Posted by Brainbeard on September 16, 2009, at 8:42:46
In reply to Re: imipramine ) Inhibition of 5-HT Uptake Pump (%), posted by sowhysosad on September 15, 2009, at 22:00:46
> According to Preskorn it [imipramine, BB] has less affinity for the serotonin uptake pump than all of the SSRI's but is equal to venlafaxine.
That ain't right. Are you sure Preskorn said that? Got a link? Look at the table in this article by Gillman: http://www.psychotropical.com/Dual_action_drugs.shtml. Imipramine has an affinity for 5HT between 1.3 and 20, whereas venlafaxine has an affinity between 7.5 and 102 (the lower the number, the higher the affinity). Imipramine is obviously a much more potent SRI than venlafaxine (Effexor).
Ah, here is the article I was referring to: http://www.psychotropical.com/Antidepressants_Receptor_affinities_1.shtml
Gillman gives this list:
'Potency as 5 HT reuptake inhibitors (highest to lowest)
Paroxetine 0.13 Clomipramine 0.28
Sertraline 0.29 Fluoxetine 0.81
Citalopram 1.16 Imipramine 1.4Fluvoxamine 2.2 Amitriptyline 4.3
Dothiepin 8.6 Venlafaxine 8.9'Here you can see that fluvoxamine (Luvox) ranks lower than imipramine for SRI potency, while venlafaxine ranks absolute lowest of all the SRI's. Venlafaxine is a bit of a mystery, since it is known to be able to cause serotonin syndrome, while its affinity for 5HT (serotonin) is actually pretty weak. There may be some other, unknown mechanism at play.
> It [imipramine, BB] has stronger affinity for the noradrenaline uptake pump than for serotonin. Presumably you'd need to achieve almost 100% occupancy of the noradrenaline pump before the serotonin kicked in.No, imipramine is a moderate SRI, so the serotonin will kick in soon enough. At the usual therapeutic doses (say, 150mg), full SRI will certainly be at play.
> Certainly when I took 150mg I felt the agitated panicky noradrenaline effects but couldn't discern any serotonin.
Despite your experience, the fact that imipramine causes sexual dysfunction in therapeutical doses illustrates that it has potent SRI action. The sexual dysfunction is a typical effect of SRI. Fluvoxamine causes the least sexual dysfunction of all (S)SRI's, which is not surprising seeing that it is weaker than imipramine.
> It's active metabolite, desipramine, is also an NRI not an SSRI/SNRI, so I wonder if that would also affect things?
The NRI, which is indeed strong with imipramine, might overshadow the SRI (which doesn't mean that it's not there).
Cheers,
Brainbeard
poster:Brainbeard
thread:909605
URL: http://www.dr-bob.org/babble/neuro/20090701/msgs/917346.html