Psycho-Babble Medication | about biological treatments | Framed
This thread | Show all | Post follow-up | Start new thread | List of forums | Search | FAQ

Re: Half Live vs. Duration of Action mike99

Posted by Kon on November 12, 2005, at 18:45:03

In reply to Half Live vs. Duration of Action, posted by mike99 on November 12, 2005, at 9:16:32

> Can anyone explain how dextroamphetamine has a plasma half-life of approximately 10 hours yet it's duration of action is only 4-6 hours?

Because of redistribution of drug to other sites in the body other than central (brain) receptors.

> For example, if one took 10 mg, wouldn't you then have the effect of 5 mg ten hours later?

No...for same reason. A 5 mg immediate dose means a greater % of total drug hitting the central receptors because the drug hasn't fully distributed to the whole body so more can hit the brain receptors. With a 5 mg dose left over after 10 hours (half-life), a greater percentage of drug will be distributed to other body sites other than the brain. So while the same amount of drug is in body (5 mg), there will be less drug hitting brain receptors in the latter situation.

> I'm also curious how accumulation does not occur with a half-life over 5-6 hours or multiple daily dosings as my understanding is that 4-5 half-lives are required to eliminate a drug from the body.

There may be accumulation to some steady state blood level depending on dose, dosing interval and half-life.




Post a new follow-up

Your message only Include above post

Notify the administrators

They will then review this post with the posting guidelines in mind.

To contact them about something other than this post, please use this form instead.


Start a new thread

Google www
Search options and examples
[amazon] for

This thread | Show all | Post follow-up | Start new thread | FAQ
Psycho-Babble Medication | Framed

poster:Kon thread:577993