Main objective: To assess the effectiveness, using evidence from randomised trials, and the association, using evidence from nonrandomised studies, of pharmaceutical industry promotional interactions with prescribers (including receipt of information, payments, gifts and samples), compared to no interactions, on the quality, quantity, cost of prescribed medicines, and on formulary requests.

Secondary objectives: To assess whether the effectiveness and association of promotional interactions with the quality, quantity and cost of prescribing differ according to the type of interaction, extent of interaction or exposure level, prescriber type, whether clinicians are trainees or licensed, gender, number of years in practice, prescriber attitude to promotional information and whether the promotional interactions occur in high, middle or low-income settings, according to World Bank classifications of gross national income per capita (World Bank 2018). We will explore whether these listed factors are effect modifiers. Another secondary objective is to assess the effects of prescriptions stimulated by pharmaceutical industry promotional interactions with prescribers on clinical patient outcomes.