I have a very strong headache. Happens to be I get very strong headaches when I fast. is it permitted to take a painkiller?
Yes it is permitted to take a pill or suppository painkiller If you need to take a little bit of water to get the pill down, that is also permitted
Emes L’yackov ftnt. 522, Halichos Shlomo 16- 6. M’bais Levi 13 pg. 57-5, There are poskim that say that if possible it is preferable to add something bitter to the water- see Chut Shani Shabbos 2- pg. 326.