Vitamin-B12-mangel als komplikation chronischer
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Cobalamin (vitamin B12) serves as an important co-factor for enzymes involved in the metabolism of amino- and fatty acids and the synthesis of purine and pyrimidine bases. Accordingly, disturbances of the citric cycle and energy metabolism as well as protein synthesis and cell division are consequences of cobalamin deficiency. Since the absorption of cobalamin is complex and the receptors required for the absorption are exclusively located in the ileum, disease of the ileal mucosa can lead to destruction of receptors, leading to malabsorption of the vitamin. In case of a deficiency, the serum concentration of cobalamin is usually low. However, it takes long-standing disease, usually several weeks, for cobalamin deficiency to develop. The clinical diagnosis of cobalamin deficiency is often difficult, because clinical signs are non-specific. Some authors are convinced that therapy of the underlying disease could remain unsuccessful unless cobalamin is also supplemented. Therefore, all patients with cobalamin deficiency should receive cobalamin supplementation. Patients whose values are within the lower end of the reference range should also be supplemented. In cats approximately 250 g and in dogs 250-1500 g are repeatedly administered subcutaneously over a period of several weeks. These dosages are much higher than the physiologic food-intake of cobalamin, but to date there is no evidence that over-supplementation is associated with any side effects. There is even speculation that some of the benefits seen in human patients that are being supplemented with cobalamin might be due to a pharmacologic effect of cobalamin.
