Methylphenidate making amphetamines less effective?

The original question was not related to abusing anything, it was simply me asking if there was any specific reason why vyvanse has no theurapeutic effect for me, no matter the dosage. It was not about tolerance or abuse.

I'm not saying that I have too high of a tolerance, either. I get the desired theurapeutic effect from taking only one 10mg IR ritalin tablet, which I doubt should be stronger than 70mg lisdexamphetamine, considering 10mg mph is a very common dosage, some (like my brother) can even take 5mg in the morning and 5mg later in the day and still get the effect he needs, norwegian laws say that a daily mph dosage should not be higher than 80mg, unless it is really needed (I'm on max 100mg/day, as the effects of a 40mg SR capsule which is supposed to last 4-8 hours, never lasts more than 3-4 hours for me, and its been that way since the first time I took it), whilst 70mg lisdexamphetamine is the highest daily (legal) dose, at least here in Norway.

I've heard there can be issues related to lisdex and too high stomach acidity, could that be the problem?

/r/AskDrugNerds Thread Parent