A 32-year-old male was on sulfadiazine for toxoplasmosis therapy. The patient wa

Question

A 32-year-old male was on sulfadiazine for toxoplasmosis therapy. The patient was receiving 2 g of sulfadiazine four times a day for two weeks. The patient developed dysuria and problems voiding, including the presence of red urine, red stones, and severe urethral pain. The pH of the urine was found to be acidic (5.5). Based on your knowledge of ionic equilibriums and the pKa of this weakly acidic drug (6.48), describe the cause of this clinical situation and suggest possible remedies for this patient.

Explanation / Answer

As the patient is given sulfadiazine, which is a sulfonamide used for the treatment of toxoplasmosis. Its primary metabolites include acetylated 2-sulfanilamidopyrimidine, a poorly soluble weak acid that may crystallize in urine. High-dose sulfadiazine induces crystalluria in 40% of patients. The crystal deposition is enhanced by dehydration, hypoalbuminemia, chronic kidney disease, inadequate high doses, acidic urinary pH (<5.5), and there is presence of blood in urine and stools. Therefore, treatment involves cessation of the sulfadiazine with possible switching to a trimethoprim–sulfamethoxazole regimen, aggressive volume repletion, and urine alkalization at pH of >7.15.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.