Quantification of Ceftazidime in the Vitreous Humor Using Ultra-performance Convergence Chromatography-Tandem Mass Spectrometry.

BACKGROUND

Patients with suspected postoperative bacterial endophthalmitis are at a high risk of vision loss if not treated immediately and adequately. Initial treatment typically involves the intravitreal administration of antibiotics, with ceftazidime in combination with vancomycin being the common agents administered. Unbound ceftazidime exposure should exceed the minimum inhibitory concentration at the infection site. To facilitate investigation of the disposition of ceftazidime after its intravitreal injection, an ultra-performance convergence chromatography-tandem mass spectrometry method for quantifying ceftazidime in the vitreous humor was developed and validated in this study.

METHODS

Each sample (20 µL) was prepared by protein precipitation of the test sample mixed with the internal standard solution (2 mg/L meropenem-d 6 in methanol). The sample was analyzed using a Waters Acquity UPC 2 system coupled to a Waters Xevo TQ-S micro triple quadrupole mass spectrometer (Waters Corp, Milford, MA). The method was validated according to guidelines published by the European Medicines Agency and US Food and Drug Administration. The validation parameters were linearity, limits of quantification (LOQs), accuracy, interday and intraday precision, carryover effect, autosampler stability, and short-term and long-term stability.

RESULTS

The method had a linear range ( r2 > 0.990) between 1.3 and 99.6 mg/L and exhibited less than 15% inaccuracy and imprecision. The carryover effect was significant (53% of the lower LOQ) when injecting a blank sample after an upper LOQ sample but was negated after injecting an additional blank sample. Therefore, 1 blank sample should be injected after each patient sample.

CONCLUSIONS

This ultra-performance convergence chromatography-tandem mass spectrometry method facilitates the rapid and reliable determination of ceftazidime in the vitreous humor, with a short run time of 5 minutes. It was successfully applied to 72 clinical samples.