In the treatment of infectious diseases with drugs of the sulfonamide group it is desirable to maintain an optimum concentration of these drugs in the blood, and therefore periodic tests are essential for best results. The method herein described is simple and accurate and can be performed in a few minutes at the bedside or in the office. It is a modification of the Marshall method, but it has the following advantages: All reagents are stable, in tablet form. No pipets are required except one for collecting blood. Only 0.1 cc. of blood for sulfanilamide and 0.2 cc. of blood for sulfapyridine and sulfathiazole are required. The blood can either be oxalated or be obtained from the finger tip or the ear lobe.
A special colorimeter has been developed for this test which is small, compact and accurate and can be carried in a bag or in a pocket. It