Pentamidine isethionate in the treatment of Pneumocystis carinii pneumonia.

The chemistry, antiprotozoal activity, pharmacology, clinical efficacy, adverse effects, dosage, administration, and hospital formulary considerations of pentamidine isethionate are reviewed. Pentamidine, an aromatic diamidine, has been used since the 1940s to treat a variety of protozoal infections. It is now most commonly administered in the treatment of Pneumocystis carinii pneumonia (PCP). It is generally not metabolized, and it is stored or bound to tissue and excreted slowly as the parent compound. Pentamidine is clearly effective in the treatment of PCP; however, the high incidence of adverse reactions associated with the drug led to the use of trimethoprim-sulfamethoxazole (TMP-SMX) as the first-line agent for PCP. Recent studies have reported a high incidence of adverse reactions, including leukopenia and hepatotoxicity, associated with the use of TMP-SMX therapy for PCP in patients with the acquired immunodeficiency syndrome (AIDS). The severity and frequency of these reactions suggest a possible new role for pentamidine in patients with AIDS who have PCP. The recommended intramuscular and intravenous dosage of pentamidine isethionate for adults and children is 4 mg/kg/day for 14 days. Intramuscular administration is recommended; however, intravenous administration is a safe alternative if the dose is infused over a 60-minute period. Pentamidine isethionate has specific application in the treatment of PCP as a second-line agent reserved for patients who cannot tolerate TMP-SMX.