Estimation of drug precipitation upon dilution of pH-controlled formulations

Ryuichi Narazaki, Ritesh Sanghvi, Samuel H. Yalkowsky

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


An equation is developed for estimating the precipitation that may occur upon diluting or injecting a (pH-)solubilized drug formulation. Since it is based on equilibrium, it is the worst case scenario for precipitation. This equation can be programmed in any commercially available spread sheet program such as Excel. According to the proposed equation, the type and the strength of the buffer species are the most significant factors that affect the pH and solubility of a drug in its microenvironment during dilution. To demonstrate the utility and robustness of the proposed equation, experimental measurements were performed using phenytoin as the model drug. The result suggests that the proposed equation can be used to indicate the possibility and the degree of precipitation that would occur upon injection. This provides a useful tool for the design of a successful pH-controlled solution formulation.

Original languageEnglish (US)
Pages (from-to)550-555
Number of pages6
JournalMolecular Pharmaceutics
Issue number4
StatePublished - Jul 2007


  • Buffer
  • Estimation
  • Phenytoin
  • Precipitation
  • pH

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmaceutical Science
  • Drug Discovery


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