Renal stone risk during spaceflight: assessment and countermeasure validation

Potassium citrate, a proven Earth-based therapy to minimize calcium-containing renal stone development, is being tested in a double-blind study as a countermeasure to reduce the risk of renal stone formation in crewmembers on the International Space Station. Subjects ingest two potassium citrate or placebo pills with the last meal of the day from L-3 (days prior launch) to R+14 (days after landing). Food, fluid, exercise, and medications are monitored for 48 hours (24 hours prior to and during the 24-hour urine collection period) to assess environmental influences other than microgravity.