Combinations - Speed & Zoloft

[kill]

Swim took speed for the first time on Friday, 7 lines in a period of about 2 hours.
Swim felt nothing from this whatsoever.
No "speeding" or euphoria or anything at all.

Swim cut it so swim knew how much filler was in it.
Swim is on antidepressants, one named Zoloft. a 50mg per day dosage. However swim has only been on these medications for 3 weeks to a month.

Is this why swim experienced no effects of the speed?
Any advice for swim in the future?

E.g: next time swim wishes to do speed to not take zoloft for a week prior? Do more lines next time, etc?

Also: Swims friends who used it felt the usual effects of speed, they have used previously.