The median increase in the potassium level from baseline of that phase was greater with placebo than with patiromer ( P < 0.001 ) ; a recurrence of hyperkalemia ( potassium level , 5.5 mmol per liter ) occurred in 60 % of the patients in the placebo group as compared with 15 % in the patiromer group through week 8 ( P < 0.001 ) .