Getting a full course of medicine into your pet is what makes it work. Ask your vet whether the medicine can be given with food, crushed or made into a liquid, chew or gel; many medicines can be compounded into easier forms, but some shouldn't be crushed.
For cats in particular, pills can stick in the oesophagus (food pipe) and cause irritation or narrowing, which is why vets recommend following any dry pill with a little water or food.
