Nuance pharmacokinetics question

[TestEinstein]

I know about all the rate/order and half-life calculations, but I have a question about the starting point...

When a compound has a half-life of, for example, 6 hours, does that mean that t1/2=6 hours after plasma concentration peak, or initial oral administration. I ask because there is a significant lag time with oral AAS, partially modulated by simultaneous lipid consumption, so if I take 20mg of Epi (40%BA so roughtly 8mg bioavailable) with a ~6 hour half life at 12pm as part of a meal, I want to know if it hits the t1/2 (roughly 4mg bioavailable) at 6pm or closer to 8pm.

Also, do 17aas and non-methylated drugs have a similar latency before peak plasma concentration? That is, does Epi/SD/HD peak in the blood stream more quickly/slowly than M-LMG or 4-AD, given a similar dosage weight? I ask because plasma metabolite ratios would conceivably be affected by delays.

Thanks in advance guys.

 

[TestEinstein]

Any thoughts?

 

[chocolatemilk]

half life is a measure of decay so if blood plasma concentration of a given molecule is rising to its peak there is no decay going on yet. once at peak, molecule decays and half life is measured

peak plasma concentration times of ingested drugs differ according to many factors

the metabolite ratios will equilibrate as more molecule is entering into blood plasma so there is no drastic changes in the system