Film-coated matrix mini-tablets for the extended release of a water-soluble drug

Drug Dev Ind Pharm. 2015 Apr;41(4):623-30. doi: 10.3109/03639045.2014.891128. Epub 2014 Feb 24.


Extended release (ER) of water-soluble drugs from hydroxypropylmethylcellulose (HPMC) matrix mini-tablets (mini-matrices) is difficult to achieve due to the large surface area to volume ratio of the mini matrices. Therefore, the aims of this study were to control the release of a water-soluble drug (theophylline) from mini-matrices by applying ER ethylcellulose film coating (Surelease®), and to assess the effects of Surelease®:pore former (Opadry®) ratio and coating load on release rates. Mini-matrices containing 40%w/w HPMC K100M CR were coated with 100:0, 85:15, 80:20, 75:25 or 70:30 Surelease®:Opadry® to different coating weight gains (6-20%). Non-matrix mini-tablets were also produced and coated with 80:20 Surelease®:Opadry® to different coating weight gains. At low coating weight gains, nonmatrix mini-tablets released the entire drug within 0.5 h, while at high coating weight gains only a very small amount (<5%) of drug was released after 12 h. The gel formation of HPMC prevented disintegration of mini-matrices at low coating weight gains but contributed to rupture of the film even at high coating weight gains. As a result, drug release from mini-matrices was slower than that from nonmatrix mini-tablets at low coating weight gains, yet faster at high coating weight gains. An increase in the lag time of drug release from mini-matrices was observed as the concentration of Opadry® reduced or the coating weight gain increased. This study has demonstrated the possibility of extending the release of a water-soluble drug from HPMC mini-matrices by applying ER film coating with appropriate levels of pore former and coating weight gains to tailor the release rate.

Keywords: Ethylcellulose; HPMC; film coating; hypromellose; mini-matrices; theophylline.

Publication types

  • Comparative Study

MeSH terms

  • Cellulose / analogs & derivatives*
  • Cellulose / chemistry
  • Cellulose / ultrastructure
  • Delayed-Action Preparations / administration & dosage
  • Delayed-Action Preparations / analysis
  • Delayed-Action Preparations / chemistry
  • Drug Compounding
  • Drug Delivery Systems*
  • Drug Liberation
  • Excipients / chemistry*
  • Gels
  • Hypromellose Derivatives / chemistry*
  • Kinetics
  • Microscopy, Electron, Scanning
  • Phosphodiesterase Inhibitors / administration & dosage*
  • Phosphodiesterase Inhibitors / analysis
  • Phosphodiesterase Inhibitors / chemistry
  • Polyethylene Glycols / chemistry*
  • Polyvinyl Alcohol / chemistry*
  • Polyvinyls / chemistry*
  • Porosity
  • Solubility
  • Surface Properties
  • Tablets
  • Theophylline / administration & dosage*
  • Theophylline / analysis
  • Theophylline / chemistry


  • Delayed-Action Preparations
  • Excipients
  • Gels
  • Opadry II 85
  • Phosphodiesterase Inhibitors
  • Polyvinyls
  • Tablets
  • Hypromellose Derivatives
  • Polyethylene Glycols
  • ethyl cellulose
  • Polyvinyl Alcohol
  • Cellulose
  • Theophylline
  • polyethylene glycol 3350