an antifolate drug used as salvage therapy for people with PCP who fail standard treatments. Trimetrexate can cause severe bone marrow toxicity, and is typically used in conjunction with leucovorin to protect against anemia.

A drug used for "salvage" therapy of pneumocystis carinii pneumonia, when other treatments have failed. Trimetrexate is enormously toxic unless administered with leucovorin, which "rescues" human cells from it's effects.