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Nebupent (Pentamidine Isethionate) - Description and Clinical Pharmacology

 
 



For Oral Inhalation Only

DESCRIPTION

NebuPent (pentamidine isethionate), an antifungal agent, is a nonpyrogenic lyophilized product. After reconstitution with Sterile Water for Injection, USP, NebuPent is administered by inhalation via the Respirgard® II nebulizer [Marquest, Englewood, CO] (see DOSAGE AND ADMINISTRATION ).

Pentamidine isethionate, 4,4’-[1,5-pentane-diylbis(oxy)]bis-benzenecarboximidamid, is a white crystalline powder soluble in water and glycerin and insoluble in ether, acetone, and chloroform.


C19H24N4O2•2C2H6O4S                            592.68

Each vial contains 300 mg pentamidine isethionate.

CLINICAL PHARMACOLOGY

Microbiology

Mechanism of Action

Studies suggest that the pentamidine isethionate interferes with microbial nuclear metabolism by inhibition of DNA, RNA, phospholipid and protein synthesis.  However, the mode of action is not fully understood.

Activity in vitro and in vivo

Pentamidine isethionate, an aromatic diamidine, is known to have activity against Pneumocystis jiroveci.

Pharmacokinetics

In 5 AIDS patients with suspected Pneumocystis jiroveci pneumonia (PJP), the mean concentrations of pentamidine determined 18 to 24 hours after inhalation therapy were 23.2 ng/mL (range 5.1 to 43.0 ng/mL) in bronchoalveolar lavage fluid and 705 ng/mL (range 140 to 1336 ng/mL) in sediment after administration of a 300 mg single dose via the Respirgard® II nebulizer. In 3 AIDS patients with suspected PJP, the mean concentrations of pentamidine determined 18 to 24 hours after a 4 mg/kg intravenous dose were 2.6 ng/mL (range 1.5 to 4.0 ng/mL) in bronchoalveolar lavage fluid and 9.3 ng/mL (range 6.9 to 12.8 ng/mL) in sediment. In the patients who received aerosolized pentamidine, the peak plasma levels of pentamidine were at or below the lower limit of detection of the assay (2.3 ng/mL).

Following a single 2-hour intravenous infusion of 4 mg/kg of pentamidine isethionate to 6 AIDS patients, the mean plasma Cmax, T 1/2 and clearance were 612 ± 371 ng/mL, 6.4 ± 1.3 hr and 248 ± 91 L/hr respectively. In another study of aerosolized pentamidine in 13 AIDS patients with acute PJP who received 4 mg/kg/day administered via the Ultra Vent® jet nebulizer, peak plasma levels of pentamidine averaged 18.8 ± 11.9 ng/mL after the first dose. During the next 14 days of repeated dosing, the highest observed Cmax averaged 20.5 ± 21.2 ng/mL. In a third study, following daily administration of 600 mg of inhaled pentamidine isethionate with the Respirgard® II nebulizer for 21 days in 11 patients with acute PJP, mean plasma levels measured shortly after the 21st dose averaged 11.8 ± 10.0 ng/mL. Plasma concentrations after aerosol administration are substantially lower than those observed after a comparable intravenous dose. The extent of pentamidine accumulation and distribution following chronic inhalation therapy are not known.

In rats, intravenous administration of a 5 mg/kg dose resulted in concentrations of pentamidine in the liver and kidney that were 87.5 and 62.3-fold higher, respectively, than levels in those organs following 5 mg/kg administered as an aerosol.

No pharmacokinetic data are available following aerosol administration of pentamidine in humans with impaired hepatic or renal function.

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