### Abstract

Purpose. The relationship between the pH, solubility, and partition coefficient was investigated to show that the product of intrinsic values of solubility and partition coefficient is equal to the product of total values of solubility and distribution coefficient at different pH. Methods. The pH distribution profiles were obtained from the literature and the pH solubility profiles were obtained from the literature or calculated from their intrinsic solubility and pK_{a}. Results. The pH solubility and pH distribution coefficient profiles of 25 compounds were investigated to show that the product of intrinsic solubility (S_{W}) and intrinsic octanol-water partition coefficient (K_{OW}) is equal to the product of total solubility of a partially ionized solute (S_{T}) and its octanol-buffer distribution coefficient (K_{D}) at any pH where ion pair formation and salt precipitation are not present. Conclusions. The fact that S_{W}·K_{OW} can be used instead of S_{T}·K_{D} to model the absorption of partially ionized drugs in the gastrointestinal tract has important biopharmaceutical implications.

Original language | English (US) |
---|---|

Pages (from-to) | 1862-1866 |

Number of pages | 5 |

Journal | Pharmaceutical Research |

Volume | 19 |

Issue number | 12 |

DOIs | |

State | Published - Dec 1 2002 |

### Fingerprint

### Keywords

- Absorption potential
- Octanol-buffer distribution coefficient
- Octanol-water partition coefficient
- pH
- Solubility

### ASJC Scopus subject areas

- Chemistry(all)
- Pharmaceutical Science
- Pharmacology

### Cite this

*Pharmaceutical Research*,

*19*(12), 1862-1866. https://doi.org/10.1023/A:1021449709716

**Independence of the product of solubility and distribution coefficient of pH.** / Ni, Nina; Sanghvi, Tapan; Yalkowsky, Samuel H.

Research output: Contribution to journal › Article

*Pharmaceutical Research*, vol. 19, no. 12, pp. 1862-1866. https://doi.org/10.1023/A:1021449709716

}

TY - JOUR

T1 - Independence of the product of solubility and distribution coefficient of pH

AU - Ni, Nina

AU - Sanghvi, Tapan

AU - Yalkowsky, Samuel H

PY - 2002/12/1

Y1 - 2002/12/1

N2 - Purpose. The relationship between the pH, solubility, and partition coefficient was investigated to show that the product of intrinsic values of solubility and partition coefficient is equal to the product of total values of solubility and distribution coefficient at different pH. Methods. The pH distribution profiles were obtained from the literature and the pH solubility profiles were obtained from the literature or calculated from their intrinsic solubility and pKa. Results. The pH solubility and pH distribution coefficient profiles of 25 compounds were investigated to show that the product of intrinsic solubility (SW) and intrinsic octanol-water partition coefficient (KOW) is equal to the product of total solubility of a partially ionized solute (ST) and its octanol-buffer distribution coefficient (KD) at any pH where ion pair formation and salt precipitation are not present. Conclusions. The fact that SW·KOW can be used instead of ST·KD to model the absorption of partially ionized drugs in the gastrointestinal tract has important biopharmaceutical implications.

AB - Purpose. The relationship between the pH, solubility, and partition coefficient was investigated to show that the product of intrinsic values of solubility and partition coefficient is equal to the product of total values of solubility and distribution coefficient at different pH. Methods. The pH distribution profiles were obtained from the literature and the pH solubility profiles were obtained from the literature or calculated from their intrinsic solubility and pKa. Results. The pH solubility and pH distribution coefficient profiles of 25 compounds were investigated to show that the product of intrinsic solubility (SW) and intrinsic octanol-water partition coefficient (KOW) is equal to the product of total solubility of a partially ionized solute (ST) and its octanol-buffer distribution coefficient (KD) at any pH where ion pair formation and salt precipitation are not present. Conclusions. The fact that SW·KOW can be used instead of ST·KD to model the absorption of partially ionized drugs in the gastrointestinal tract has important biopharmaceutical implications.

KW - Absorption potential

KW - Octanol-buffer distribution coefficient

KW - Octanol-water partition coefficient

KW - pH

KW - Solubility

UR - http://www.scopus.com/inward/record.url?scp=0036918103&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036918103&partnerID=8YFLogxK

U2 - 10.1023/A:1021449709716

DO - 10.1023/A:1021449709716

M3 - Article

C2 - 12523666

AN - SCOPUS:0036918103

VL - 19

SP - 1862

EP - 1866

JO - Pharmaceutical Research

JF - Pharmaceutical Research

SN - 0724-8741

IS - 12

ER -