Depends on where you draw the line for "drug". Of the top of my head, some population-wide (or nearly so) public health efforts that we consider effective: fluoride in the water, iodized salt, and baby aspirin for older people. There are probably some vitamin supplements that would do a lot of good if most people took them.
Summary of the linked article: (1) We should reevaluate the benefits/harms of fluoridated water as a public health intervention. (2) The studies used to justify it in the past were flawed, especially by not accounting for a huge improvement in other dental health habits across the world. (3) Fluoride provides no additional benefits when consumed (it's just meant to affect tooth enamel), which means consuming it is inefficient and increases the risk of harm (bone weakening, nerve and brain cell damage).
