Chlorpromazine (Thorazine) was originally used to improve anesthesia’s effects for surgery; a doctor observed that when it was administered to schizophrenic patients, they stopped hallucinating as much. Sildenafil (Viagra) was originally developed to treat high blood pressure and coronary heart disease; then an unexpected side effect was observed that turned the little blue pill into one of the most popular (and profitable) drugs in history.
