Why does half life have no correlation with how long something lasts?

[Addyman]

Example

I take a 10mg Adderall IR
It will last 4 hours when I have no tolerance

Yet the half life is 12 hours for dex/levo amphetamine



HM?



I suppose the half life DOES have something to do with how long you 'feel' it but I feel its only 50/50

 

[Jabberwocky]

I think drug in the bloodstream and amount of activity with receptors, gates, neurons etc only have a partial correlation.

Bi-phasic half-lives, individual cyp responses, auto-induction, different clearance rates and all kinds of other situations likely make textbook half-lives not all that exact to begin with.

 

[Psychedelic Jay]

I think drug in the bloodstream and amount of activity with receptors, gates, neurons etc only have a partial correlation.

Bi-phasic half-lives, individual cyp responses, auto-induction, different clearance rates and all kinds of other situations likely make textbook half-lives not all that exact to begin with.

In simple words, No. LOL Just in case you didn't understand all that.

 

[amapola]

It depends on the drug as Enki said. Sometimes the half life is useful on it's own and sometimes not.

Alcohol metabolism in the liver reaches its limited rate quite easily. It then follows zero order kinetics for processing (so T1/2 doesn't apply) but the effects are quite dependent on the plasma concentration.