Oliver is Very Stubborn

Oliver is a very stubborn, hard headed cat. I realized the other day he has tapeworms - that is why he eats so much. Andy got some pills Thursday when he went to town. He fed him a little bit of food Friday morning before I got up. Then we gave him his medicine in some canned food after I got up. He used to eat at least 3 times a day, but with the medicine in the food, he won't eat it. And he hasn't had anything else, since Friday morning, & it's late Saturday night now. I thought he would get hungry enough to eat, but not ! I don't want him to get outside till he eats either, so he won't eat at his owner's house, or anywhere else. I hate to waste $6.50 worth of medicine, too. So, he may get more hungry before it's all over. I'm doing this to get him better, not to hurt him or punish him, but he probably doesn't know that. Or care - he just wants something better to eat. So he has sat in here looking out the door wanting out a lot the last 2 days. He cries a little bit, but not too loud. I just have to stay tougher than him, & not give in. How long is this gonna take ?? Oliver, just eat your food, please............