Cats have a superior sense of smell. Something as acrid as citrus is enough to make a cat wince and shake its head and sneeze. Leave the cat carrier out all day long. Put a blanket in it and a few food treats. If it works, you can't knock it.
Modern drugs have minimal or no organ toxicity.
I take aspirin for a headache, and when necessary I prescribe a drug to an animal. This is actually life-saving medication. Failing to use the litter box is one of the most common reasons for a cat to be brought to a shelter. It's amazing what is the final straw for some people.