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Spontaneous reporting of adverse drug reactions (ADRs) is a cornerstone in pharmacovigilance. However, information about the underlying consumption of drugs is rarely used when analysing spontaneous reports. The purpose of this study was to combine ADR reports with drug consumption data to demonstrate the additional information this gives in various scenarios, comparing different drugs, gender-stratified sub-populations and changes in reporting over time. We combined all Norwegian ADR reports in 2004–2013 from the EudraVigilance database (n = 14.028) with dispensing data from the Norwegian Prescription Database (more than 800 million dispensed prescriptions during 2004–2013). This was done in order to calculate drug-specific consumption-adjusted adverse drug reaction reporting rates (CADRRs) by dividing the number of reports for each drug with the number of users of the drug during the same time period. Among the ten drugs with the highest number of ADR reports and the ten drugs with the highest CADRR, only four drugs were in both categories. This indicates that drugs with a high number of reports often also have a high number of users and that CADRR captures drugs with potentially relevant safety issues but a smaller number of users. Comparing reported ADRs in females and males using methylphenidate, we found that the two groups report different ADRs. Finally, we showed that changes in ADR reporting for simvastatin and atorvastatin during 2004–2013 were due to changes in consumption and that atorvastatin had a higher CADRR but fewer reports than simvastatin. CADRR provides additional information compared with number of reports alone in studies using spontaneous reports. It is important for researchers to adjust for consumption whenever possible in pharmacovigilance studies.

Background Since 1 March 2010, patients in Norway have had the opportunity to report adverse reactions to The Norwegian Medicines Agency. The purpose of this study was to review these reports. Material and method The content of adverse reaction reports received from patients in the period from 1 March 2010 to 31 December 2013 was classified based on age, gender, suspected drug and suspected adverse reactions. The patient reports were compared to the adverse reaction reports received from health care professionals in the same period. Results A total of 755 reports from patients and 9629 reports from health care professionals were received during the period in question. The 20-39-year age group was most frequently represented in the patient reports. In the reports from health care professionals, the main age group was 0-9 years, followed by the 60-69-year age group. The drug group most often mentioned in the patient reports was drugs acting on the nervous system, and above all psychotropic drugs and analgesics, while vaccines dominated in the reports from health care professionals. Adverse mental and neurological reactions were most frequently reported by patients, while general symptoms and local reactions were most common in the reports from health care professionals. A total of 74 different adverse reactions were reported only by patients and not by the health care professionals. Interpretation Adverse drug reaction reports from patients are different from reports by health care professionals. Our findings indicate that the system with patient reporting functions as a supplement to reporting from health care professionals.