Posted by blackjack on July 4, 2001, at 14:50:31
In reply to why do antidepressants work?, posted by Edward on July 3, 2001, at 14:32:39
> I don't understand this: whenever you take drugs constantly for a prolonged period of time, you become tolerant.
That is not true of all drugs. Some drugs (marijuana comes to mind) actually produce a REVERSE tolerence, so the more you do it, the LESS you need to achieve the effect. Also, since many drugs affect several different systems, they sometimes create a tolerence to some of their effects, but not others. Most people will develop a tolerence to the euphoric effects of amphetamines, and to many of the peripheral side effects, like sweating and increased blood pressure, but the focus, enhancing and sleep-redcing effects are often sustained at the same dose for a person's entire lifetime. There are plenty of non-psychiaric drugs that people use for very extended periods of time that do not produce tolerence. It depends on the drug and, in part, the individual.
As has been stated by others, the process which often produces tolerence is one in which the brain adjusts its production of certain chemicals, or changes the number or nerve receptors for certain chemicals, in order to try to restore its previous ballance. It is thought, in the case of many antidepressants, that it is this very adjustment, not the immediate effects of the drugs, that is responsible for the sustained antidepressant effect. Prozac causes an almost immediate increas in seratonin levels (which is why the side effects start immediately) but it is not until several weeks later that the antideressant effects kick in. It is supposed (and, yes, there is a lot of guesswork) that this is because the increase in seratonin casues some other secondary changes in the brain over time.
Some people do develop a tolerence to some antidepressants, however. I began to develop withdrawal symptoms while still taking more than the maximum recommended dosage of the MAOI Parnate, and my depression returned. Increasing the dose did not help. I went off of it for a while, and when I went back on it, it worked as before for several months before the tolerence kicked in again. I have heard several other people who had simila experiences with MAOI's.
Likewise, there is a phenomenon called (technically :) "SSRI poop-out". People who have been taking an SSRI successfully for several months or even years will suddenly find that it no longer works. This may not be tolerence in the classic sense, but perhaps a reaction to a secondary change (e.g., decreased dopamine release) caused by chronic use of the SSRI in question.
poster:blackjack
thread:68829
URL: http://www.dr-bob.org/babble/20010701/msgs/68960.html