Yoshifumi Wakiya

Variability in teicoplanin protein binding and its prediction using serum albumin concentrations

The impact of lower serum albumin levels on teicoplanin pharmacokinetics has not been previously determined. The authors assessed the relationship between total and free concentrations of teicoplanin in serum samples obtained from patients receiving teicoplanin therapy for Gram-positive bacterial infections. In addition, the authors determined the contribution of serum albumin concentrations to the unbound fraction of teicoplanin. One hundred ninety-eight serum samples were obtained from 65 patients undergoing routine therapeutic drug monitoring of teicoplanin. Free serum teicoplanin was separated by ultrafiltration, and total and free serum concentrations of teicoplanin were determined by a fluorescence polarization immunoassay. Regression analysis was then performed to build a prediction model for the free serum teicoplanin concentration from the total serum teicoplanin concentration and the serum albumin level using the first 132 samples. The predictive performance of this model was then tested using the next 66 samples. Free serum teicoplanin concentrations (Cf) (μg/mL) were predicted using a simple model constructed using total serum teicoplanin (Ct) (μg/mL) and albumin concentrations (ALB) (g/dL): Cf = Ct/(1 + 1.78 * ALB). This model could estimate free serum teicoplanin concentrations with a small bias and an acceptable error. The measured free level of teicoplanin will lie between 0.63 and 1.38 times the predicted concentration in 95% of cases. Serum albumin level plays a major role in the variability of the fraction unbound of teicoplanin. This model can reliably estimate free serum teicoplanin concentrations more easily than by using direct measurements.

Clinical Evaluation of Early Post-Marketing Phase Vigilance-Features of Adverse Events Noted in Early Post-marketing Phase Vigilance-

We examined differences in adverse drug reactions reported in trials for new drug applications and those reported in early post-marketing phase vigilance (EPPV) for drugs approved between October, 2001 and July, 2003. In EPPV reports, we found that the proportion of adverse drug reactions noted from blood tests (e.g. drug-induced hepatitis, hematology adverse reactions, electrolyte metabolism disorders, and renal dysfunction) was less than that of other adverse drug reactions. We consider that this was because blood tests were not conducted regularly enough and the reason that such reactions are severe when discovered.Since EPPV is considered as phase IV of drug testing, regular blood tests are still required and we feel that it is necessary to carry out pharmacovigilance more thoroughly to ensure the safety of drugs after they have been marketed.