52 +/- 1.15, and 2.60 +/- 1.02 mu g . h/ml, respectively. Protein binding was nonlinear, with the percentage of free drug increasing with decreasing serum concentrations. Exposure values for thigh tissue and wound tissue were similar (P = 0.986). Mean steady-state tissue concentrations for the thigh and wound were similar at 0.12 +/- 0.02 mu g/ml, and clearance from the tissues appeared similar to that from plasma. Tissue penetration ratios (tissue fAUC/plasma fAUC) were 99% in the thigh and 100% in the wound (P = 0.964). Tigecycline penetrated equally well into wound and uninfected tissue of the same extremity.