rifampin and ethyl-cellulose

Topics: Antibiotics, Antitubercular; Calorimetry, Differential Scanning; Cellulose; Chemical Precipitation; Dimethyl Sulfoxide; Drug Compounding; Drug Liberation; Microscopy, Electron, Scanning; Particle Size; Rifampin; Solvents; Spectroscopy, Fourier Transform Infrared; X-Ray Diffraction

The rifampicin release studies from ethylcellulose coated nonpareil beads were studied. Propylene glycol and Castor oil were used as plasticizers. The in vitro dissolution studies revealed that the release rate is inversely proportional to percent of coating thickness. The release rate also depends on the type of plasticizer used in the coating polymer. The mechanism of drug release follows Higuchi diffusion model. Water vapour permeation studies indicated that the water vapour transport rate through free films is directly related to the drug release rate. DSC thermograms and IR spectras revealed that there is no interaction between rifampicin and other additives. SEM photographs of coated beads, before dissolution and after dissolution, also indicates that the drug release mechanism follows diffusion model.

Topics: Cellulose; Delayed-Action Preparations; Enzyme Inhibitors; Microscopy, Electron, Scanning; Microspheres; Permeability; Plasticizers; Rifampin

The purpose of this study was to investigate the possibility to develop different levels of correlation between in vitro dissolution parameters and in vivo pharmacokinetic parameters for three rifampicin formulations. A level A correlation of in vitro release and in vivo absorption could be obtained for individual plasma level data by means of the Wagner and Nelson method. Linear correlation could be obtained when percent dose released in vitro was plotted vs percent dose absorbed in vivo with correlation coefficients between 0.954,0.983 and 0.997 for the formulations studied. A second level correlation between mean in vitro dissolution time (MDT) and mean in vivo residence time (MRT) was performed with a correlation coefficient of 0.536,0.420 and 0.335. Finally, it was also possible to establish a good in vitro-in vivo correlation when the T(50%hrs) (time taken to release 50% of rifampicin) in vitro and C(max),T(max) or AUC in vivo were compared.

Topics: Absorption; Adult; Algorithms; Antibiotics, Antitubercular; Area Under Curve; Cellulose; Humans; Male; Microspheres; Particle Size; Rifampin; Solubility