Painkillers are roughly divided into three categories of anti-inflammatory analgesics. The biggest side effect is gastrointestinal tract irritation, for example, some people have gastric ulcers themselves, after taking these drugs, especially for a longer period of time, do not pay attention to the gastrointestinal tract protection, may cause gastric ulcers. There are also some older people who use non-steroidal drugs, such as themselves have high blood pressure, may cause high blood pressure is difficult to control or poor control. The most common side effects of opioid painkillers are nausea and vomiting, which are very unpleasant to take and cause intense gastrointestinal irritation. Strong opioid painkillers are the third order, the strongest analgesic, and are usually used for cancer pain or very severe pain. Most of the side effects of these drugs are nausea, dizziness, and constipation.