Dynamics of dissolution and diffusion-controlled drug release systems

Laurent Simon, Parimala Bolisetty, Maria N. Erazo

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Analytical expressions were derived to explain the influence of the dissolution/diffusion number (Di) on the time constant and steady-state flux when dispersed drugs are released from a finite matrix. A key novelty of this work is the introduction of a single time-constant that combined the analysis of both dissolution- and diffusion-based systems. Focus is placed on systems with a constant dissolution rate and diffusion coefficient. Solutions, based on the residue theorem, were in agreement with published results describing the transport of estradiol in a polymeric matrix. The experimental cumulative amount of drug released was 0.1 mg/cm2 in 100 hours compared to 0.084 mg/cm2 predicted by the theoretical model. The process time constant, estimated from the first eigenvalue (t0) and a more accurate statistical approach (teff), showed a consistent decrease with increasing Di values. For a dissolution/diffusion number of 0.21, t0 and teff were estimated at 58.44 and 73.02 hrs, respectively. With the presence of a skin layer, teff increased to 575.7 hrs. These results can be used to assess the relative impact of dissolution and diffusion on the time it takes drugs to attain a therapeutic level in the bloodstream.

Original languageEnglish (US)
Pages (from-to)144-151
Number of pages8
JournalCurrent Drug Delivery
Issue number2
StatePublished - 2011

All Science Journal Classification (ASJC) codes

  • Pharmaceutical Science


  • Dissolution/diffusion number
  • Time constant
  • Transdermal


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