TL;DR: Used Methylphenidate (40mg XR) on a daily basis for 2 years, had consistently strong effects every time (with minor breaks in between), stopped Methylphenidate for 3 months, during these 3 months I took 400mg of Magnesium Citrate daily, after these 3 months I started requiring Magnesium to have effects from the Methylphenidate. If I now take Methylphenidate without Magnesium, I will feel absolutely NOTHING. This is also true about Caffeine and Alcohol now.
In February 2016, I started taking Magnesium Citrate. Sometimes I took 200mg daily, but most days I took 400mg daily. This was shortly after stopping my prescribed Methylphenidate, which I took for 2 years prior, daily, with very strong effects every time.
In May 2016, I was back to Methylphenidate, just for a month to get me through my finals. I still took Magnesium on a daily basis, and the Methylphenidate was quite potent in that month; definitely the strength I was used to, and even more.
I stopped again in June 2016, and went back to it in November 2016, this time without taking any Magnesium Citrate at all. Took it the first day after 5 months without it; no effects at all. Second day, again, no effects at all. No stimulation at all, and not even focus - I tried to focus but couldn't at anything.
This went on for a week, until one day I took 200mg of Magnesium Citrate together with my Methylphenidate. This day, I finally felt that strong stimulant effect I was used to, in addition to powerful focus.
Since then, I have noticed I am completely dependent on the Magnesium to feel any effect whatsoever from Methylphenidate. And not only Methylphenidate, I also feel nothing from Caffeine and Alcohol without it, now. I'm not talking about a weaker than usual effect; just zero, absolutely no effect at all without Magnesium, from these drugs.
I tried stopping Magnesium for 2 weeks to reverse this, but nothing changed. I was still dependent on it for that, after these 2 weeks.
By itself, Magnesium does not cause any noticeable effect for me; it's just that I need it now to feel stimulants and alcohol.
Has anyone here noticed anything similar? What could possibly cause this?