title: In vitro characterization studies of self-microemulsified bosentan systems.
abstract: BACKGROUND
  Bosentan is a poorly soluble drug and pose challenges in designing of drug delivery systems.
  
  
  OBJECTIVE
  The objective of this study is to enhance the solubility, dissolution and shelf-life of bosentan by formulating it as S-SMEDDS capsules.
  
  
  METHODS
  Solubility of bosentan was tested in various liquid vehicles such as oils (rice bran and sunflower), surfactants (span 20 and tween 80) and co-surfactants (PEG 400 and propylene glycol) and microemulsions were developed. Bosentan was incorporated into appropriate microemulsion systems which were previously identified from pseudo ternary phase diagrams. Bosentan-loaded SMEDDS were evaluated for drug content, drug release, zeta potential, and droplet size. The selected liquid SMEDDS were converted into solid SMEDDS by employing adsorption and melt granulation. Solid SMEDDS were characterized for micromeritics and evaluated for drug content, drug release, and shelf-life.
  
  
  RESULTS
  Isotropic systems R5, R13, S5, and S13 with submicron droplet size had exhibited 85.45, 94.12, 81.67, and 96.64% drug release, respectively. Solid SMEDDS of MR13 and AS13 formulations with rapid reconstitution ability, exhibited 84.85 and 86.74% of on par drug release. The formulations were physicochemically intact for 1.02 and 1.56 years.
  
  
  CONCLUSIONS
  Liquid SMEDDS composed with PEG400 had displayed optimal characters. Solid SMEDDS had high-dissolution profiles than bosentan due to modification in the crystalline structure of drug upon microemulsification.
  
  
  CONCLUSIONS
  Thus, solid SMEDDS addressed the solubility, dissolution, and stability issues of bosentan and becomes an alternate for clinical convenience.
authors.affiliation: a Department of Pharmaceutics, Centre for Research Studies , Krishna University , Machilipatnam , India.|b Department of Pharmaceutics , PES College of Pharmacy , Bangalore , India.
authors.forename: Harini Chowdary
authors.initials: HC
authors.lastname: Vadlamudi
authors.affiliation: c Division of Pharmaceutics , Sri Padmavathi School of Pharmacy , Tirupati , India.
authors.forename: Prasanna Raju
authors.initials: PR
authors.lastname: Yalavarthi
authors.affiliation: d Department of Chemistry , Krishna University , Machilipatnam , India.
authors.forename: Basaveswara Rao
authors.initials: BR
authors.lastname: M V
authors.affiliation: e Department of Chemistry , Al-Shifa College of Pharmacy , Poonthavanam , India.
authors.forename: Arun
authors.initials: A
authors.lastname: Rasheed
authors.affiliation: c Division of Pharmaceutics , Sri Padmavathi School of Pharmacy , Tirupati , India.
authors.forename: Tejeswari
authors.initials: T
authors.lastname: N
mesh_terms: D000959:Antihypertensive Agents / Q000008:administration & dosage*; D000077300:Bosentan; D002214:Capsules; D004339:Drug Compounding; D016503:Drug Delivery Systems; D004355:Drug Stability; D004655:Emulsions; D010938:Plant Oils / Q000737:chemistry; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013449:Sulfonamides / Q000008:administration & dosage*; D014783:Viscosity
chemical_list: D000959:Antihypertensive Agents; D002214:Capsules; D004655:Emulsions; D010938:Plant Oils; D013449:Sulfonamides; D000077300:Bosentan
keywords: Phase diagram; bioavailability; endothelin; microemulsion; zeta potential