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Strange values for partition coefficient #353

MahmoudM3anl3ss opened this issue Jun 26, 2019 · 1 comment


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commented Jun 26, 2019


I'm new to using Pk-sim, just practicing with a basic PBPK model for clofazimine, which his highly lipophilic drug that accumulate mainly in adipose and fatty tissues mainly metabolized by liver (Cl : 0.26 l/h/kg)
given the published physicochemical characteristics of the drug,

Effective M.w: 429 (drug bank)
Fu : 0.01 (published study)
Logp : 7.66 (drug bank)
Water solubility : 0.233 mg/l (drug bank)
PKa is 8.6
When Pk-sim calculate (B/P ratio and Pc's), it gives me strange values, for example the B/p value of > 1 (2615.2) which I know is not correct, but if I log10 the value I get reasonable values for B/p ratio and Pc's.

What I'm missing or doing wrong ?




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commented Jun 26, 2019

Some initial thoughts:

In our experience, DrugBank LogP is often too high by some margin. LogD (@ph 7.4) or LogMA is more likely to be the right input for PK-Sim.
Also an fu of 0.01 is probably measured with high uncertainty. Increasing fu should also lower B:P.

What Partitioning Calculation Method did you use? For a highly lipophilic drug, I would recommend Rodgers and Rowland.

If you have data for B:P try first setting R&R as the calculation method, then decrease lipophilicity (Calculated LogP of ~7 often compare to LogD ~5) and maybe increase fu and see where you end up.

Hope this helps,

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