Posted by mtdewcmu on November 26, 2009, at 23:52:21
In reply to Prozac not potent 5-HT2C antagonist, posted by conundrum on November 26, 2009, at 10:43:21
> We have been speculating that prozac is a potent 5-HT2C antagonist however according to the study below it appears to be only a moderate 5-HT2C antagonist. Low dose prozac probably won't do much but block the reuptake pumps. Subjectively, 5mgs Prozac felt similar to 5mg lexapro but maybe not as strong and taking longer to kick in with less start up side effects.
>
> Fluoxetine's(Prozac) affinity for the serotonin transporter is Ki=1.4 nmol in vitro. Its affinity for 5-HT2C is Ki=64nmol. The smaller the number the more tightly the drug binds to the target. This means that prozac is a potent reuptake inhibitor and only a moderate 5-HT2C antagonist
>
> Ki=64nmol isn't very strong and at low dose of fluoxetine it probably wouldn't be noticable, but at a higher dose it should kick in, but you would have significant SRI at that point. You could try to add buspar to counter fluoxetine's serotonin enhancing effects but it only works for a few hours and then the serotonin would increase again after the drugs 5-HT1a's agonist properties wear off.What matters most is the ratio of the two affinities. According to your numbers, Prozac is about 46 times more potent as a 5-HT reuptake blocker as it is a 5-HT2C antagonist. That suggests that at therapeutic doses, there will not be significant 5-HT2C inhibition.
Although, Prozac continues to build up in your system for about a month, so it seems to me that by the time you reach steady state you may have a large excess of Prozac in your brain.
poster:mtdewcmu
thread:927037
URL: http://www.dr-bob.org/babble/neuro/20091104/msgs/927122.html