The monitoring of drug safety to identify potential adverse drug reactions (ADRs) as early as possible to keep the number of affected individuals to a minimum has been a public health concern since the thalidomide tragedy at the beginning of the 1960s. At the national level, the typical postmarketing surveillance method is the voluntary reporting system, the success of which has commonly depended on the dedication of individuals managing them and constant efforts to remind health professionals to use the system. Other methodologies using hospitalized patients have been developed, but these have often been designed to focus on specific ADRs rather than to monitor all ADRs. Although some voluntary reporting systems have achieved valuable successes , they are not infallible, and more systematic methods have been proposed either to replace them or, more often, to enhance them. Canada’s passive ADR voluntary reporting system has several limitations , and it is crucial that active signalling schemes be developed to augment it. buy ortho tri-cyclen online
Few schemes have moved beyond the proposal stage, although one (prescription-event monitoring [PEM] in the United Kingdom ) has achieved some success. However, PEM and voluntary reporting systems are both passive methods that rely on information being supplied to them by busy health professionals whose main interests and concerns are directed elsewhere, and, thus, suffer from a lack of response. Most voluntary reporting systems are thought to underestimate the incidence of ADRs by a wide margin . PEM has a substantial nonresponse rate to its questionnaires (about 45% ), and the validity of some of its information may be questioned because it is not known whether the patients for whom no response is received are different from those for whom one is obtained.