|Systematic (IUPAC) name|
|ATC code||P01 QP51|
|Mol. mass||340.42 g/mol|
|Half life||6.4-9.4 hours|
|Routes||IV, IM, inhalation|
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Pentamidine (formulated as a salt, pentamidine isethionate) 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).
Pentamidine is also used as a prophylactic against PCP in patients receiving chemotherapy, as they also have a depressed immune system as a direct side-effect of the drugs used. The mortality of untreated PCP is very high. Additionally, pentamidine has good clinical activity in treating leishmaniasis, and yeast infections caused by the organism Candida albicans. Pentamidine is also used as a prophylactic antibiotic for children undergoing treatment for leukemia.
The exact mechanism of its anti-protozoal action is unknown (though it may involve reactions with ubiquitin), despite the fact that it is a basic therapeutic modality (in concurrence with multiple antifungal medications) when treating Acanthamoeba infections in the immunocompromised patients. In the United States, pentamidine is currently designated an orphan drug by the U.S. Food and Drug Administration.
In the acute treatment of PCP, pentamidine is considered equally or slightly less active than co-trimoxazole (brand names Bactrim, Septrin, or Septra). Clinical evidence suggests that pentamidine is often better tolerated than co-trimoxazole because a high dose of co-trimoxazole is needed, which is associated with a high incidence and severity of side effects such as hepatitis, bone-marrow-damage, renal-damage, and life threatening skin disease (Lyell-syndrome). Moreover, many patients are or become allergic to co-trimoxazole. For treatment of PCP, 4 milligrams of pentamidine per kilogram of body weight is given intravenously once daily for 14 to 21 days. Treatment exceeding 21 days may be necessary, but is associated with increased toxicity. Intramuscular injection is not recommended. The effect of pentamidine often becomes evident within the first 2 days of treatment, with reduction in fever and improvement of respiratory function. In any case, improvements of chest x-ray studies occur within 6 to 8 days, provided therapy is successful. Pentamidine therapy cures 50 to 70% of all patients treated.
Primary prophylaxis of severely immunocompromised patients can be indicated where PCP has not yet been diagnosed. Secondary prophylaxis aims to prevent recurrent infections by PCP. For both forms of prophylaxis, an aerosolized formulation of pentamidine given by nebulizer once monthly in a dose of 300 mg is used. In primary prophylaxis, this reduces the long term likelihood of PCP by 70% when compared to no prophylaxis.
The mechanism is not well characterized, but there is some evidence that it may involve mitochondrial function.
Pentamidine can cause allergic and toxic side effects, which in part depend on the daily and/or cumulative dose:
The additional or sequential use of other nephrotoxic drugs like aminoglycosides, amphotericin B, capreomycin, colistin, polymyxin B, vancomycin, foscarnet, or cisplatin should be closely monitored, or whenever possible completely avoided.