I cut my dog's pills. I know some medications you aren't supposed to because it doesn't actually do anything(you don't get half the medication just by cutting it in half--you still get the full dose).
Some medications are not supposed to be cut because they are designed to be time-released, and cutting them affects their ability to release slowly into the bloodstream. Always best to ask a pharmacist before cutting a pill.
I agree with Emily. Many pills are meant to be absorbed over time and some could even do damage to your throat when swallowed if cut. There's good reason why some pills are coated! Definitely check with your Dr.