Coadministration has not been studied. Sulfadiazine has been associated with crystalluria leading to renal toxicity and in some cases renal failure, and case reports in immunocompromised patients have suggested that AIDS patients may be particularly prone to sulfadiazine-induced renal toxicity. As emtricitabine is predominantly excreted via active renal transport, monitoring of renal function is warranted if sulfadiazine is administered with emtricitabine.