RESUMO
OBJECTIVE: Non-dissociation of vitamin B12 from its carrying proteins is the most frequent cause of vitamin B12 deficiency in the elderly. The aim of this study was to determine the initial dose of oral cyanocobalamin that would correct the B12 vitamin deficiency within one week. METHODS: This was an open, prospective, study on 30 elderly patients suffering from vitamin deficiency (B12 < 0.20 microg/L) induced by food-cobalamin malabsorption. Ten patients (group I) were treated with a daily dose of 1000 microg of oral cyanocobalamin (from D1 to D8), 10 (group II) with 1000 microg every other day (D1, D3, D5 and D7), 5 (group III) with 1000 microg every 4 days (D1 and D5) and 5 (group IV) with 1000 microg only on D1. The biological response was assessed by control measurement of vitamin B12 serum levels on the 8th day. RESULTS: Mean vitamin B12 serum levels had significantly increased (p < 0.01) in groups I, II and III, but not in group IV. The dose-effect, assessed by the mean increase in vitamin B12 serum levels, was significantly greater (p < 0.05) in groups I (0.25 microg/L) and II (0.18 microg/L), than in groups III and IV (0.09 microg/L). CONCLUSION: This prospective study shows that an oral dose of 1000 microg of cyanocobalamin every 4 days, which corresponds to 250 microg per day, was sufficient to correct B12 vitamin deficiency induced by food-cobalamin malabsorption within one week. However, initial doses of 1000 microg per day or every other day would be preferable because of the greater dose-effect with daily doses higher than 500 microg. A randomised study is warranted to validate these preliminary results.