Teicoplanin A2-3

The interaction between the main components of the new glycopeptide antibiotic teicoplanin, A2-2, A2-3, A2-4, A2-5 and A3-1, and human serum albumin has been studied in vitro by equilibrium dialysis (pH 7.4, 37 degrees C). From Scatchard analysis of the data, the calculated association constants (Ka) were: A2-2, 2.47 X 10(4), A2-3, 2.86 X 10(4), A2-4, 2.95 X 10(4) and A2-5, 3.87 X 10(4) mol.l-1. The number of binding sites per albumin molecule ranged between 1.23 to 1.31. A3-1 had a lower affinity with a Ka of about 5 X 10(3) mol.l-1. Extrapolated to the in vivo situation, the data suggested that about 90-95% of A2 components will be bound to serum albumin, and about 68-72% of A3-1. The in vitro findings were confirmed by a pharmacokinetic study in volunteers given [14C] teicoplanin i.v., in whom the fraction of teicoplanin bound to serum protein ranged between 87.6 and 90.8%.

Teicoplanin is a new antibiotic consisting of closely related glycopeptides. Following an iv bolus of 400 mg teicoplanin, the pharmacokinetics of the individual components A3-1, A2-1, A2-2, A2-3, A2-4, and A2-5 was studied in five healthy volunteers by HPLC. For each subject, plasma and urine data of the individual components were simultaneously fitted by a triexponential disposition model. No significant differences were observed between the components of the A2 group in the initial volume of distribution, 0.05-0.06 L/kg, and the half-life of the second disposition phase, 2.5-3.0 hr. Significant differences were found in the volume of distribution at steady state (Vss 0.42-0.92 L/kg), the half-lives of the first (0.18-0.26 hr) and the third (48.1-66.8 hr) disposition phases, the total clearance (CL 5.4-19.3 ml/hr per kg), the renal clearance (CLR 2.8-16.1 ml/hr per kg), and the percentage of the administered dose excreted in urine (Ae 53-85%). A highly significant correlation was found between the lipophilicity of the individual components increasing from A2-1 to A2-5, and the values of the kinetic parameters. As the lipophilicity increases the fraction unbound in plasma, Vss, CL, CLR, and Ae decrease, whereas the unbound steady state volume of distribution and the unbound nonrenal clearance increase. A modest degree of accumulation of each teicoplanin component in plasma is predicted to occur at steady state following repeated administration of teicoplanin given daily, with accumulation slightly higher for the more lipophilic components A2-4 and A2-5.

A direct injection-based, simple, accurate, and robust LC-MS/MS method was developed and validated for the determination of teicoplanin in human plasma. Patient plasma samples were diluted in an aqueous buffer prior to injection into the LC-MS/MS system. Chromatographic separation was achieved using a Cadenza HS-C18 column and a gradient mixture of acetonitrile-water (both containing 0.1% formic acid) as the mobile phase at a flow rate of 0.5mL/min. The analytes were detected in multiple reaction monitoring mode with positive ion electrospray ionization. The concentration of teicoplanin was determined as the sum of six components (A3-1, A2-1, A2-2, A2-3, A2-4, and A2-5). The calibration curve was linear over a concentration range of 1-50mg/L, which covered the clinically accepted trough and therapeutic plasma levels. The intra- and inter-day precision and accuracy values were both less than 15%. This validated method was successfully applied to therapeutic drug monitoring of teicoplanin in routine clinical practice. Thus, we expect it to be useful for the determination of teicoplanin concentration in human plasma.