Patiromer is a non-absorbed, cation exchange polymer that contains a calcium-sorbitol complex as a counterion.
Patiromer increases faecal potassium excretion through binding of potassium in the lumen of the gastrointestinal tract. Binding of potassium reduces the concentration of free potassium in the gastrointestinal lumen, resulting in a reduction of serum potassium levels.
In healthy adult subjects, patiromer caused a dose dependent increase in faecal potassium excretion, and a corresponding decrease in urinary potassium excretion with no change in serum potassium. 25.2 g of patiromer, administered once daily for 6 days, resulted in a mean increase in faecal potassium excretion of 1,283 mg/day, and a mean decrease in urinary potassium excretion of 1,438 mg/day. Daily urinary calcium excretion increased from baseline by 53 mg/day.
In an open label study to assess the time to onset of action, a statistically significant reduction in serum potassium in hyperkalaemic patients was observed at 7 hours after the first dose. Following discontinuation of patiromer, potassium levels remained stable for 24 hours after the last dose, then rose again during a 4-day observation period.
Patiromer works by binding potassium in the gastrointestinal tract and thus the serum concentration is not relevant for its efficacy. Due to the insolubility and nonabsorptive characteristics of this medicinal product, many classical pharmacokinetic studies cannot be carried out.
Patiromer is excreted approximately 24 to 48 hours after intake, based on average gastrointestinal transit time.
In radiolabeled studies in rats and dogs, patiromer was not systemically absorbed and was excreted in the faeces. Quantitative whole-body autoradiography analysis in rats demonstrated that radioactivity was limited to the gastrointestinal tract, with no detectable level of radioactivity in any other tissues or organs.
Non-clinical data reveal no special hazard for humans based on conventional studies of safety pharmacology, repeated dose toxicity, genotoxicity, toxicity to reproduction and development.
Patiromer was not genotoxic in the reverse mutation test (Ames assay), chromosome aberration or rat micronucleus assays.
Carcinogenicity studies have not been performed.
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