Trimethoprim-Sulfamethoxazole The concomitant use of d,l -leucovorin with trimethoprim-sulfamethoxazole for the acute treatment of Pneumocystis jiroveci pneumonia in patients with HIV infection was associated with increased rates of treatment failure and morbidity in a placebo-controlled study [see Warnings and Precautions ( 5.3 )] .
Source: FDA drug label - levoleucovorin injection