Purpose: To reduce the high recurrence rate of nephrolithiasis, patients are routinely prescribed secondary chemoprevention therapy with alkali citrate (Alkasolve®; Sam-On Ltd) for uric acid stones and hypocitraturia or hydrochlorthiazide (Disothiazide®; Dexcel Ltd) for hypercalciuria. However, data on adherence to these regimens are limited. The aim of this study was to assess rates of long-term adherence to alkali citrate and hydrochlorothiazide and reasons for nonadherence. Materials and Methods: Patients on follow-up for kidney stone disease at a dedicated tertiary stone clinic, from 2010 to 2016, were asked to complete a telephone survey on adherence to secondary prevention medications and reasons for nonadherence. Compliance was also verified by actual drug distribution as reported through a computerized monitoring system. Results: The cohort included 356 patients with mean age of 58 years, 199 (64% men, 36% women) treated with alkali citrate and 143 (68% men, 32% women) treated with hydrochlorothiazide. Adherence rates were 42% in the alkali citrate group and 52% in the hydrochlorothiazide group (p = 0.05). The main reason for noncompliance in the alkali citrate group (22%) was the number of pills needed to be taken daily. Adverse drug effects were the most common reason for noncompliance in the hydrochlorothiazide group (24%) and in 10% of the alkali citrate group (p < 0.0005). Adherence was poorer in younger patients who did not regularly take other medications than in older patients with other chronic diseases and polypharmacy. Conclusions: About half the patients with clear metabolic abnormalities who were prescribed secondary chemoprevention with hydrochlorothiazide and alkali citrate failed to adhere to the prescribed regimen. Reasons for noncompliance differed between both drugs. The findings of this study may help clinicians to identify patients at risk for nonadherence and suggests potential means to improve compliance rates.
Keywords: adherence; compliance; nephrolithiasis; prevention.