David W. J. Clark

Abstract: The New Zealand Intensive Medicines Monitoring Programme (IMMP) was established in 1977 to enhance monitoring for previously unrecognised adverse drug reactions associated with selected new medicines. This involved establishing cohorts from prescription data and collection of event information: thus New Zealand was a pioneer in the development of the methodology now known as Prescription Event Monitoring (PEM). In the IMMP, PEM cohorts are established using information, supplied by pharmacies, from prescriptions for medicines that have been selected for monitoring. Events are identified subsequently from follow-up questionnaires to prescribing physicians and from other sources, including spontaneous reporting of events. The objective of this review is to illustrate how the IMMP methodology enables identification of signals of previously unrecognised adverse reactions. This is enhanced by high response rates from pharmacists and prescribers in providing prescription and event data respectively. In addition, high quality event reports are obtained from multiple sources including follow-up event returns from prescribers, reports received through the national spontaneous reporting programme, prescription returns and from record linkage to other databases. Collaboration with other national centres and with the WHO Collaborating centre for international drug monitoring in Uppsala, Sweden (WHO-UMC) enables information on cases from their databases to be used in validation of IMMP signals. The NZ IMMP methodology and signals of previously unrecognised adverse drug reactions arising from the IMMP databases are reviewed. Recent signals include amnesia and QTc prolongation with sibutramine; pain activation with sumatriptan; epistaxis with risperidone; psychiatric and visual disturbances with the COX-2 inhibitors celecoxib and rofecoxib and psoriasis with rofecoxib. In addition, other types of investigation are discussed along with the importance of rapid communication to prescribers of new information concerning the risks of medications. The IMMP has features that differ from those of other centres that incorporate PEM methodology. New Zealand is a small country (approximately 4 million) and thus communication is relatively easy. This facilitates good rapport with prescribing doctors. However, mainly because of the small population, several years may be required to achieve a large cohort. Although this has drawbacks in terms of rapid results, it enables a longitudinal approach to prescription data analysis, including aspects of prescribing such as reasons for cessation of therapy and changes in prescribing practise. Although not specifically reviewed in this article, the programme has also made significant contributions in determining the incidence of certain adverse drug reactions and in carrying out in-depth epidemiological investigations relating to the safe use of medicines. Through these activities, the New Zealand IMMP provides an ongoing contribution to safety in the use of medicines.

Polymyositis occurring in patients treated with omeprazole has been signalled as a possible adverse drug reaction (ADR) by the New Zealand Intensive Medicines Monitoring Programme (IMMP) and the WHO Collaborating Centre for International Drug Monitoring: the Uppsala Monitoring Centre (UMC). Polymyositis and other myopathies have also been reported in post-marketing data and in the medical literature in association with proton pump inhibitor (PPI) use. We wished to follow-up these signals and investigate the evidence of causality for the association of polymyositis and other myopathy with PPI use. Spontaneously reported ADRs from national monitoring centres are sent to the WHO ADR database (VigiBase). VigiBase was searched for case reports of the PPIs, omeprazole, pantoprazole, lansoprazole, esomeprazole and rabeprazole, with terms indicative of myopathy, and further information was elicited from the national centres to help establish causality. Literature sources were reviewed for the occurrence of the above terms in combination with PPIs. In total, there were 292 reports of various myopathies with PPIs, excluding 868 cases of ‘myalgia’. In this analysis, 69 patients recovered when the drug was withdrawn and, in 15 patients, the reaction re-occurred when the drug was reinstated. In one-third of the 292 cases, the PPI was the single administered drug, and the PPI was the single suspected drug by the reporter in 57% of reports where concomitant medication was used. In this analysis, three index cases are documented. One involves the same patient taking three different PPIs (lansoprazole, esomeprazole and rabeprazole) at different time periods, with myalgia and muscle weakness occurring with all three drugs. In the two other index cases, myopathies with esomeprazole and omeprazole were reported with positive rechallenge, and causality was assessed as ‘possible’ and ‘certain’ by the reporting centres. In 27 cases myositis or polymyositis was reported. Other myopathies were reported, including 35 cases with rhabdomyolysis. In 9 of these cases, the PPI was withdrawn and the reaction abated. The PPI was reinstated in one patient, but the reaction did not re-occur. Time to onset was given in 17 of the rhabdomyolysis cases, rhabdomyolysis occurred with the first week in 9 cases, and in 3 cases the reaction occurred between 14 days to 3 months of treatment. In 12 of these patients, an HMG-CoA reductase inhibitor (statin) was taken concomitantly. Case reports from the WHO ADR database, including index cases involving four out of five PPIs, along with evidence of a possible mechanism, provide compelling evidence that there is a causal association between members of the PPI drug class and myopathy including polymyositis. Evidence was also obtained to support the view that PPI use may be associated with occurrence of other myopathies, including the serious reaction rhabdomyolysis.

