Person: Walker, Alexander
Loading...
Email Address
AA Acceptance Date
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
Walker
First Name
Alexander
Name
Walker, Alexander
4 results
Search Results
Now showing 1 - 4 of 4
Publication Active safety monitoring of newly marketed medications in a distributed data network: application of a semi-automated monitoring system(2014) Gagne, Joshua; Glynn, Robert; Rassen, Jeremy; Walker, Alexander; Daniel, Gregory W.; Sridhar, Gayathri; Schneeweiss, SebastianWe developed a semi-automated active monitoring system that uses sequential matched-cohort analyses to assess drug safety across a distributed network of longitudinal electronic healthcare data. In a retrospective analysis, we showed that the system would have identified cerivastatin-induced rhabdomyolysis. In this study, we evaluated whether the system would generate alerts for three drug-outcome pairs: rosuvastatin and rhabdomyolysis (known null association), rosuvastatin and diabetes mellitus, and telithromycin and hepatotoxicity (two examples for which alerting would be questionable). During >5 years of monitoring, rate differences (RDs) comparing rosuvastatin to atorvastatin were -0.1 cases of rhabdomyolysis per 1,000 person-years (95% CI, -0.4, 0.1) and -2.2 diabetes cases per 1,000 person-years (95% CI, -6.0, 1.6). The RD for hepatotoxicity comparing telithromycin to azithromycin was 0.3 cases per 1,000 person-years (95% CI, -0.5, 1.0). In a setting in which false positivity is a major concern, the system did not generate alerts for three drug-outcome pairs.Publication Benzodiazepine Use and Hip Fractures in the Elderly(American Medical Association (AMA), 2004) Wagner, Anita; Zhang, Fang; Soumerai, Stephen; Walker, Alexander; Gurwitz, Jerry H.; Glynn, Robert; Ross-Degnan, DennisPublication Outcomes of Reference Pricing for Angiotensin-Converting–Enzyme Inhibitors(New England Journal of Medicine (NEJM/MMS), 2002) Schneeweiss, Sebastian; Walker, Alexander; Glynn, Robert; Maclure, Malcolm; Dormuth, Colin; Soumerai, StephenBackground In January 1997, reference pricing for angiotensin-converting–enzyme (ACE) inhibitors for patients 65 years of age or older was introduced in British Columbia, Canada. For medications within a specific class, insurance covers the cost up to the reference price, and patients pay the extra cost of more expensive medications. Although reference pricing may reduce the costs of prescription drugs, there is concern that patients may switch to less effective medications or stop treatment. Methods We analyzed data from the Ministry of Health on all 37,362 residents of British Columbia who were 65 or older and were enrolled in the provincial health insurance program, received ACE inhibitors priced higher than the reference price of $27 a month in 1996, and were potentially affected by the new policy. We identified 5353 residents who switched to an ACE inhibitor not subject to cost sharing during the first six months and compared them with 27,938 residents who received only ACE inhibitors subject to cost sharing. Results Reference pricing for ACE inhibitors was not associated with changes in the rates of visits to physicians, hospitalizations, admissions to long-term care facilities, or mortality. The probability of stopping antihypertensive therapy decreased as compared with the probability before the change in policy (relative risk, 0.76; 95 percent confidence interval, 0.65 to 0.89). Eighteen percent of patients who had been prescribed ACE inhibitors subject to cost sharing switched to low- er-priced alternatives. As compared with patients who did not switch, those who did had a moderate transitory increase in the rates of visits to physicians (rate ratio, 1.11; 95 percent confidence interval, 1.07 to 1.15) and hospital admissions through the emergency room (rate ratio, 1.19; 95 percent confidence interval, 0.99 to 1.42) during the two months after switching, but not subsequently. Conclusions We found little evidence that when reference pricing for ACE inhibitors was introduced in British Columbia, patients stopped treatment for hypertension or that health care utilization and costs increased.Publication The Zelnorm Epidemiologic Study (ZEST): A Cohort Study Evaluating Incidence of Abdominal and Pelvic Surgery Related to Tegaserod Treatment(BioMed Central, 2012) Seeger, John; Quinn, Sherry; Earnest, David L; Lembo, Anthony; Kuo, Braden; Rivero, Elena; Walker, AlexanderBackground: Pre-marketing clinical studies of tegaserod suggested an increased risk of abdominal surgery, particularly cholecystectomy. We sought to quantify the association between tegaserod use and the occurrence of abdominal or pelvic surgery, including cholecystectomy. Methods: This cohort study was conducted within an insured population. Tegaserod initiators and similar persons who did not initiate tegaserod were followed for up to six months for the occurrence of abdominal or pelvic surgery. Surgical procedures were identified from health insurance claims validated by review of medical records. The incidence of confirmed outcomes was compared using both as-matched and as-treated analyses. Results: Among 2,762 tegaserod initiators, there were 94 abdominal or pelvic surgeries (36 gallbladder): among 2,762 comparators there were 134 abdominal or pelvic surgeries (37 gallbladder) (hazard ratio HR] = 0.70, 95% confidence interval [C.I.] = 0.54-0.91 overall, HR = 0.98, 95% C.I. = 0.62-1.55 for gallbladder). Current tegaserod exposure compared to nonexposure was associated with a rate ratio [RR] of 0.68 (95% C.I. = 0.48-0.95) overall, while the RR was 0.99 (95% C.I. = 0.56-1.77) for gallbladder surgery. Conclusions: In this study, tegaserod use was not found to increase the risk of abdominal or pelvic surgery nor the specific subset of gallbladder surgery.