Posted by King Vultan on October 1, 2004, at 8:16:18
In reply to Parnate or Nardil Sedation, posted by TomG on September 30, 2004, at 23:46:22
> I know this happens, and I've tried to look in the archives to find the answer, but I was unsucessful.
>
> What is the thought on why sedation occurs with Parnate and to a lesser extent I think Nardil?
I think there are two possible answers. As I mentioned in another thread, I believe the afternoon drowsiness that can be caused by either med is related to the insomnia that is common with both of them. In my case with Nardil, the drowsiness went away when I started taking more powerful sleeping aids and getting more hours of sleep a night. Parnate seems to be regarded as worse for insomnia, so I suppose it would make sense for people to be more sleepy in the afternoons while on it.The other answer is considerably more complicated and has to do with the issue of hypersensitive dopamine autoreceptors that has been discussed here in the last month or so. There had been a link posted to a column talking about people who fall asleep upon taking stimulants like Ritalin and some of the amphetamines. The author hypothesized that these people had too many (inhibitory) dopamine autoreceptors, and the extra amount of dopamine being made available by these drugs was slowing the firing rate of their dopamine neurons to little or nothing, inducing sedation. Since Parnate has a virtually identical chemical formula and a very similar structure to that of amphetamine, one might theorize that it could induce the same effect.
I take Parnate and have not actually noticed this, however, even though I found the stimulant Provigil to be completely intolerable because it induced extreme sedation, IMO, very likely due to the mechanism described above. I will say that I have had to work through some bouts of depression on Parnate that occur after increasing the dosage; it seems clear that this transient depressant effect is related to the dosage increase, and I can't think of any other mechanism other than the drug stimulating autoreceptors on neurons and slowing down the firing rate. This appears to be an unfortunate but necessary part in the downregulation process, and as the number of autoreceptors diminish, the firing rate should speed back up. In my case, I honestly don't know if the depressive effect I've noticed is from stimulation of dopamine autoreceptors or those of another neurotransmitter; since Parnate works on serotonin, norepinephrine, and dopamine, it could theoretically be any of them, or even some combination.
Todd
poster:King Vultan
thread:397689
URL: http://www.dr-bob.org/babble/20040927/msgs/397800.html