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[John250]

I’m curious why naltrexone is the only antagonist used in low doses for benefits vs other opioid antagonists like naloxone,suboxone,etc..

[Kimer Med]

The theory behind the effectiveness of LDN is that it blocks opiod receptors for just long enough to cause the body to create more endogenous endorphins and enkephalins than it normally would. When the LDN wears off and opiod receptors are free again and the endogenous compounds take over, providing symptomatic relief (you can actually feel worse while the LDN is active).

 

Naltrexone has a half-life of about 4 hours, which fits well with the above pharmacodynamics. 

 

Naloxone is only effective for about 30 to 60 minutes, which means multiple doses would be required to achieve the desired effect.

 

Suboxone (Naloxone plus Buprenorphine) lasts for about 24 hours, which is too long.

 

IOW, Naltrexone sits in a nice sweet spot in terms of half-life / duration of effect. It's also a relatively old compound, and is therefore inexpensive, especially in low-dose form.