Pentamidine dihydrochloride is primarily used as an antimicrobial agent, particularly in the treatment of parasitic infections. It is highly effective against Pneumocystis pneumonia (PCP), a serious infection often seen in immunocompromised patients, such as those with HIV/AIDS. The drug is administered via inhalation or intravenous injection, depending on the severity and type of infection.

In addition to its use in treating PCP, pentamidine dihydrochloride is also employed in the management of other parasitic diseases, such as leishmaniasis and African trypanosomiasis (sleeping sickness). For leishmaniasis, it is particularly useful in cases where other treatments, like antimonials, are ineffective or contraindicated.

The drug works by interfering with the DNA and RNA synthesis of the parasites, leading to their destruction. However, its use requires careful monitoring due to potential side effects, including kidney toxicity, low blood pressure, and blood sugar irregularities. Despite these risks, pentamidine dihydrochloride remains a critical component in the treatment of specific life-threatening infections.