Q. Can one who is sleepy and tired take a Pep or stimulant pills during Shabbos?
A. Shemiras Shabbos K’ (34: 31) quoting Minchas Yitzchok (3: 21) prohibits Pep or stimulant pills during Shabbos. (see also 39-Melochos 2 p. 497).
Horav Shlomo Miller’s Shlit’a opinion is that they are permitted when needed.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a