ABSTRACT
A novel inhalable rifapentine dry powder formulation could improve pulmonary rifapentine concentrations resulting in a significantly shorter time to treat tuberculosis infection. The pharmacokinetics of rifapentine (20mg/kg) in healthy mice was compared following intratracheal (IT) and intraperitoneal (IP) administration. Plasma, bronchoalveolar lavage (BAL) and tissue samples were collected and drug levels were quantified at time points up to 24h. Concentration-time data were analysed using a mixed-effects modelling approach to provide model-based estimates of area under the concentration-time curve from time 0 to infinity (AUC0-∞). IT delivery had considerably higher peak rifapentine lung and BAL concentrations and associated AUC0-∞ compared with IP delivery. The plasma AUC0-∞ following IT dry powder delivery was ca. four-fold smaller than the value for IP delivery. Inhaled delivery of rifapentine has the potential to selectively enhance therapeutic efficacy at the pulmonary site of infection whilst minimising systemic exposure and related toxicity.
Subject(s)
Antibiotics, Antitubercular/administration & dosage , Antibiotics, Antitubercular/pharmacokinetics , Rifampin/analogs & derivatives , Administration, Inhalation , Aerosols/administration & dosage , Animals , Bronchoalveolar Lavage Fluid/chemistry , Female , Lung/chemistry , Mice, Inbred BALB C , Models, Animal , Models, Statistical , Plasma/chemistry , Powders/administration & dosage , Rifampin/administration & dosage , Rifampin/pharmacokineticsABSTRACT
Recent murine studies found that rifapentine, dosed daily, at least halved tuberculosis treatment times compared with standard rifampicin and isoniazid-containing regimens. However, in humans, an inhalable form of rifapentine may be necessary to considerably shorten treatment duration because of the physiological barriers associated with oral therapy. The current study compares two inhalable rifapentine dry powders-a novel pure crystalline form and an amorphous form-by a series of in vitro tests. The crystalline and amorphous powders had a mass median aerodynamic size of 1.68 ± 0.03 and 1.92 ± 0.01 µm, respectively, associated with a fine particle fraction of 83.2 ± 1.2% and 68.8 ± 2.1%, respectively. A quinone degradation product was identified in the amorphous powder stored for 1 month, whereas the crystalline form remained chemically stable after storage at both 0% and 60% relative humidity, 25°C, for at least 3 months. Solubilized rifapentine was well tolerated by pulmonary tissue and macrophage cells up to approximately 50 µM. The accumulation of rifapentine within alveolar macrophage cells was significantly higher than for rifampicin, indicating enhanced delivery to infected macrophages. The novel inhalable crystalline form of rifapentine is suitable for targeted treatment of tuberculosis infection and may radically shorten treatment duration.
