Pentamidine

Pentamidine isethionate is an antiparasitic and antimicrobial medication in the diamidine class. It is used to treat Pneumocystis jirovecii pneumonia (PCP) and to prevent PCP in people who cannot tolerate first‑line therapies, as well as to treat or attempt treatment of certain protozoal infections.

Medical uses include the systemic treatment of PCP in patients with sulfa intolerance or allergy to trimethoprim-sulfamethoxazole, and prevention of PCP in high‑risk individuals. It is also used for early-stage human African trypanosomiasis (sleeping sickness) due to Trypanosoma brucei gambiense, and has been employed as an alternative therapy for visceral leishmaniasis in some settings.

Administration typically occurs by injection (intravenous or intramuscular). An inhaled form (pentamidine isethionate for inhalation) is available for PCP prophylaxis and is designed to reduce systemic toxicity. Dosing regimens vary by indication and formulation, and treatment often requires monitoring for adverse effects.

The mechanism of action is not completely understood, but pentamidine is thought to bind preferentially to DNA and disrupt nucleic acid synthesis and mitochondrial function in susceptible organisms, contributing to its antiparasitic effects.

Pharmacokinetics: pentamidine has poor oral bioavailability and is given by parenteral routes for systemic infections. It distributes broadly in body tissues and is excreted by the kidneys and liver to varying extents. The inhaled form results in more localized exposure with less systemic uptake.

Adverse effects can be significant and include nephrotoxicity, hypoglycemia or hyperglycemia, hypotension, pancreatitis, electrolyte disturbances, and infusion reactions. Cardiac or bronchospastic responses may occur with certain routes of administration, and care is required in patients with kidney disease, diabetes, or electrolyte abnormalities.