Differences between SSRIs?
Chris Hedley
does anyone know if there're any really significant differences
of the effects of different SSRI medications? I don't mean the
sort of "well, one might work for you and another may not" type
of thing, but differences in their overall effects. For example,
paroxetine is thought to be a pretty powerful antidepressant with
various side-effects, whereas citalopram has less of the side
effects and allegedly has an anxiolytic property in addition to
its antidepressant effects. I've been on both of these (amongst
other things) and have now been prescribed sertraline, and it's
difficult not to think "oh it's just another SSRI."
Since I'm curious about the effects and dynamics of anything I'm
taking, I've done some reading up on psychopharmacology and have
a fairly basic understanding of some of the fundamentals, which
would appear to suggest that all drugs in this class do exactly
one thing: inhibit the neuronal reuptake of serotonin (as the
name implies) The literature accompanying the products usually
says "... has little or no affinity for noradrenalin or dopamine
reuptake or for 5HT1, 5HT2, alpha, GABA etc receptors" so is
there really any room for these medications to have any significant
unique properties? The drugs companies would appear to think so
as there's a myriad of these things available and more appearing,
but what alternatives does one SSRI offer over another?
Chris.
James MacLachlan
The difference mainly lay's in their power on serotonin receptors. Paxil
being the strongest...and hence may why it has such "serotonin related"
side effects. (ie. reduced sex drive/drowsiness, etc.) The following
chart shows the "strength" of many popular SSRI's on Serotonin
receptors, as well as some TCA's for comparison.
Drug
5-HT Transporter Affinity†
Histamine H1 Affinity§
Paroxetine
800
0.0045
Clomipramine
360
3.2
Sertraline
340
0.0041
Fluoxetine
120
0.016
Imipramine
70
9.1
Fluvoxamine
45
0.00092
Amitriptyline
23
91
Venlafaxine
11
0
Diphenhydramine‡
0.03
7.1
* Affinity is defined as 1/Kd x 1 x 10-7, where Kd= equilibrium
dissociation constant in molarity.
†Data adapted from Tatsumi et al6
§Data adapted from Richelson and Nelson1 and Cusak et al.2
‡This is not an antidepressant but is shown for comparison. Richelson,
E. Primary Psychiatry. Vol.
5 No. 1. 1998.
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James M.
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Chris Hedley escribió: