Like a lot of men, male cats like to pretend they're not in pain. Neuter surgery isn't painless, however, and there's no reason your kitty should have to suffer. The trick is to give him just the right amount of pain medication to get him through the worst part.
Most veterinarians will give your cat a pain reliever injection as soon as the neuter surgery is finished. Stopping the pain before it starts is the best way to keep it under control. It also helps keep your kitty comfortable so he doesn't wake up from anesthesia in a strange place and in a lot of pain. The effects of the pain reliever usually only last a few hours, so he will need you to give him oral pain relievers if the veterinarian suggests them.
Age and Health
Some cats are just tougher than others. How much pain they can tolerate, or how much pain they will be in after surgery, can depend on their age, health and physical condition. Kittens under 6 months old will probably need some sort of pain medication, as well as senior cats over 8 years old. If you have a healthy, young adult cat he might not need any pain medication, or only for the first few hours after being neutered.
One of the trickiest parts of caring for your cat right after he's been neutered is making sure he isn't in serious pain, but that the surgery site is just tender enough that he will be careful not to hurt himself. If kitty feels too good he could rip open the incision or pull the muscles apart while playing, jumping and running. He certainly doesn't need to be hunched up or crying in pain, but should have just enough sensitivity to be careful how he moves when he stretches and plays. Try to use the least amount of pain medication possible to keep the serious pain at bay.
Older cats and young kittens are usually more sensitive to pain and will probably need regular doses of pain medication for a longer time after neuter surgery. If there were complications during surgery, such as a testicle that didn't descend, the site will be more painful and more pain medication will be needed. Follow your veterinarian's advice, especially if neuter surgery was more complicated than usual.
Trying to relieve pain with certain over-the-counter medicines, like acetaminophen, is not only far more dangerous than the pain, it can be fatal. Don't kill your cat with kindness trying to relieve his pain. Give only medications approved or prescribed by your veterinarian and only in the amounts and for the length of time suggested. In most cases, your cat will only need pain management for 24 to 48 hours after surgery. If he is still in severe pain after the first 48 hours and there were no complications during surgery, contact your veterinarian.