Many hemodialysis patients face a high pill burden and fail to take all of their prescribed phosphate binder medication, a new study finds.
To the degree that phosphate binder therapy reduces cardiovascular risk and bone disease, which is not yet proven, suboptimal medication compliance might harm patient health. This study found higher serum phosphorus levels among non-adherent dialysis patients.
Using data from the Dialysis Outcomes and Practice Patterns Study (DOPPS), Rachel B. Fissell, MD, of Vanderbilt University Medical Center in Nashville, and colleagues assessed associations between phosphate binders, medication non-adherence, and levels of serum phosphorus and parathyroid hormone (PTH) in 5,262 in-center hemodialysis patients from 12 countries.
According to results published online in Hemodialysis International, prescriptions for phosphate binders ranged from an average 7.4 pills per day in the United States to 3.9 in France. Half of patients were prescribed 6 or more pills per day and 13% at least 12 pills.
Patients were asked by questionnaire at DOPPS entry how many times they skipped phosphate binders in the prior month. Nearly half (45%) reported skipping the medication at least once, including 57% of patients in the United States. The investigators observed a trend toward greater non-adherence and higher amounts of daily pills.
Medication non-adherence (defined as skipping medication 3 or more times in a month) was associated with high serum phosphorus levels above 5.5 mg/dl as well as elevated parathyroid hormone levels above 600 pg/ml. Poor adherence was highest in the U.S. at 24% and lowest in Belgium, Japan, Germany, and Spain at 12% each. Unmarried patients and those with mental health problems were more likely to be non-adherent.
More than half of patients (55%) reported taking all of their medication. These patients were more likely to be married or living with family, indicating family support. Half also saw their physicians 2–3 times a week (compared with just 1 in 3 patients with poor medication adherence), ostensibly providing opportunities to reinforce medication regimens.
“Simpler, more achievable [phosphate binder] PB regimens could lead to better adherence and perhaps lower phosphorus and PTH levels,” the investigators suggested. “For patients with high [serum phosphorus], it may be more effective to first assess what pills patients are actually taking and make efforts to reduce the pill number, before increasing the PB prescription.” Adjusting medications to actual patient behavior might also save money.
Since this was an observational study, it has some expected limitations. It remains important to assess other causes of excess phosphorus, such as from diet, inadequate dialysis time, and increased bone resorption, the researchers noted.