The constant pain of butt injection may be caused by improperly selected position, high concentration of medicine, drug stimulation and other reasons. 1. Improper selection of location: When injecting in the buttocks, if the injection location is not properly selected, the sciatic nerve branch may be damaged. When the sciatic nerve branch is stimulated by the needle prick or the local high concentration of medicine, there will be a manifestation of constant pain in the buttocks after the injection. 2.. The concentration of the medicine is too high: when the concentration of the medicine is too high, part of the medicine can not be absorbed. This leads to the local formation of foreign body granuloma, resulting in the symptom of pain all the time in the buttocks after intramuscular injection. 3. Drug stimulation: some drugs will have obvious stimulation effect on the local skin, leading to local skin necrosis, thus producing the symptom of constant pain in the buttocks. It is recommended that patients who have been suffering from pain from spanking injection should go to the hospital in time to be treated symptomatically by the doctor.