PHARMACOLOGICAL STUDIES ON SULFAQUINOXALINE

¹ From the Merck Institute for Therapeutic Research, Rahway, New Jersey

Sulfaquinoxaline is as effective against certain species of avian malaria as sulfadiazine and sulfapyrazine on the basis of blood concentrations and is approximately twice as active when comparison is made on the basis of weight dosage. The drug is remarkable in that it remains in the blood for days whether given by mouth or intravenously.

Sulfaquinoxaline is unique among the sulfonamides reported in the literature in that it is capable of producing a marked hypoprothrombinemia within 24 hours in rats and dogs on a normal diet. In the rat and the dog the effect of the drug on the prothrombin time can be prevented by the simultaneous administration of vitamin K₁.

In the rat and the monkey kidney damage occurs when the plasma concentration reaches 10 mgm. % or higher. The distal convoluted tubules and the collecting tubules are blocked by crystals of the relatively insoluble 3-hydroxy derivative. The maintenance of a urine pH of 8.5 or above in the rat by the oral administration of sodium bicarbonate does not prevent the precipitation. Nephrolithiasis has not been observed in the dog or the rabbit.