Miniaturized Microbiological Method to Determine the Potency of Rifaximin in Tablets

Rifaximin, a semi-synthetic antimicrobial, does not present microbiological method described in official compendia, and there is a lack of literature on this topic. The quality control of antimicrobials is extremely important to evaluate the real potency of pharmaceutical products.

A miniaturized turbidimetric method for determining the potency of rifaximin in tablets was developed and validated by turbidimetry, according to the international guidelines.

Escherichia coli ATCC 10536 IAL 2393, brain heart infusion (BHI) broth, inoculum at 8%, rifaximin in purified water with 20% ethanol at 5, 10, and 20 μg/mL and 530 nm were used.

The method was considered selective for rifaximin, as the adjuvants did not show activity; linear with correlation coefficients 0.9998 for standard and 0.9999 for sample; accurate with 99.73% recovery; precise with RSD less than 3%; and robust in the face of small variations in (i) rifaximin volume, (ii) proportion of ethanol, (iii) inoculum volume.

The method is considered adequate and safe to evaluate the potency of rifaximin in tablets, contemplating speed, low cost, low waste generation, and ease of operation.

This work usescurrent, sustainable, and green analytical chemistry and can be used in the routine analyses of rifaximin by laboratories and the pharmaceutical industry around the world.