title: Dynamics of dissolution and diffusion-controlled drug release systems.
abstract: 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 (t(eff)), showed a consistent decrease with increasing Di values. For a dissolution/diffusion number of 0.21, t0 and t(eff) were estimated at 58.44 and 73.02 hrs, respectively. With the presence of a skin layer, t(eff) 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.
authors.affiliation: Otto H. York Department of Chemical, Biological and Pharmaceutical Engineering, New Jersey Institute of Technology, Newark, NJ 07102, USA. laurent.simon@njit.edu
authors.forename: Laurent
authors.initials: L
authors.lastname: Simon
authors.forename: Parimala
authors.initials: P
authors.lastname: Bolisetty
authors.forename: Maria N
authors.initials: MN
authors.lastname: Erazo
mesh_terms: D001692:Biological Transport; D003692:Delayed-Action Preparations / Q000737:chemistry* / Q000493:pharmacokinetics*; D004058:Diffusion; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D012867:Skin / Q000378:metabolism*; D012995:Solubility; D057968:Transdermal Patch
chemical_list: D003692:Delayed-Action Preparations