Acute renal failure in four Comrades Marathon runners ingesting the same electrolyte supplement: coincidence or causation?

OBJECTIVES To evaluate common factors associated in the development of acute renal failure (ARF) in Comrades Marathon runners. METHODS This was a retrospective case series of 4 runners hospitalised post-race with ARF in the 89 km 2010 Comrades Marathon. The outcome measures were incidence of analgesic use, levels of creatine phosphokinase (CPK) and degree of electrolyte supplementation (sodium, potassium, calcium and magnesium). RESULTS The incidence of ARF was 1/4 125 runners. They presented with rhabdomyolysis (mean admission CPK of 36 294 IU) and hyponatraemia (mean admission blood sodium level of 133 mEq/l). All had ingested an analgesic during the run (3 ingested a non-steroidal anti-inflammatory drug) and the same readily available anti-cramp electrolyte supplement. The average amount of supplemental sodium (452 mg), potassium (393 mg), calcium (330 mg) and magnesium (154 mg) ingested via this particular electrolyte supplement before and during the run did not exceed the recommended upper limits of daily intake. Three of the runners were Comrades Marathon novices. CONCLUSIONS There is a continuing need to clarify the specific cluster variants that cause ARF in Comrades Marathon runners, as the risk factors appear to have evolved since the first case described over 40 years ago.