Bioequivalence and Bioavailability Forum

Ratnakar,

A subject is a PK outlier if his/her concentration time profile contains at least one concentration value that is very high or very low.
PK outliers can be the result of:

1. a statistical anomaly (happened by chance),
   
2. a product failure, (eg formulation released too much or too little drug)
   
3. a protocol violation (eg patient chewed tablet instead of swallowing it)
   
4. a subject by formulation interaction. A subject by formulation interaction exists when a subject "interacts" with the drug in a manner that is different than other subjects. For example, one subject may absorb the drug to a greater extent than other subjects in the study.

An outlier can only be excluded if it is clearly the result of a protocol violation. Documentation of the violation is required.

Caution should be used when excluding outliers, due to the potential for bias.

You can obtain more information at the URL shown below, which contains a summary of a meeting that was held on PK outliers. Power Point slides for some of the presentations are available.

http://www.hc-sc.gc.ca/dhp-mps/prodpharma/activit/sci-com/bio/sacbb_rop_ccsbb_crd_2004-06-03-eng.php

Greg

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