### Abstract

The relationships between drug lipophilicity and hepatic intrinsic clearance (CL(int,h)) or red blood cell-plasma partition coefficients (D) have been elucidated for ten highly lipophilic basic drugs with apparent octanol-water partition coefficients at pH 7.4 (P(app,oct)) of 150 or above. The true octanol-water partition coefficients of the non-ionized drugs (P(oct)) were used to determine CL(int,h) and D for the unbound drugs (CL(int,h,f) and D(f), respectively), and CL(int,h,f) and D(f) for the non-ionized and unbound drugs (CL(int,h,fu) and D(fu), respectively). The total clearance values were determined at steady state by infusion studies of individual drugs in rabbits. There was better correlation between log P(oct) and log CL(int,h,fu) (r = 0.974) than between log P(oct) and log CL(int,h,f) (r = 0.864). The D values were calculated from the blood-plasma concentration ratio. There was a better correlation between log P(oct) and log D(fu) (r = 0.944) than between log P(oct) and log D(f) (r = 0.612). The regression equations obtained were CL(int,h,fu) = 0.0875 x P(oct)^{1.338} and D(fu) = 0.0108 x P(oct)^{0.970}, respectively. These results show that the CL(int,h) and D of highly lipophilic basic drugs can be predicted from P(oct) by taking f(u) into consideration. By applying these parameters to a physiologically based pharmacokinetic model it might be possible to predict the pharmacokinetics of unknown basic drugs.

Original language | English |
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Pages (from-to) | 768-772 |

Number of pages | 5 |

Journal | Journal of Pharmacy and Pharmacology |

Volume | 49 |

Issue number | 8 |

Publication status | Published - 1997 Aug |

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### ASJC Scopus subject areas

- Pharmacology
- Pharmaceutical Science

### Cite this

*Journal of Pharmacy and Pharmacology*,

*49*(8), 768-772.

**Relationships between the hepatic intrinsic clearance or blood cell-plasma partition coefficient in the rabbit and the lipophilicity of basic drugs.** / Ishizaki, Junko; Yokogawa, Koichi; Nakashima, Emi; Ichimura, Fujio.

Research output: Contribution to journal › Article

*Journal of Pharmacy and Pharmacology*, vol. 49, no. 8, pp. 768-772.

}

TY - JOUR

T1 - Relationships between the hepatic intrinsic clearance or blood cell-plasma partition coefficient in the rabbit and the lipophilicity of basic drugs

AU - Ishizaki, Junko

AU - Yokogawa, Koichi

AU - Nakashima, Emi

AU - Ichimura, Fujio

PY - 1997/8

Y1 - 1997/8

N2 - The relationships between drug lipophilicity and hepatic intrinsic clearance (CL(int,h)) or red blood cell-plasma partition coefficients (D) have been elucidated for ten highly lipophilic basic drugs with apparent octanol-water partition coefficients at pH 7.4 (P(app,oct)) of 150 or above. The true octanol-water partition coefficients of the non-ionized drugs (P(oct)) were used to determine CL(int,h) and D for the unbound drugs (CL(int,h,f) and D(f), respectively), and CL(int,h,f) and D(f) for the non-ionized and unbound drugs (CL(int,h,fu) and D(fu), respectively). The total clearance values were determined at steady state by infusion studies of individual drugs in rabbits. There was better correlation between log P(oct) and log CL(int,h,fu) (r = 0.974) than between log P(oct) and log CL(int,h,f) (r = 0.864). The D values were calculated from the blood-plasma concentration ratio. There was a better correlation between log P(oct) and log D(fu) (r = 0.944) than between log P(oct) and log D(f) (r = 0.612). The regression equations obtained were CL(int,h,fu) = 0.0875 x P(oct)1.338 and D(fu) = 0.0108 x P(oct)0.970, respectively. These results show that the CL(int,h) and D of highly lipophilic basic drugs can be predicted from P(oct) by taking f(u) into consideration. By applying these parameters to a physiologically based pharmacokinetic model it might be possible to predict the pharmacokinetics of unknown basic drugs.

AB - The relationships between drug lipophilicity and hepatic intrinsic clearance (CL(int,h)) or red blood cell-plasma partition coefficients (D) have been elucidated for ten highly lipophilic basic drugs with apparent octanol-water partition coefficients at pH 7.4 (P(app,oct)) of 150 or above. The true octanol-water partition coefficients of the non-ionized drugs (P(oct)) were used to determine CL(int,h) and D for the unbound drugs (CL(int,h,f) and D(f), respectively), and CL(int,h,f) and D(f) for the non-ionized and unbound drugs (CL(int,h,fu) and D(fu), respectively). The total clearance values were determined at steady state by infusion studies of individual drugs in rabbits. There was better correlation between log P(oct) and log CL(int,h,fu) (r = 0.974) than between log P(oct) and log CL(int,h,f) (r = 0.864). The D values were calculated from the blood-plasma concentration ratio. There was a better correlation between log P(oct) and log D(fu) (r = 0.944) than between log P(oct) and log D(f) (r = 0.612). The regression equations obtained were CL(int,h,fu) = 0.0875 x P(oct)1.338 and D(fu) = 0.0108 x P(oct)0.970, respectively. These results show that the CL(int,h) and D of highly lipophilic basic drugs can be predicted from P(oct) by taking f(u) into consideration. By applying these parameters to a physiologically based pharmacokinetic model it might be possible to predict the pharmacokinetics of unknown basic drugs.

UR - http://www.scopus.com/inward/record.url?scp=0030928558&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030928558&partnerID=8YFLogxK

M3 - Article

C2 - 9379353

AN - SCOPUS:0030928558

VL - 49

SP - 768

EP - 772

JO - Journal of Pharmacy and Pharmacology

JF - Journal of Pharmacy and Pharmacology

SN - 0022-3573

IS - 8

ER -