Challenge of phosphorus control in hemodialysis patients: a problem of adherence?

Objective: Few studies have investigated nonadherence to phosphate binders. The aim of this study was to evaluate the degree of adherence of our hemodialysis (HD) patients to phosphate binders and to determine which variables were related to nonadherence to treatment. Methods: In 165 HD patients, the degree of adherence to the drugs prescribed was studied using the Simplified Medication Adherence Questionnaire. Results: Of patients, 40% were nonadherent. Specific nonadherence to phosphate binder and hypotensive medication was admitted by 21% and 13% of patients, respectively. Nonadherent patients had significantly higher mean serum phosphorus (P) (4.7 +/- 0.9 mg/dL vs. 4.4 +/- 0.7 mg/dL; p=0.007) and potassium levels (6.3 +/- 4.4 mEq/L vs. 5.3 +/- 1.4 mEq/L; p=0.04). There was a statistically significant association between mean P levels >5.5 mg/dL in the last 6 months and nonadherence to treatment (X-2=4.8; 95% confidence interval [95% CI], 1.0-6.6; p=0.02). No relationship was found between patients with blood pressure levels >140/90 mm Hg and nonadherence to hypotensive medication (X-2=0.02; 95% CI, 0.2-4.1; p=0.88). Patients specifically nonadherent to phosphate binders were more likely to have P levels >5.5 mg/dL (X-2=4.7; 95% CI, 1.07-6.5; p=0.03). No statistically significant association was found between patients noncompliant with hypotensive agents and those noncompliant with phosphate binders (X-2=0.39; 95% CI, 0.4-4.7; p=0.53). There were no significant differences between adherent and nonadherent patients in terms of age, time on hemodialysis, Charlson Comorbidity Index, number of drugs prescribed and number of tablets per day (p>0.05). Conclusion: Nonadherence to pharmacological treatment in dialysis patients is high. Nonadherence to phosphate binders was greater than for hypotensive agents, did not coexist in the same patients and had a greater impact on target achievement.