Erythropoietic effects of low‐dose cobalt application

Cobaltous ions (Co 2+ ) stabilize HIFα, increase endogenous erythropoietin (EPO) production, and may, therefore, be used as a performance‐enhancing substance. To date, the dosage necessary to stimulate erythropoiesis is unknown. The aim of this study was, therefore, to determine the minimum dosage necessary to increase erythropoietic processes. In a first double‐blind placebo‐controlled study ( n  = 5), single oral Co 2+ dosages of 5 mg ( n  = 6) and 10 mg ( n  = 7) were administered to healthy young men. Cubital venous blood and urine samples were collected before and up to 24 hours after Co 2+ administration. In a second study, the same daily Co 2+ dosages were administered for five days (placebo: n  = 5, 5 mg: n  = 9, 10 mg: n  = 7). Blood and urine samples were taken the day before administration and at day 3 and day 5. Plasma [EPO] was elevated by 20.5 ± 16.9% at 5 hours after the single 5‐mg administration ( p  < 0.05) and by 52.8 ± 23.5% up to 7 hours following the 10‐mg Co 2+ administration ( p  < 0.001). Urine [Co 2+ ] transiently increased, with maximum values 3–5 hours after Co 2+ ingestion (5 mg: from 0.8 ± 1.1 to 153.6 ± 109.4 ng/mL, 10 mg: from 1.3 ± 1.7 to 338.0 ± 231,5 ng/mL). During the five days of Co 2+ application, 5 mg showed a strong tendency to increase [EPO], while the 10‐mg application significantly increased [EPO] at day 5 by 27.2 ± 26.4% ( p  < 0.05) and the immature reticulocyte fraction by 49.9 ± 21.7% ( p  < 0.01). [Ferritin] was decreased by 12.4 ± 10.4 ng/mL ( p  < 0.05). An oral Co 2+ dosage of 10 mg/day exerts clear erythropoietic effects, and 5 mg/day tended to increase plasma EPO concentration.