Early biochemical and hematological response to intramuscular cyanocobalamin therapy in vitamin B(12)-deficient patients.

Background: Data on early biochemical and hematological responses to cobalamin therapy in vitamin B12-deficient patients are scarce. Therefore, we investigated whether cobalamin injections would include prompt biochemical and hematological responses in vitamin B12-deficient patients.

Subjects And Methods: Seven female patients (mean age: 69.4 years, range: 61-78) with a mean serum cobalamin level of 104 ± 38 pmol/l mean ± SD and 7 male patients (mean age: 67.0 years, range: 53-78) with a mean serum cobalamin level of 84 ± 40 (±SD) participated in the study. They were administered 1 mg i.m. cyanocobalamin per week for 3 weeks. Blood samples were collected before and 1, 3, 7, 14 and 21 days after cobalamin injection. The concentrations of plasma aminothiols and serum methylmalonic acid (MMA) were measured with high-performance liquid chromatography and gas chromatography/mass spectrometry, respectively, and hematological parameters were determined with a hematological analyzer.

Results: Already 1 day after intramuscular Cobalamin injections, the concentrations of serum vitamin B12 and plasma total cysteine were significantly increased while the concentrations of serum folate, plasma total homocysteine and serum MMA were decreased. Mean cell volume was also significantly decreased first after 14 days of therapy.

Conclusion: Intramuscular cobalamin administration causes swift and significant changes in plasma aminothiols, whereas the first change in hematological parameters was detected only after 14 days.