Stability of cyanocobalamin in parenteral preparations.

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Karachi, Karachi-75270, Pakistan.
Pakistan journal of pharmaceutical sciences (Impact Factor: 0.95). 02/1993; 6(1):53-9.
Source: PubMed

ABSTRACT 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.

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    ABSTRACT: A comparison of the degradation of cyanocobalamin (vitamin B(12)) solutions on exposure to sunlight and artificial light has been made using two concentrations, i.e. 950 mug/ml (corresponding to parenteral solutions) and 95 mu/ml (1:10 dilution) at pH 4.0, 5.5 and 7.0. Cyanocobalamin and the photoproduct, hydroxocobalamin (vitamin B(12b)), have been determined by a two component spectrophotometric method at 550 and 525 nm. Cyanocobalamin loss (950 mug/ml and 95 mug/ml) on exposure to sunlight for 2 hours amounts to 14.7-21.0% and 56.3-81.5% respectively indicating that light intensity is the rate determining factor in the reaction. In artificial light for 2 hours B(12) (950 mug/ml and 95 mug/ml) loses and 1.5-27.7% respectively. Thus B(12) degradation in sunlight is greater compared to that of the artificial light, with the formation of some oxidation products, in addition to B(12b).
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    ABSTRACT: The degradation kinetics of 5 × 10(-5) M cyanocobalamin (B12) and hydroxocobalamin (B12b) in the presence of ascorbic acid (AH2) was studied in the pH range of 1.0-8.0. B12 is degraded to B12b which undergoes oxidation to corrin ring cleavage products. B12b alone is directly oxidized to the ring cleavage products. B12 and B12b in degraded solutions were simultaneously assayed by a two-component spectrometric method at 525 and 550 nm without interference from AH2. Both degrade by first-order kinetics and the values of the rate constants at pH 1.0-8.0 range from 0.08 to 1.05 × 10(-5) s(-1) and 0.22-7.62 × 10(-5) s(-1), respectively, in the presence of 0.25 × 10(-3) M AH2. The t 1/2 values of B12 and B12b range from 13.7 to 137.5 h and 2.5-87.5 h, respectively. The second-order rate constants for the interaction of AH2 with B12 and B12b are 0.05-0.28 × 10(-2) and 1.10-30.08 × 10(-2) M(-1) s(-1), respectively, indicating a greater effect of AH2 on B12b compared to that of B12. The k obs-pH profiles for both B12 and B12b show the highest rates of degradation around pH 5. The degradation of B12 and B12b by AH2 is affected by the catalytic effect of phosphate ions on the oxidation of AH2 in the pH range 6.0-8.0.
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    ABSTRACT: Export Date: 18 October 2014
    Advanced Pharmaceutical Bulletin 12/2014; 4(4):329-338. DOI:10.5681/apb.2014.048 · 0.88 Impact Factor


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