title: Slow release formulations of inhaled rifampin.
abstract: Rifampin microspheres were prepared by spray drying using either polylactic acid (PLA) or poly(lactic-co-glycolic acid) (PLGA) polymers in different drug to polymer ratios (90:10 to 5:95, w/w). The in-vitro release characteristics, particle-size distribution, and cytotoxicity (in an alveolar macrophage cell line) and pharmacokinetics in rats after pulmonary instillation were evaluated. Increasing the polymer content from 10% to 95% slowed down the in vitro drug release with PLGA particles showing a steeper change with increasing polymer content (100% to 20% drug release over 6 h) than PLA particles (88% to 42% drug release over 6 h). PLA microsphere formulations revealed lack of cytotoxicity and a mass median aerodynamic diameter (MMDA) of 2.22-2.86 mum, while PLGA particles were larger (MMDA of 4.67-5.11 mum). Pharmacokinetics differed among the formulations with the 10% PLA formulation showing a distinct sustained release (t (max) of 2 h vs 0.5 h of free drug) and a systemic bioavailability similar to that of free drug. Formulations with high polymer content showed a lower relative bioavailability (30%). This suggested that an optimal release rate existed for which a distinct amount of drug was delivered over an extended period of time.
authors.affiliation: Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, Florida, 32610, USA.
authors.forename: Intira
authors.initials: I
authors.lastname: Coowanitwong
authors.forename: Vikram
authors.initials: V
authors.lastname: Arya
authors.forename: Poj
authors.initials: P
authors.lastname: Kulvanich
authors.forename: Günther
authors.initials: G
authors.lastname: Hochhaus
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D000904:Antibiotics, Antitubercular / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood / Q000737:chemistry; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003692:Delayed-Action Preparations; D004337:Drug Carriers / Q000737:chemistry*; D004339:Drug Compounding; D016676:Macrophages, Alveolar / Q000187:drug effects; D008297:Male; D051379:Mice; D008863:Microspheres; D010316:Particle Size; D051381:Rats; D017207:Rats, Sprague-Dawley; D012293:Rifampin / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood / Q000737:chemistry; D012995:Solubility; D013499:Surface Properties
chemical_list: D000904:Antibiotics, Antitubercular; D003692:Delayed-Action Preparations; D004337:Drug Carriers; D012293:Rifampin