Pentamidine (formulated as a salt, pentamidine diisethionate or dimesilate) is an antimicrobial medication given for prevention and treatment of pneumocystis pneumonia (PCP) caused by Pneumocystis jirovecii (formerly known as Pneumocystis carinii), a severe interstitial type of pneumonia often seen in patients with HIV infection. The drug is also the mainstay of treatment for stage I infection with Trypanosoma brucei gambiense (West African trypanosomiasis).