ABSTRACT
Since patients may report spontaneously adverse events associated with their medications, such notifications are constantly on the rise. In 2017, an unexpected rise of notifications associated with the marketing of a new formula of Levothyrox, differing from the 30-year-old drug only by minor elements, occurred in France amidst widespread media coverage. Not much, if any, scientific or pharmacological rationale was identified to explain that signal. This led us to focus on the profile and the clinical characteristics of these notifications and compare them to those associated with other drugs. We gathered all the spontaneous drug adverse event notifications associated with either Levothyrox® or other drugs, that we received from patients in 2017, in the sanitary territory of ~2.3 M people we surveyed. Each notification was assessed by a multidisciplinary team. We compared the number of notifications, the number of symptoms described and their clinical characteristics. A total of 1 544 patient notifications were evaluated: 1 372 cases totaling 7 342 adverse events concerned Levothyrox® new formula, as compared with 172 cases reporting 528 adverse events for all other drugs. The number of symptoms reported per notification was significantly higher for Levothyrox® (5.4) than for other drugs (3.1, P < 0.001). Symptoms associated with Levothyrox® belonged to more System Organ Classes and were often unrelated to the disease or treatment, as compared with those associated with other drugs. The distribution of the cases according to the number of symptoms described was starkly different, the Levothyrox® distribution being unimodal. Health authorities must address this issue as such large atypical reporting disproportionally affects the European pharmacovigilance database.
