I have tried all kinds of things in the past to reduce tolerance/potentiate/alter pharmacokinetics of opioids and etc., and I found nothing truly works.
A tremendous caveat here is that these efforts were not made in pursuit of increasing the analgesic effects (since I have never suffered chronic pain, at least not beyond existential dread). My attempts were all made in the pursuit of additional subjectively "enjoyable effects", as well as increased sedative effects. Even things that work well on paper, like taking fluvoxamine on a daily basis while on methadone (which is known to significantly increase methadone blood levels, even dangerously so) never seemed to do a while lot for me.
But again, I can't weigh in from a pain control perspective though, only in my attempts to increase the euphoriant and sedative effects of narcotics. Black seed oil definitely does potentiate kratom, though my guess this is probably more of an additive effect given that both black seed oil and kratom are both fairly notable calcium channel (VDCC) blockers. But the effect is short-lived.
By the way, I can't imagine any situation where someone would overdose on a dose of an opioid that they wouldn't otherwise overdose on simply because they took some biotin or omega-3 fatty acids (as the OP suggested). That isn't possible.
I'd also caution against zinc supplements if you are on benzodiazepines, in benzo withdrawal or have suffered serious benzo withdrawal in the past, since it can have anti-GABAergic effects which can definitely be felt by those with impaired GABA-A receptor function. Zinc makes me pretty anxious in any significant amounts. Took me a while to figure, but each time I took this one zinc supplement (i believe each capsule contained 90mg of zinc in chelated and other forms) I'd feel very edgy. Eventually did some research and turns out there is a mechanism behind it.
Zinc is an abundant trace metal in the hippocampus nerve terminals. Previous studies demonstrate the ability of zinc to selectively block neurosteroid…
www.sciencedirect.com
Shouldn't be a problem for most people though. But again, my view is that trying to potentiate the euphoriant effects of opioids is a lost cause (yet I can't speak to efforts to enhance the analgesic effects in the treatment of chronic pain).