Posted by SLS on June 7, 2005, at 16:13:50
In reply to Re: Seroquel Pharmacology question » ed_uk, posted by chess on June 7, 2005, at 14:33:22
Hi Chess.
How have you been?
> how can its effect last for up to 20 hours if its half-life is only 6 hours?
Although I think you are right in the case of Seroquel, it doesn't always follow that the biological activity of a drug is determined by its half-life. For instance, Parnate has a half-life of approximately 2 hours. Yet, its biological activity persists for days. Because it binds irreversibly to its target, its biological activity becomes more dependent on the body's ability to replace the target than to the removal of the drug from the blood stream.
With Seroquel, the drug does not bind very tightly to the dopamine receptor. In fact, it is the "weakest" of the atypical antipsychotics. It is constantly jumping on and off the receptor. My guess is that its activity is most dependent on the levels of drug in the blood stream, assuming that no other factors impede its exit from tissues. I imagine this is why Seroquel can make such an excellent sleep medication at dosages of 25-50mg. Come morning, most of the Seroquel is gone, and the person is able to start their day without too much residual sedation.
- Scott
poster:SLS
thread:509023
URL: http://www.dr-bob.org/babble/20050606/msgs/509212.html