Nierfunctieverlies gerelateerd aan staken hartmedicatie postmyocardinfarct
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Poorer kidney function predicts worse long-term adherence to heart medications after myocardial infarction atop older adults' already low overall adherence, researchers found.
Nonadherence to statins, ACE inhibitors or angiotensin receptor blockers (ARBs), and beta-blockers reached 45% to 55% by 36 months post-MI among seniors overall in a cohort study by Wolfgang C. Winkelmayer, MD, ScD, of Stanford University in Palo Alto, Calif., and colleagues.
The figures were significantly worse for ACE/ARB and beta-blocker adherence with kidney dysfunction (P=0.05 and P=0.005 for interaction with estimated glomerular filtration rate over time), they reported online in the Clinical Journal of the American Society of Nephrology.
"The results of our analysis have important clinical implications because elderly patients with kidney dysfunction are at high risk for cardiovascular mortality and may therefore benefit the most from dedicated interventions aimed at improving long-term medication adherence," they wrote in the paper. Out-of-pocket costs were unlikely to have been a factor, the researchers noted, since all patients in the study were in a program that paid for prescriptions with only small copayments.
Pill burden overload may be a more likely explanation, they suggested. Prior studies have shown that chronic kidney disease patients average eight prescriptions, with some patients taking as many as 24 different drugs multiple times daily.
The higher rates of functional limitations, cognitive impairment, and depression seen among chronic kidney disease patients may also predispose them to lower medication adherence, Winkelmayer's group noted. But physicians should be alert to prescribing all appropriate medications and monitoring nonadherence in this high-risk group, he agreed with the researchers.
The researchers studied medication compliance in a cohort of 2,103 Medicare beneficiaries enrolled in a low-income pharmacy benefits assistance program in Pennsylvania after hospital discharge for MI.
Renal function was assessed using the first serum creatinine after hospitalization and expressed as estimated GFR.
In the first 90 days after their hospitalization, just 49% of the patients filled a prescription for an ACE inhibitor or ARB, 45% for a beta-blocker, and 29% for a statin. Pharmacy refill data in three-month intervals over 36 months of follow-up showed a steady drop in the percentage of days covered by a prescription.
At baseline, about 70% of patients were considered adherent, with prescriptions covering at least 80% of days in each of the three medication classes. Nonadherence rose to 35% to 40% by 12 months, and to 40% to 48% at 24 months.
By 36 months, the mean percentage of days covered dropped to 50% to 60% for all three drug classes, and only about half of patients remained adherent. For ACE inhibitors and ARBS, the decline was steepest among patients in the lowest estimated glomerular filtration rate group with an eGFR under 30 ml/min per 1.73 m2 compared with the other higher eGFR groups. For beta-blockers, the decline in adherence was faster in the two lower eGFR groups compared with those with an eGFR of at least 60 ml/min per 1.73 m2. Long-term statin adherence did not vary by baseline level of kidney function. Age, sex, and black race had no significant impact on adherence for any of the three drug classes. The researchers cautioned that the study used only a single serum creatinine measurement to determine baseline eGFR. "However, many of these patients may have had some degree of acute kidney injury in the setting of their MI, thereby underestimating the true baseline kidney function," they wrote in the paper. Also, generalizability to more racially and socioeconomically diverse populations was unclear, since the study included largely elderly white women of low income, Winkelmayer's group noted.
Another limitation was that the study used claims data as a measure of medication adherence without direct assessment of whether patients actually took their pills or whether their physicians discontinued the drugs, which did not allow for determination of reasons for nonadherence.
1. Chang et al, CJASN 2011