Department of Clinical Pharmacology, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.
Department of Clinical Pharmacy, Institute of Pharmacy, University of Hamburg, Bundesstrasse 45, 20146, Hamburg, Germany.
J Antimicrob Chemother. 2021 Jul 15;76(8):2106-2113. doi: 10.1093/jac/dkab140.
The efficacy of an anti-infective drug is influenced by its protein binding (PB), since only the free fraction is active. We hypothesized that PB may vary in vitro and in vivo, and used clindamycin, a drug with high and concentration-dependent PB to investigate this hypothesis.
Six healthy volunteers received a single intravenous infusion of clindamycin 900 mg. Antibiotic plasma concentrations were obtained by blood sampling and unbound drug concentrations were determined by means of in vivo intravascular microdialysis (MD) or in vitro ultrafiltration (UF) for up to 8 h post dosing. Clindamycin was assayed in plasma and MD fluid using a validated HPLC-UV (ultraviolet) method. Non-linear mixed effects modelling in NONMEM® was used to quantify the PB in vivo and in vitro.
C max was 14.95, 3.39 and 2.32 mg/L and AUC0-8h was 41.78, 5.80 and 6.14 mg·h/L for plasma, ultrafiltrate and microdialysate, respectively. Calculated ratio of AUCunbound/AUCtotal showed values of 13.9%±1.8% and 14.7%±3.1% for UF and microdialysate, respectively. Modelling confirmed non-linear, saturable PB for clindamycin with slightly different median (95% CI) dissociation constants (Kd) for the alpha-1 acid glycoprotein (AAG)-clindamycin complex of 1.16 mg/L (0.91-1.37) in vitro versus 0.85 mg/L (0.58-1.01) in vivo. Moreover, the estimated number of binding sites per AAG molecule was 2.07 (1.79-2.25) in vitro versus 1.66 in vivo (1.41-1.79).
Concentration-dependent PB was observed for both investigated methods with slightly lower levels of unbound drug fractions in vitro as compared with in vivo.
抗感染药物的疗效受其蛋白结合率（PB）的影响，因为只有游离部分具有活性。我们假设 PB 可能在体外和体内发生变化，并用克林霉素（一种具有高浓度依赖性 PB 的药物）来验证这一假设。
6 名健康志愿者单次静脉输注克林霉素 900mg。通过采血获得抗生素血浆浓度，并通过体内血管内微透析（MD）或体外超滤（UF）在给药后 8 小时内测定未结合药物浓度。使用经验证的 HPLC-UV（紫外线）方法在血浆和 MD 液中检测克林霉素。NONMEM®中的非线性混合效应模型用于定量体内和体外的 PB。
C max 分别为 14.95、3.39 和 2.32mg/L，AUC0-8h 分别为 41.78、5.80 和 6.14mg·h/L，分别为血浆、超滤液和微透析液。计算的游离 AUC/总 AUC 比值分别为 UF 和微透析液的 13.9%±1.8%和 14.7%±3.1%。模型证实克林霉素的 PB 呈非线性、饱和性，α-1 酸性糖蛋白（AAG）-克林霉素复合物的体外和体内解离常数（Kd）分别为 1.16mg/L（0.91-1.37）和 0.85mg/L（0.58-1.01）。此外，每个 AAG 分子的结合位点估计数分别为 2.07（1.79-2.25）和 1.66（1.41-1.79）。
两种方法均观察到浓度依赖性 PB，与体内相比，体外未结合药物分数略低。
