Posted by linkadge on August 12, 2007, at 21:45:00
In reply to Re: Vicodin and Percocet for Depression, posted by Quintal on August 12, 2007, at 17:05:15
>Tolerance is simply the adaptation of >neurotransmitter systems to chronic exposure of >a drug.
Well, sometimes the adaptive changes that take place with certain drugs is actually related to the theraputic effect. The brain adapts to chronic SSRI treatment by reducing the number of postsynaptic serotonin receptors. Despite this adaptive responce however, many individuals continue to attain a theraputic effect.
Sometimes euphoria is a side effect of conventional antidepressant treatment too. Nardil can induce temporary euphoria, as can Parnate. Euphoria with these drugs is a side effect and unrelated to the long term theraputic effect.
There have indeed been studies of opiate treatment for depression. Many times such studies end without reaching the same conclusions that are followed in common practice.
Some recent research has suggested that morphine is as effective as imipramine for endogenious melancholic depression, and that a theraputic effect can be maintained untill treatment ends.
Some researchers have noticed that opiates produce the same, long term alterations in EEG measures (ie EEG slowing) that occur during sucessfull TCA treatment which persists until treatment ceases.
As mentioned in previous posts, opiates effect neurotransmitter systems in ways that are not completely understood as of yet. Opiates appear to increase the activity of tryptophan hydroxylase, as well as altering levels of monoamine oxidase B. Their effects on tryptophan hydroxylase appear to be long term in nature. Opiates also appear to affect the glutate transporter, which may be a theraputic mechanism of certain SSRI's and hypericum.
Opiates can reduce stress induced anhedonia in animal models, as well as reducing stress induced hyperactivity of HPA axis function. They increase serotonin levels in the neucleus accumbens as do other antidepressant treatments.
As mentioned by another poster, opiate withdrawl can be prevented by d2 receptor modulation. Sucessfull treatment with either SSRI's or TCA's is generally though to be dependant on upregulation of limbic d2 receptor affinity. Sucessfull treatment with SSRI's or TCA's can be blocked by preventing this upregulation.
The behavioral effects of the opiates can also be blocked by d2 receptor modulation indicating that a similar theraputic end target exits for both treatments.
Clearly, it is not rational to squelch the possablity of a theraputic effect of the opiates seing as we cannot, as of yet, completely quantify their mechanism of action.
Looking purely from a standpoint of abuse, opiate use is probably a dead end. There are, however, many drugs of abuse for which tollerance to a theraputic effect is not always the rule.
Drugs such as amphetamines, or ritalin can be easily abused and tollerance often develops to the euphoric effects. Used in children with ADHD however, the drugs can be used for extended periods of time long after the euphoriant effects have subsided.
Tolerance to euphoric effects of many drugs would appear to be the rule, but as many authors have suggested, there may infact be mechanisms of activity of the opiates (such as with the stimulants in ADHD), that are affecting some critical aspect of the affective process.
Linkadge
poster:linkadge
thread:775567
URL: http://www.dr-bob.org/babble/20070808/msgs/775884.html