Conditions: Hyperkalemia Chronic Kidney Disease Kidney Dysfunction
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 90
Healthy volunteers: no

Brief summary:
It is hypothesized that zirconium silicate is safe and well tolerated and more effective than placebo (alternative hypothesis) in lowering serum potassium levels in subjects with serum potassium between 5 - 6.0 mmol/l versus no difference between zirconium silicate and placebo (null hypothesis). It is hypothesized that zirconium silicate even up to the top dose of 10g three times a day is well tolerated.

Detailed description:
A total of 90 subjects with moderate CKD (defined as GFR between 40- 60ml/min) and mild hyperkalemia (S-K between 5-6 mmol/l) will be enrolled in the study where, in a double-blind dose-escalating fashion (three separate cohorts), they will be randomized to receive one of the doses of ZS (0.3g, 3g and 10g) or placebo, administered 3 times (tid) daily with meals. The first cohort will have 18 subjects while both of the second and third cohorts will have 36 subjects for a total of 90 subjects.

Safety and tolerability will be assessed by an Independent Data Safety Monitoring Board (DSMB) after completion of each cohort, before escalation to the next dose level will be allowed. The next dose escalation will happen no sooner than one week after the last dose of study drug at the previous dosing level has been administered. Safety stopping rules will be specified for this study. Within the first dose level (300 mg dose), 12 subjects will be randomized to receive ZS, whereas 6 subjects will be randomized to receive placebo for a total of 18 subjects in this first cohort. In the next two cohorts (3 g and 10 g doses), 24 subjects per cohort will be randomized to receive ZS, whereas 12 subjects per cohort will be randomized to receive placebo for a total of 36 subjects in each of the second and third cohorts.

Arms:
arm 1: Placebo (silicified microcrystalline cellulose) randomized to mimic escalating doses of experimental drug administered three times daily (TID) with meals. arm 2: Randomized escalating doses (0.3g, 3g and 10g) of ZS (fractionated, protonated, microporous zirconium silicate, an oral sorbent) administered 3 times daily (tid) with meals.

Interventions: intervention 1: Zirconium silicate (ZS) intervention 2: Placebo
Intervention descriptions: intervention 1: Randomized escalating doses (0.3g, 3g and 10g) of ZS (fractionated, protonated microporous Zirconium Silicate, an oral sorbent) administered 3 times daily (tid) with meals. intervention 2: Randomized to mimic escalating doses of experimental drug administered 3 times daily (tid) with meals.

Protocol document: