Kroll M H, Jackson A J, Elin R J
Clin Chem. 1987 Jul;33(7):1219-22.
Cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids. The apparent concentration of hormone is increased from three- to 10-fold in samples from patients receiving cefoxitin when the Amberlite XAD-2 "Clini-Skreen" column is used. To determine the mechanism of interference, we reacted aqueous solutions of cefoxitin, cortisol, cortisone, and 11-deoxycortisol with phenylhydrazine; recorded the adsorption spectra; and determined the molar absorptivities and the equilibrium and rate constants. Also, we recorded the absorption spectra of phenylhydrazine with eight other cepha antibiotics and benzylpenicillin. Cortisol, cortisone, 11-deoxycortisol, and cefoxitin react with phenylhydrazine and absorb light with superimposable spectra and absorption maxima of 410 nm. The other antibiotics react with phenylhydrazine but absorbance maxima of the products vary, none being at 410 nm. Cortisol, cortisone, and 11-deoxycortisol react with phenylhydrazine 35-fold faster, have equilibrium constants ninefold greater, and have molar absorptivities 1.6 times that of cefoxitin. Thus, cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids by forming a chromophore with the same absorbance maximum and with a molar absorptivity similar to cortisol, but much more slowly.
头孢西丁会干扰尿17-羟皮质类固醇的测定。当使用Amberlite XAD - 2“临床筛查”柱时，接受头孢西丁治疗的患者样本中激素的表观浓度会增加3至10倍。为了确定干扰机制，我们使头孢西丁、皮质醇、可的松和11-脱氧皮质醇的水溶液与苯肼反应；记录吸附光谱；并测定摩尔吸光系数以及平衡常数和速率常数。此外，我们记录了苯肼与其他八种头孢菌素抗生素和苄青霉素的吸收光谱。皮质醇、可的松、11-脱氧皮质醇和头孢西丁与苯肼反应，吸收具有叠加光谱且最大吸收波长为410nm的光。其他抗生素与苯肼反应，但产物的最大吸光度各不相同，均不在410nm处。皮质醇、可的松和11-脱氧皮质醇与苯肼的反应速度快35倍，平衡常数大9倍，摩尔吸光系数是头孢西丁的1.6倍。因此，头孢西丁通过形成一种具有与皮质醇相同最大吸光度且摩尔吸光系数相似但反应慢得多的发色团来干扰尿17-羟皮质类固醇的测定。
