Atrial fibrillation (AFib) is an increasingly common and potentially life-threatening heart rhythm abnormality that is treated with a combination of drugs to slow and normalize the heart rhythm and anticoagulants to prevent formation of blood clots.
The calcium channel blocker diltiazem, sold under the brand name Cardizem among others, is a drug commonly used to slow the heart rate and reduce arrhythmia symptoms during AFib, along with beta-blockers such as metoprolol.
Diltiazem is preferred for AFib patients with hypertension and chronic obstructive pulmonary disease (COPD), but it interacts with anticoagulant drugs to reduce the rate at which they are removed from the body, which could increase bleeding complications.
In a national retrospective study led by researchers at Vanderbilt University School of Medicine, diltiazem, when given in combination with the anticoagulant drugs apixaban (Eliquis) or rivaroxaban (Xarelto), significantly increased the risk of serious bleeding compared to metoprolol.
This could have important clinical consequences for millions of patients, the researchers reported April 15 in the Journal of the American Medical Association. Therapeutic drug monitoring, to minimize the risk of bleeding, may be indicated for patients on diltiazem, the researchers concluded.
As many as 6 million people in the United States have AFib, which increases the risk of stroke, dementia, and heart failure, and nearly doubles the risk of death.
The estimated cost of treating the disorder and its complications exceeds $25 billion a year. That’s just the beginning, as the number of AFib cases is expected to double by 2030.
The current national cohort study looked retrospectively at 204,155 Medicare beneficiaries with AFib, age 65 years and older, who were taking apixaban or rivaroxaban to prevent blood clots and who also had begun treatment with diltiazem or metoprolol to control heart rate.
Compared to metoprolol, treatment with diltiazem, especially at higher doses, was associated with a significantly increased risk of serious bleeding that required hospitalization or resulted in death.
Patients at high risk of bleeding complications include the elderly, and those who have a history of bleeding, or who take medications that by themselves increase bleeding risk, and they should be monitored carefully while on diltiazem, the researchers cautioned.
Wayne Ray, PhD, professor of Health Policy in the Vanderbilt University School of Medicine, is the paper’s corresponding author.
Other Vanderbilt co-authors are William Dupont, PhD, and James Daugherty, MS (Department of Health Policy); and Walter Smalley, MD, MPH, C. Michael Stein, MB, ChB, Adriana Hung, MD, MPH, Alyson Dickson, MA, and Katherine Murray, MD (Department of Medicine, Vanderbilt University Medical Center).
This study was supported by National Institutes of Health grant 5R01HL151523.