AlphaOdure said:
Propoxyphene is rough on the cardiovascular system & heart in general, but not b/c of its opioidergic action... b/c of its effects as a local anesthetic & a sodium channel blocker, it affects QRS intervals (and subsequent QT intervals). And this particular action isn't shared by methadone or levacetylmethadol to my knowledge, & i've read a lot on both of these drugs over the years... But feel free to correct me w/ sources if they're sodium channel blockers. And relative to other full agonists, methadone & levacetylmethadol, aren't shown to have that much of a difference on the cardiovascular system.
Your right that the bad heart related side effects mostly don't come from mu agonism. Methadone(
http://www.ncbi.nlm.nih.gov/pubmed/12820821) , LAAM and propoxyphene, all have some local anesthetic effects, but the QT prolongation is from their action on the potassium channel, particularly hERG. Propoxyphene also works on the potassium channels,
http://www.ncbi.nlm.nih.gov/pubmed/10690289 . Methadone's not too bad at under 200mg for most people, but LAAM can caused heart problems at therapeutic doses.
LAAM was withdrawn from the market for heart problems. Kind of sad because 2-3x a week dosing would be convent for some and maybe easier to taper off, good because it probably might have less euphoria than methadone and slowly metabolizes into something stronger and would probably causes ODs.
Even with the usually small risk of heart problems, methadone is the lesser evil compared to abusing street drugs. You're far more likely to die from an OD.
Levomethadone is more potent and has less of an effect on the heart. I think they should use L-methadone for at risk patient. Fuck I think for those requiring high doses they should seriously consider diamorphine or hydromorphone maintenance therapy. None of this is likely to happen soon in the USA.
My theory is a social mania as a result of those strings of deaths supposedly related to methadone use here in the US
My theory for the ODs is a combination of noobs underestimating it strength(many mistakenly think that because it's for detox it's weak), taking more before it fully kicks in, and users mixing with other it downers and uppers.
And yes, tolerance has a lot to do with this effect (well, w/ QT interval prolongation that is) in opioids in general. Its related to respiratory depression, at least to some extent.
QT interval prolongation has almost nothing to do with respiratory depression or tolerance. I assume that if someone's taking 200mg+ of methadone they have a tolerance.
And to get back on top, it'd make sense that an NMDA antagonistic or monoamine reuptake inhibiting opioid might have anti-depressant effects, since drugs of those classes have been shown to have antidepressant effects.
Buprenorphine and cyclazocine have been shown in some studies to have an antidepressant effect. Have they been compared to full mu agonists? I guess it could be argued that full mu agonist are a really fast acting antidepressant:D. Considering some of the drugs and procedures they use for depression, perhaps if someone's suffering from severe unrelenting depression opioids might be an option.