Risedronate prevents exercise-induced hypercalcemia but not nausea or vomit in humans: a double blind randomized controlled trial.

Reportedly, nausea or vomiting after heavy exercise was associated with post-exercise increased blood calcium (Ca) levels, which was correlated with enhanced bone resorption. We conducted a randomized, double-blind, placebo-controlled trial, enrolling 104 healthy trained male members of the Japan Ground Self-Defense Forces. Risedronate (17.5 mg) or placebo was prescribed 3 and 10 days before heavy exercise lasting approximately 5 h. The primary outcome was the severity of nausea or vomiting assessed by a visual analog scale during or post-exercise. The secondary outcomes included clinical symptoms associated with heat illness, post-exercise serum total Ca (tCa), whole blood ionized Ca (iCa), and serum tartrate-resistant acid phosphatase 5b (TRACP-5b) levels. The mean age was 26 years. The exercise resulted in a 4.5% weight loss. The two groups were comparable in terms of the symptoms, including primary outcome. However, post-exercise tCa and TRACP-5b were significantly lower with risedronate. A similar result was observed for iCa. The post-exercise urinary Ca/Magnesium ratio and the incidence of hypercalcemia (defined as tCa or iCa levels ≥ each median value of all subjects) were significantly lower with risedronate (78.0% vs. 58.5%). A stronger treatment effect of risedronate on blood Ca levels was observed in participants who lost substantial body weight. Post-exercise hypercalcemia is attributed to enhanced bone resorption but not the cause of nausea.