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Re: more on my Delersonalization experience » hello123

Posted by ed_uk2010 on February 1, 2015, at 7:55:28

In reply to Re: more on my Delersonalization experience, posted by hello123 on February 1, 2015, at 0:24:20

> > Oh right. Cyproheptadine is a more potent antihistamine than nortriptyline. Desipramine has little antihistamine effect.
> >
>
> Ed, do you have any of the number for Desipramines affinity for the Histamine receptor?

Yes, but remember, affinity values are of no meaning in isolation. The pharmacological effects of a drug depend on the concentration of the drug achieved at the receptor site in vivo, as well as the affinity, and a drug's comparative affinity for other sites is very important.

Different experiments come up with somewhat different results, but out of all sites, desipramine has the highest affinity for the human NE transporter, with a Ki of approximately 2. Remember that affinity values are of no meaning in isolation, but potentially useful for the comparison of a specific drug's binding to different sites. The affinity of desipramine for the human H1 histamine receptor is many times lower than its affinity for the NE transporter, with a Ki of around 60. Do not use Ki affinity values to casually compare the affinity of different drugs for the same site, because different drugs achieve very different concentrations at the receptor.

Anyway, the point is, because desipramine binds to human brain NE uptake sites with far higher affinity than H1 sites, it is possible to achieve reuptake inhibition with very little antihistamine effect. This is noticeable clinically; desipramine is unlikely to cause a subjective antihistamine-type sedation. Bear in mind, a lot of the subjective effects of antihistamine such as diphenhydramine are not due to H1 antagonism (these drugs are not selective)... many of the subjective effects are anticholinergic.

It's interesting that one of the drugs you have benefited from a great deal is a potent antihistamine, cyproheptadine. No doubt its benefits on mood were not due to histamine antagonism, however. Cyproheptadine has affinity for the 5-HT2a receptor with a Ki of around 1, which may be relevant. Its affinity for the H1 histamine receptor is extremely high, at around 0.06.

 

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