Dear Colleagues,

We all know that, Pharmacokinetic and Toxicokinetic properties of a chemical entity will have pivotal role in deriving the ADE/PDE/OEL and other health based exposure limits.

In this post, my question is about how to fix the the Toxicokinetic (TK) factor levels while calculating the OEL of a chemical entity.

If the test substance is 100 % bio-available by oral route and expected route of exposure say Inhalation, then we need not to give any consideration, and hence we use '1' as a TK factor.

Here are the few real time situations where we often confused/puzzled in fixing the TK factor and thereby deriving the OEL.

1. Suppose the test substance has oral bio-availability of 90% and we do not have much information about the bio-availability of test substance related to its possible route of exposure such as inhalation route, how to negotiate in fixing the TK factor in calculating the OEL ?

2. Secondly, if the oral bio-availability is less (approximately 30%) and there is no data available on the bio-availability of test substance related to its possible route of exposure, such as inhalation route, in these scenario how to fix the TK factor in calculating the OEL ?

Regards

Vishwanatha