Drugs are first tested in clinical trials to assess their safety and effectiveness before being approved for sale. However, not all side effects caused by drugs — adverse drug reactions (ADRs) — are identified in clinical trials. Indeed, in one study, a large proportion of ADRs was not detected before drugs were approved for sale.
The limitations of clinical trials to detect all serious ADRs has made clear the need for effective systems to confirm and extend the data captured in clinical trials with approved drugs. Such a system in which side effects are monitored after a drug has been licensed is called post-marketing surveillance. Because drugs used to treat HIV/AIDS have often been placed on the fast-track for approval, perhaps it is not surprising that the flip-side of this process may be that more side effects are noted once drugs are approved.
Health authorities in Western Europe and North America have different ways of conducting post-marketing surveillance. One aspect of such a system can involve patients who, upon developing ADRs, document and report them. To date, most studies on ADRs apparently do not directly involve reporting from patients to regulatory authorities.
Rearchers in Scotland conducted a study designed to develop a method for patients to report symptoms that they believe were caused by a prescribed drug. Although none of the drugs in the study are used to treat HIV infection, it may be useful reading for regulatory authorities who are interested in improving the current system for capturing data on ADRs. The researchers also checked patients' medical records to compare symptoms recorded by the their physicians. According to the researchers, their results suggest that "patients do not report all symptoms they suspect to be ADRs to their general practitioner (GPs) and GPs do not record all symptoms which may be reported to them."
Study details
Standard questionnaires were developed to help capture and classify information about ADRs. The questionnaires were tested in a pilot study and validated. Primary care doctors were contacted and about 2,300 of their patients were enrolled in this study. The drugs that patients were questioned about included four antidepressants, three anti-seizure drugs and two others used for pain relief.
Results
Researchers obtained a response rate of about 36% to their questionnaire. Most respondents were female (66%) and their average age was 51 years old. Half of respondents stated that they were taking between two and four prescribed medicines.
In reviewing 310 medical records and the completed questionnaires, researchers found that in 70% of cases the drug(s) that patients stated they were taking was not recorded in their charts. Other results were as follows:
The researchers concluded that "patients are most likely to report genuine symptoms which have a high probability of being drug-related." Moreover, they added that "patient reports of ADRs may be of value for post-marketing surveillance since the symptoms reported were seldom unattributable to drug therapy."
REFERENCES
1. Moore TJ, Psaty BM and Furberg CD. Time to act on drug safety. Journal of the American Medical Association 1998;279(19):1571-1573.
2. Lasser KE, Alen PD, Woolhandler SJ, et al. Timing of new black box warnings and withdrawals for prescription medications. Journal of the American Medical Association 2002;287;2215-2220.
3. Jarernsiripornkul N, Krska J, Capps PAG, et al. Patient reporting of potential adverse drug reactions: a methodological study. British Journal of Clinical Pharmacology 2002;53 (3):318-325.
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