Don't give your cat any of your medications. While it may be the same drug, it may have inactive ingredients that are harmful to cats. Many inactive additives/pill binders/liquids that are used in medications for humans could be toxic to cats. Cats metabolize foreign substances differently than humans due to differences in their digestive system and liver. The same is true of dogs and other pets as well, but cats are particularly vulnerable to poisoning according to everything I have read. In fact, you should even carefully research cleaners that you use to clean surfaces in your home because of the danger of your cat being poisoned by licking or sniffing a surface. Cats are that sensitive to all foreign substances and all medications must be administered very carefully and under veterinary supervision.
I feel very bad for your cat, and I can certainly understand how you feel. Just showing him/her love and affection and giving your cat reassurance will make your cat feel a lot better. If you have any other cat questions, I have found that a website called The Cat Site is an excellent resource.