Short-acting opioids, like Vicodin or Percocet, get medication into your system quickly. When you take them as directed, like immediately after surgery, you probably won’t have any issues. But if you take them for too long, it may be hard to stop. Long-acting opioids, like OxyContin, give your body a smaller amount of medication over a longer time. They’re used to treat diseases that cause chronic pain, like fibromyalgia or arthritis.