Patient reporting of adverse drug reactions: useful information for pain management?

Patients' perceptions of adverse effects caused by the medicines they are prescribed may influence how they use these medicines. Little is known about patients' perceptions of the adverse effects of specific drugs in everyday use and whether these differ from those identified by clinical trials and standard post-marketing surveillance methods.

To compare reports of perceived adverse drug reactions (ADRs) obtained directly from patients taking tramadol to those found in clinical trials and two methods of post-marketing surveillance.

Postal questionnaire distributed to 1048 patients who had a prescription for tramadol dispensed over a 3-month period.

Most (84%) of the 344 respondents reported at least one symptom perceived as an ADR to tramadol. Dry mouth, light-headedness and constipation were most commonly reported. Almost half (48%) rated their most bothersome symptom as at least moderate and 43% claimed to have reported symptoms to their doctor. Perceived problems had led 38 respondents to stop taking tramadol. The 10 most frequently reported symptoms were all previously reported ADRs to tramadol. Although relatively minor, all 10 also appeared in reports to the UK Committee on the Safety of Medicines (CSM) and in prescription event monitoring. For many symptoms, the estimated range of frequency was in line with published reports, but considerably higher than that of post-marketing surveillance methods.

Symptoms were reported by the majority of respondents and for many symptoms the frequency was high. Many patients did not report symptoms they perceived to be adverse effects to their doctor. The results indicate that patient perceptions of potential ADRs are relevant and should be an integral part of a pain management strategy.