A Microtiter Plate Assay for Sulfonamides

Abstract
Sulfamethoxazole, sulfisoxazole, and sulfadiazine are sulfonamides used in the treatment of several infectious diseases. Several studies have demonstrated that the amino substituent plays an important role in both the toxicity and the therapeutic effect of these drugs. In view of these findings, a rapid and convenient method of analysis would be useful for monitoring selected patients receiving these drugs. With the increasing use of microtiter plate methodology in the clinical laboratory, an assay based upon the Bratton-Marshall reaction with the amino substituent was adapted to the microtiter plate format. The results indicate that the microtiter plate assay for sulfonamides retains the sensitivity and linearity necessary for analysis of sulfonamides in biological fluids at clinically relevant concentrations. The assay is simple, rapid, convenient, and suitable for monitoring procedures where only the measurement of the active drug concentration is required.