The solution to one problem can be the cause of another.
Three days' worth of painkillers may not do the job.
I had unbearable back pain over a year ago. I went to the ER. It was a Friday. They fixed me up with some painkiller and the doctor gave me a prescription for enough pills to last about a day and a half. I pressed the doctor to explain how I was going to manage once the pills ran out but he just kind of didn't say anything. Fortunately I knew a doctor who was able to get me an appointment on Monday morning with a doctor who gave me a script for enough pills to buy me some time to find a way to get better. (He said I needed surgery and he would operate on me the following Tuesday. A little Web surfing made it clear just how risky this would be, and I had the very good fortune to get a suggestion from a friend for an exercise that relieved the pain.)
I was just lucky. I could not have endured another week or so of that pain.
Three days may not be enough time for an ER patient to see a doctor and either get a longer-term prescription or solve the problem that is causing the pain.