Drug intake time according to metabolites found

[Fabs]

I was wondering if there is a way to find out through a Gas Chromatography how long, either in hours or days, the donor of a urine sample being tasted has been high on the drug found thru the amount of metabolites and raw drug excretion found.

Thank you

[Peter Apps]

In principal this is straightforward - quantify the drug metabolites and then calculate back to the time and quantity of intake using the anything that is known about the pharmacodynamics of the drug in question.

Peter

[Fabs]

You are saying that this is feasible and it is a standard procedure?

[Peter Apps]

Hi Fabs

Feasible - yes, standard procedure - that depends.

There are well established standard procedures for quantifying drugs in body fluids by GC (a relatively small number) and HPLC (nearly all of them).

For nearly all drugs the rates at which they are metabolised and excreted is more or less well known (this knowledge is required for the drugs to be registered). Because people are biological systems there is wide interindividual variability in drug kinetics/dynamics, which leads to a wide variability in calculations of how much drug was injested and when. The accuracy of the calculations depends much more on the biological variability than on the chemical analysis.

Peter