Do I have withdrawal from old kind or bad reaction to new kind?

Day before yesterday I ran out of the sublingual modafinil formulation I’d been taking (prescribed legitimately to a friend).

Yesterday morning I took 400mg of a new kind (pills from India) and within hours became quite sick. The main symptoms were violent chills, stomach pain and diarrhea, though I also (strangely) had a terrible exzcema outbreak.

Today I feel better and, for the first time in months, haven’t taken any modafinil (which perhaps I should embrace as my off-ramp from this medication — but I’m so tired).

I’m wondering if I was experiencing withdrawal from the old version or a bad reaction to the new version —- or maybe both? I also realized that I took twice as much as usual by mistake as the new pills were 200mg as opposed to 100mg like the old ones.

Or maybe I just had the flu?