The reaction upon sudden and prolonged abstinence from heroin after a dependency has developed. Symptoms include (a) drowsiness for several hours, (b) restlessness, yawning, profuse sweating, running nose and eyes, feelings of anxiety, insomnia, and muscular aches, (c) after 24 h, gooseflesh, uncontrolled muscular twitching, vomiting, diarrhea, muscular aches, a rise in body temperature, dehydration, and an increase in systolic blood pressure. These symptoms then gradually subside within 72 h.