Competing interests: The BMJ has judged that there are no disqualifying financial ties to commercial companies. The authors declare the following other interests: BM is an associate editor of Drug and Therapeutics Bulletin, a BMJ journal. She is also a member of Health Action International (HAI-Europe), Association Mieux Prescrire, and the International Society of Drug Bulletins. Further details of The BMJ policy on financial interests are here: https://www.bmj.com/about-bmj/resources-authors/forms-policies-and-checklists/declaration-competing-interests