Comparison of the z-factor and Polli dissolution rate coefficient for monodisperse powders.

The Polli dissolution equation and the classical z-factor model both characterize the rate of drug dissolution via a rate coefficient (kd or z, respectively) and nominally possess the same units (e.g., mL/mg per min). The objective was to assess the numerical similarity of the dissolution rate coefficient kd in the Polli model to the z-factor in the z-factor model across a wide range of dissolution conditions. Firstly, simulated dissolution profiles of monodisperse particles were generated using the z-factor model under a range of drug solubility, drug or micelle diffusivity, and initial drug particle radius conditions. Each simulated profile from the z-factor model was fitted with the Polli equation, yielding fitted kd. Secondly, fits for each kd and z were obtained from previously reported dissolution profiles of different polydisperse drug powders into various media. From the simulation study, the fitted kd values were generally similar to z-factor values, in parameterizing powder dissolution profiles across a wide range of dissolution conditions. kd tended to be slightly larger than z, particularly for profiles with over 80% dissolved for the fixed diffusion layer thickness model. From fits to previously reported dissolution profiles, fitted kd and z values were very similar. Findings show that the one-parameter Polli equation provides an effective, simplified alternative to the z-factor model without a substantial change in parameter value in representing monodisperse or polydisperse particle dissolution across a wide range of dissolution conditions.

• Publication year

  2025

• Venue

  International journal of pharmaceutics

• Publication date

  2025-11-01

• Fields of study

  Medicine

• Identifiers
  DOI 10.1016/j.ijpharm.2025.126380PMID 41223954
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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