Administrative data alone are insufficient to understand equivalence of two common blood pressure drugs
Research Activities September 2011, No. 373
Both angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACE inhibitors) lower blood pressure. ARBs, the new kid on the block, are more expensive, but they do not cause the cough that ACE inhibitors users sometimes experience. A new study finds that although the drugs appear to be different in preventing some clinical events, Medicare data lack detail for determining which drug is better.
ARBs were associated with lower risk of sudden cardiac death and heart attacks. For example, the risk of sudden cardiac death was much lower (49 percent) for patients with heart failure who took ARBs than for patients taking ACE inhibitors. And those who took ARBs had a 19 to 24 percent lower risk of being hospitalized for a heart attack than patients who took ACE inhibitors.
However, characteristics of ARB and ACE inhibitor users varied, making a true comparison of the drugs' effectiveness difficult. Prescribing practices and patient preferences may be at the heart of why patient characteristics were so different. For example, doctors could have been more likely to prescribe ARBs for patients who had chronic kidney disease, potentially believing ARBs were easier on the kidneys. Further, patients who took ARBs were more likely to use preventive drugs to control their cholesterol levels or treat osteoporosis, which may mean they had better access to health care. And, because advertisements for ARBs are commonplace, savvy patients may be specifically requesting these drugs in lieu of ACE inhibitors.
The authors suggest that while Medicare data are an important resource that captures population-based real-world patients, long-term clinical outcomes, and detailed information on drug use, the absence of clinical information and behavioral characteristics may not provide an accurate picture of why a doctor or patient chose a particular drug. This study was funded in part by the Agency for Healthcare Research and Quality (HS17731 and 290-05-0016).
See "Angiotensin receptor blockers and angiotensin-converting enzyme inhibitors: Challenges in comparative effectiveness using Medicare data," by Soko Setoguchi, Sc.M., Dr.P.H., M.D., M.P.H., W.H. Shrank, M.D., M.S.H.S., J. Liu, and others in the May 2011 Clinical Pharmacology and Therapeutics 89(5), pp. 674-682.