The back pain after drinking may be caused by the following reasons: 1. It may be caused by the exacerbation of the original inflammation induced by drinking alcohol. The back pain may be caused by the spasm of the muscles of the back, which may be caused by the influence of bad posture. 3. 4, may also be due to internal organ lesions, such as after drinking alcohol may induce patients to angina, myocardial infarction, cholecystitis, pancreatitis, a series of diseases, such diseases in the attack, may cause pain in the back related areas.