Aims: To investigate a possible association of sibutramine with QT interval prolongation.Methods: Post‐marketing surveillance using prescription event monitoring in the New Zealand Intensive Medicines Monitoring Programme (IMMP) identified a case of QT prolongation and associated cardiac arrest in a patient taking sibutramine for 25 days. This patient was further investigated, including genotyping for long QT syndrome. Other IMMP case reports suggesting arrhythmias associated with sibutramine were assessed and further reports were obtained from the World Health Organisation (WHO) adverse drug reactions database.Results: The index case displayed a novel mutation in a cardiac potassium channel subunit gene,KCNQ1, which is likely to prolong cardiac membrane depolarization and increase susceptibility to long QT intervals. Assessment of further IMMP reports identified five additional patients who experienced palpitations associated with syncope or presyncopal symptoms, one of whom had a QT_cat the upper limit of normal. Assessment of reports from the WHO database identified three reports of QT prolongation and one fatal case of torsade de pointes in a patient also taking cisapride.Conclusions: This case series suggests that sibutramine may be associated with QT prolongation and related dysrhythmias. Further studies are required, but in the meantime we would recommend that sibutramine should be avoided in patients with long QT syndrome and in patients taking other medicines that may prolong the QT interval.

The ability to identify individuals who are susceptible to adverse drug reactions (ADRs) has the potential to reduce the personal and population costs of drug-related morbidity. Some individuals may...

Inhibitors of the cyclo-oxygenase (COX)-2 isoenzyme were developed with the expectation that their use would be accompanied by a reduction in adverse reactions thought to be mediated through COX-1 compared with conventional nonselective NSAIDs. However, the results of some clinical studies and other evidence have led to the hypothesis that use of COX-2 inhibitors may contribute to an increased risk of adverse thromboembolic (TE) events. In this review, we have evaluated the evidence from small-scale in vitro and in vivo pharmacological studies, clinical trials and large-scale pharmacoepidemiological studies and commented on the relationship between the pharmacological characteristics related to thromboembolic events and the clinical effects in large-scale clinical trials and pharmacoepidemiological studies. Overall, the pharmacological evidence suggests that a prothrombotic effect of COX-2 selective inhibitors is plausible. To date, despite the results from the Vioxx Gastrointestinal Outcome Research (VIGOR) study from which the clinical concern regarding cardiovascular TE risk arose, the published data from other randomised controlled trials (RCTs), retrospective observational studies and spontaneous reporting schemes provide a conflicting body of evidence on the TE risk with COX-2 inhibitors. Concerns that COX-2 inhibitors may be associated with prothrombotic effects remain and these need to be addressed in large scale, RCTs designed specifically to investigate the possibility of an excess of adverse cardiovascular outcomes in users of some or all selective COX-2 inhibitors, both with and without concomitant low-dose aspirin (acetylsalicylic acid). Consideration must also be given to other pathophysiological mechanisms for potential cardiovascular risk linked with inhibition of COX-2. In view of the evidence reviewed, it is recommended that selective COX-2 inhibitors should be prescribed with caution, only in patients with conditions for which these drugs have proven efficacy and with careful monitoring of outcomes and adverse events. This is particularly important in the elderly, in patients with cardiovascular/renal disease and in patients with other risk factors that might predispose them to adverse events.

It is difficult to obtain valid estimations of the true incidence of CNS effects associated with nonsteroidal anti-inflammatory drugs (NSAIDs) from spontaneously reported adverse reactions. This is...