Stability of cyanocobalamin in parenteral preparations.

The stability of seven commercial parenteral preparations of cyanocobalamin (vitamin B(12)) on storage under normal laboratory conditions for a period of twelve months has been studied using a two component spectrophotometric method for the simultaneous determination of cyanocobalamin and the degradation product, hydroxocobalamin, at 550 and 525 nm. The single ingredient vitamin B(12) preparations have been found to be stable and the potency lies within the B.P. limits. In multi-ingredient (B(1) + B(6) + B(12)) preparations cyanocobalamin is unstable and degrades from 28% to 37% with concomitant formation of hydroxocobalamin (1.7% to 25.5%) and oxidation products amounting to 56.4% +/- 9.3. Thus more than half of the vitamin content is lost during storage and these preparations are not suitable for parenteral use.