Bioequivalence and Bioavailability Forum

Dear chirayu,

As per my knowledge
Elimination half life : when drug get eliminated from body completely.
Apparent half life : generally i think we consern it with Cmax. when there is a amount of unbound drug can absorbed or goes or store in hepatobiliary circulations, when this amount of drug get start eliminated, we can call apparent half life.

this is what i think but not sure, so let me know if better ideas.

thankyou
regards
Dr.Tarak Parikh
MD, Physician
Sun Pharmaceuticals Ltd.

Dear Chirayu,

Apparent half life is used for metabolites, where what you calculate is not purely the real elimination half life of the metabolite but the combination of two phenomenon: the transformation of the parent compound into the metabolite and the elimination of this metabolite.

If the limiting factor is the elimination phase, and the terminal half life of the metabolite is longer than that of the parent compound, what you will calculate will be close to the actual elimination half life. On the other hand, if the real terminal half life of the metabolite is shorter than that of the parent compound and this is a predominant metabolic pathway, the elimination half life you will calculate for the metabolite will be about the same as that of the parent compound: you will see the metabolite appear at the same rate the parent compound is eliminated, and this will be dominant in your combination of transformation and elimination.

Regards
Ohlbe

Dear Chirayu,

I have already posted on apparent half-life. Elimination half-life is calculated using elimination rate constant by the relationship 0.693/Ke. Where Ke is elimination rate constant. It is essential first to understand what is elimination rate constant so that one can make out easily the meaning of elimination half-life. Kel is the rate constant describing the loss of unchanged drug from the systemic circulation by either elimination (if the drug is not metabolized), regardless of pathway of excretion, or by elimination, regardless of pathway of excretion, plus loss of unchanged drug due to metabolism. In the latter case we refer to it as the overall elimination rate constant, often termed K. OK!!!

drshiv

❝ what is the diffrence between apperant half-life and elimination half-life?

Dear Chirayu.

Hope you cleared your confusion by Dr Shiv's answer. It is really nice explaination.

Regards.

Dear Dr Shiv

Thank You very much for the explainations. Now the thing is cleared.

Regards.