Kwok Alvin K H, Hui Mamie, Pang Chi Pui, Chan Raphael C Y, Cheung Siu Wai, Yip Cynthia M S, Lam Dennis S C, Cheng Augustine F B
Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong, China.
Invest Ophthalmol Vis Sci. 2002 Apr;43(4):1182-8.
To investigate the precipitation process of a mixture of vancomycin and ceftazidime by equilibrium dialysis and determine its subsequent effect on the level of free antibiotics for treatment of endophthalmitis.
Concentrations of vancomycin and ceftazidime in an equilibrium dialysis chamber were measured during the equilibrium process by high-performance liquid chromatography. Normal saline (NS), balanced salt solution (BSS), and vitreous were used separately as the medium of dialysis.
Precipitation of ceftazidime occurred at 37 degrees C but not at room temperature and did not affect the pH of the medium. It formed precipitate on its own or when mixed with vancomycin in all the three media of NS, BSS, and vitreous. More precipitation was formed if ceftazidime was initially prepared in BSS than in NS. After 168 hours in the dialysis chambers, ceftazidime prepared in NS precipitated to 54% of that in vitreous, compared with 88% if prepared in BSS. At 48 hours, ceftazidime prepared in NS decreased from an initial concentration of 137.5 to 73.4 microg/mL in vitreous medium and to 6.3 microg/mL if prepared in BSS. Precipitation of vancomycin was negligible.
Based on this in vitro investigation, ceftazidime precipitates in vitreous at body temperature, regardless of the presence of vancomycin. NS is preferred to BSS as a preparation medium for antibiotics for intravitreal injection, because the extent of ceftazidime precipitation is less. However, due to precipitation, the concentration of free ceftazidime in vitreous may not be sufficiently high for antibacterial activity against most common organisms.
通过平衡透析研究万古霉素和头孢他啶混合物的沉淀过程，并确定其对治疗眼内炎时游离抗生素水平的后续影响。
在平衡过程中，采用高效液相色谱法测定平衡透析室内万古霉素和头孢他啶的浓度。分别使用生理盐水（NS）、平衡盐溶液（BSS）和玻璃体作为透析介质。
头孢他啶在37℃时发生沉淀，而在室温下不沉淀，且不影响介质的pH值。在NS、BSS和玻璃体这三种介质中，头孢他啶自身或与万古霉素混合时均会形成沉淀。如果头孢他啶最初在BSS中配制，则比在NS中形成的沉淀更多。在透析室中放置168小时后，NS中配制的头孢他啶沉淀至玻璃体中沉淀量的54%，而在BSS中配制时则为88%。在48小时时，NS中配制的头孢他啶在玻璃体介质中从初始浓度137.5微克/毫升降至73.4微克/毫升，在BSS中配制时则降至6.3微克/毫升。万古霉素的沉淀可忽略不计。
基于这项体外研究，无论是否存在万古霉素，头孢他啶在体温下都会在玻璃体中沉淀。作为玻璃体内注射抗生素的配制介质，NS比BSS更可取，因为头孢他啶的沉淀程度较小。然而，由于沉淀作用，玻璃体中游离头孢他啶的浓度可能不足以对大多数常见病原体产生抗菌活性。
