Until researchers discover the next great painkiller, what you may want to know right now is which drug to take for a pounding headache, cramps, back spasms, and sore joints. There can be vast differences in how individuals respond to a medication, so relief may require trial and error, says Scott Fishman, MD, chief of the division of pain medicine at the University of California, Davis. Still, a few guidelines will help you feel better faster: