Block buster drugs share a variety of common features, among which is the tendency to create entirely new markets. For example, an early "informed" estimate of the potential market size for the hypothetically "perfect" peptic ulcer drug was thirty-five million dollars. Based on current sales, however, we reckon this hypothesis to have underestimated the actual market demand for omeprazole (Prilosec) by about 400-fold. Similarly, prior to the introduction of the "retired" block busters chlordiazepoxide and diazepam (Librium and Valium), the market for "minor tranquilizers" in the treatment of anxiety and neurosis did not exist. Thus, once an emerging block buster seems to be therapeutically working, it is not unusual for diagnostic rates of the disease for which it is indicated and efficacious to actually increase. Top block buster drugs generally have or appear to have a high margin of safety.