As far as absorption, no I have never seen any evidence of this. And 5-HTP needs to be taken on an empty stomach as where niacinamide needs to be taken with food.
Where niacinamide can play a role is by inhibiting the breakdown of serotonin. But there is a catch. Too much niacinamide can interfere with serotonin production by accepting methyl groups resulting in less methyl groups being available for serotonin production. So there has to be a balance between the intake of 5-HTP and niacinamide, or an increase of methyl donors to prevent the inhibition of serotonin by excess niacinamide.
- an increase in TMG should do the trick right?
Yes, this will work to donate methyl groups.
For one dose, yes that is very excessive. The maximum for a single dose I would recommend is 100mg, which can be done three times daily. Keep in mind though that increasing serotonin will treat premature ejaculation, but it will also reduce the sex drive. This is why selective serotonin reuptake inhibitors (SSRIs) used to treat some forms of depression are notorious for killing the sex drive.
- yeah I noticed that it actually made it a lot more flaccid when I took that dosage. what other things do you suggest to get my serotonin up / help overall with reversing my PE?
To raise serotonin you could go with chamomile, which is the richest source of tryptophan, the precursor for serotonin.
There are other ways to treat PE though. For example, the herbs dodder seed or unripe mulberry fruit (fu pen zi) can work great for treating PE.