It takes about 20 minutes after taking painkillers for them to be effective. After painkillers are taken into the stomach, they first need to be digested and absorbed by the stomach, and it takes about 20 minutes for them to have an effect. Commonly used painkillers include non-steroidal analgesic and anti-inflammatory drugs, as well as opioid anti-inflammatory drugs, including fenpropidol, parecoxib, celecoxib, as well as tramadol, dizocin, pethidine, and others. When abdominal pain occurs after surgery, incisional pain is usually considered very likely, so oral non-steroidal anti-inflammatory drugs can be taken for analgesia, including fenpropidol and celecoxib. If you still can not achieve the effect of analgesia, you can also take opioid analgesics, the analgesic effect is relatively stronger.