Caspofungin is an echinocandin antifungal used in the treatment of invasive fungal infections. Several methods have been reported for the quantitative analysis of echinocandins; however, there is no microbiological assay for determination of caspofungin potency in the presence of its degradation products. This study aimed to develop and validate a microbiological method for quantitative analysis of caspofungin in lyophilized powder, evaluate the stability, and determinate the degradation kinetics of the drug when the finished product is submitted to heat stress. A procedure was established to estimate measurement uncertainty for routine analysis. The validation was performed as recommended in the current official guidelines. The agar diffusion method is based on the inhibitory effect of caspofungin on Candida albicans. Results showed selectivity, linearity, precision, and accuracy of the method. Statistical analysis demonstrated that method is linear (in the range 2.5 to 16 microg/mL, y= 15.73 + 6.4x, r2 = 0.9965), precise (intermediate precision: 2.54%), and accurate (recovery range: 95.01-102.46%). The proposed method allowed evaluation of the thermal stability of the drug at 80 degreesC for 120 min and determination of first order degradation kinetics. The variability of inhibition zone sizes was the most important source of uncertainty at about 87% of the overall uncertainty (103.0+/-1.7%). These results show that the proposed method is applicable to routine laboratory testing, and is sensitive to thermal degradation of caspofungin.

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Okamoto, R. T. Development of rapid analytical method of cephalexin in oral suspension powder by infrared spectroscopy. 140 p. Thesis

The aim of this work is to develop and validate a microbiological assay for ceftriaxone with a view to the employment of this method to assess photo-stability in commercial products. The experimental conditions included: (1) ceftriaxone standard solution in concentrations of 2.6 µg/mL, 3.2 µg/mL, 4.0 µg/mL, 5.0 µg/mL and 6.3 µg/mL, using phosphate buffer pH 6.0 as diluent, (2) Petri dishes prepared by adding 21-mL of antibiotic medium as base layer and 4-mL of the same medium, inoculated with Bacillus subtilis (ATCC 6633) in a proportion of 0.5% and (3) incubation at 37ºC for 18 hours. The method showed specificity, good linearity in the range from 2.6 to 6.3 µg/mL, as well as good precision (RSD repeatability of 1.7% and RSD intermediate precision of 2.2%) and accuracy (recovery of 101.1%). Commercial samples of ceftriaxone were exposed to light in their primary and secondary packing, being afterwards directly exposed to light. The potencies of commercial samples were then determined by the developed and validated microbiological assay.The results indicate that primary and secondary packing provide satisfactory protection of ceftriaxone from light.