A rule of unity for human intestinal absorption 3: Application to pharmaceuticals

Raj B. Patel, Samuel H Yalkowsky

Research output: Contribution to journalArticlepeer-review


The rule of unity is based on a simple absorption parameter, Π, that can accurately predict whether or not an orally administered drug will be well absorbed or poorly absorbed. The intrinsic aqueous solubility and octanol–water partition coefficient, along with the drug dose are used to calculate Π. We show that a single delineator value for Π exist that can distinguish whether a drug is likely to be well absorbed (FA ≥ 0.5) or poorly absorbed (FA < 0.5) at any specified dose. The model is shown to give 82.5% correct predictions for over 938 pharmaceuticals. The maximum well-absorbed dose (i.e. the maximum dose that will be more than 50% absorbed) calculated using this model can be utilized as a guideline for drug design and synthesis.

Original languageEnglish (US)
Pages (from-to)67-74
Number of pages8
JournalBiopharmaceutics and Drug Disposition
Issue number2
StatePublished - Feb 2018


  • absorption parameter
  • aqueous solubility
  • drug dose
  • human intestinal absorption
  • octanol water partition coefficient
  • rule of unity

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science
  • Pharmacology (medical)


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