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ABSTRACT Purpose To determine the validity of sequence symmetry analysis (SSA) method to detect adverse drug reactions from an administrative claims database. Methods Published randomised controlled trials (RCTs) of 19 medicines were identified through search databases, product information (PI) or the US Food and Drug Administration Web site. All adverse events (AEs) in the RCTs and the PI for the medicines were extracted. AEs were considered 'gold standard positive events' if they were reported as being statistically significant events in adequately powered RCTs. The remaining AEs were considered 'gold standard negative events' if the event was not listed as an AE in the PI for that medicine or any other medicine in its class. Indicators of AEs were identified by consensus from two clinical researchers. SSA was run for each medicine-indicator pair using four different time windows: 3, 6, 9 and 12 months. Results A total of 120 randomised placebo controlled trials were reviewed for the 19 tested medicines. A total of 165 medicine-indicator pairs (44 positive and 121 negative events) were identified and tested by SSA. At the 12-month time window, the sensitivity, specificity, positive and negative predictive values of SSA were 61% (95%CI 0.46-0.74), 93% (95%CI 0.87-0.96), 77% (95%CI 0.61-0.88) and 87% (95%CI 0.80-0.92), respectively. Using a 3-month time window, the SSA had a lower sensitivity (52%). Conclusions The SSA technique was found to have moderate sensitivity and high specificity for detecting ADRs. These results suggest that SSA is a potential tool for detecting ADRs using administrative claims data that could complement existing pharmacosurveillance methods. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Up to 21% of adverse drug event related hospital admissions are due to drug interactions. Clinical significance of drug interactions varies. • Studies which only identified drug interactions of potentially major clinical significance found lower prevalence, of between 2 and 16%. • Prevalence of drug interactions defined ‘potentially hazardous’ has had limited study, with no publications identified for the Australian population. WHAT THIS STUDY ADDS • In the study population of 287 074, 1.5% of subjects were dispensed potentially hazardous interacting drug pairs. • However, limited to populations on specific medicines, it was found that for patients dispensed verapamil, methotrexate, amiodarone, lithium, warfarin, cyclosporin and itraconazole, potentially hazardous interactions occurred at a rate greater than 5%. • These patients should be the focus of medication review programmes to avoid potentially serious adverse drug events. BACKGROUND Up to 21% of adverse drug event-related hospital admissions are due to drug interactions. Clinical significance of drug interactions varies, and drug interactions defined ‘potentially hazardous’ are more likely to contribute to morbidity and mortality. AIM The aim of this study was to assess the prevalence of potentially hazardous drug interactions in an elderly Australian veteran population. METHODS This study assessed the prevalence of potentially hazardous drug interactions, where hazardous was defined in three or more international drug interaction references, using Repatriation Pharmaceutical Benefits Scheme pharmacy claims data. Analysis was limited to patients who received regular concurrent dispensings of potentially hazardous interacting medicines. RESULTS Of the 287 074 subjects included in the study, 1.5% were dispensed potentially hazardous interacting drug pairs. For patients dispensed cyclosporin, concomitant use of a statin was common (47%); as was statin use with those dispensed itraconazole (31%). Of those dispensed methotrexate, 24% also received a non-steroidal anti-inflammatory drug; of those on lithium, 18% also received an ACE inhibitor or angiotensin 2 receptor blocker; of those on warfarin, 7.2% and 5.9% were co-dispensed an non-steroidal anti-inflammatory drugs or antiplatelets respectively; for those on verapamil, 5.3% were co-dispensed a beta-blocker, while for those on amiodarone 6.2% were co-dispensed digoxin. CONCLUSIONS Overall prevalence of potentially serious drug interactions appears to be low in the Australian veteran population. However, patients taking cyclosporine, itraconazole, methotrexate, lithium, warfarin, verapamil and amiodarone appear to be most at risk and their medicine use should be regularly reviewed to prevent potentially hazardous drug interactions. [ABSTRACT FROM AUTHOR]

Purpose To determine the number of times patients have brand and generic products substituted under Australia's Pharmaceutical Benefits Scheme (PBS) brand substitution policy. Methods A retrospective cohort study was conducted using Repatriation Pharmaceutical Benefits Scheme (RPBS) pharmacy claims data. Department of Veterans' Affairs (DVA) treatment card holders with at least two dispensings of atenolol, citalopram, enalapril, metformin, omeprazole or ramipril between 1 January 2001 and 28 February 2006 were included. Patients were followed from first dispensing until death, cessation or study end. The main outcome measure was the number of substitutions per patient during follow-up. Based on this, patients were defined as non-switchers, brand substitution or multiple switchers. Results Data for 160 145 patients were analysed. Overall more than 80% of patients either had no switches or demonstrated brand substitution. For all study drugs, patients were more likely to be non-switchers than have a brand substitution (RR range 2.6-9.4, p < 0.0001) and were more likely to be non-switchers than multiple switchers (RR range 3.2-35.9, p < 0.0001). Patients who switched were more likely to have a brand substitution than multiple switches (RR range 1.2-3.8, p < 0.0001). Multivariate logistic regression showed greater odds of being a multiple switcher with increasing number of prescribers and dispensing pharmacies, and increasing length of follow-up. Conclusions Most patients in this study did not substitute products, and those who did were more likely to demonstrate brand substitution than have multiple switches. These results suggest that the brand substitution policy is having its intended effect for most patients. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]