Post-approval drug risks are a significant public health problem. A central instrument to mitigate them in the European Union is direct to healthcare professional communications (DHPC), typically a letter sent from the manufacturer to prescribers. However, evaluations show that DHPCs have limited impact on prescribing behavior. Which factors influence prescribers' lack of adoption of DHPCs remains unknown. This article presents a think-aloud reading study of 17 Danish general practitioners' reading aloud a 2013 DHPC about new oral anticoagulants, interjecting their immediate reactions and associations to daily clinical routines concurrently. We found that interviewees inferred more from the DHPC than risk information. It was perceived to be commercially biased, which generally discouraged reading despite learning new safety information. DHPCs were also disregarded because they are isolated from routinely used clinical information sources. Furthermore, DHPCs were perceived as pre-emptive acts of legal defence aiming to relocate responsibility from the manufacturer onto prescribers. In conclusion, the study indicates that certain DHPCs may be disregarded because of the perceived motivations that prescribers attribute to the DHPC senders. While the specific letter itself was deemed unsatisfactory, its legitimacy among prescribers remains the central challenge. Further integration with trusted and established information structures is also needed.