However, due to reports of successful oral cobalamin substitution in humans with various gastrointestinal disorders, one of the authors (L. 5, 9, 15 Currently, studies assessing the effect of oral cobalamin supplementation in dogs with CE are lacking. 20, 21, 23, 27, 28 Current supplementation protocols for cobalamin in dogs call for repeated parenteral injections based on pathophysiologic justification, clinical empiric experience, and specialist opinion. 19- 21, 23, 27 Continuous increases of serum cobalamin concentrations during oral cobalamin treatment have been demonstrated in several studies. 19- 21, 26- 29 A daily oral intake of 1,000–2,000 μg cyanocobalamin successfully normalized serum cobalamin in all studies available in human patients. 19, 25, 26 Factors influencing the increase in serum cobalamin concentration after oral administration in humans are dose and time. In European countries, oral cobalamin supplementation is widely utilized. Oral cobalamin is prescribed to human patients to avoid the discomfort, inconvenience, and cost of monthly injections of vitamin B12. 20- 23 A Cochrane review from 2009 reached the same conclusion. 19 Several studies in humans with hypocobalaminemia suggest that the administration of oral cobalamin might be as effective as parenteral administration in restoring serum cobalamin concentrations in patients suffering from pernicious anemia, various gastrointestinal disorders, or for those on a restricted diet (vegetarians and vegans).
DOG PICA DEFICIENCY FREE
18 However, studies in humans using radioactively labeled cobalamin have shown that approximately 1% of free cobalamin was absorbed along the entire intestine by passive diffusion, independently of IF. 3 The cobalamin-IF complex is absorbed by receptors in the ileum. Gastrointestinal processing and absorption of cobalamin in mammals are mediated by carrier proteins and IF, which in dogs is mainly produced by the pancreas. 15 Cobalamin deficiency induces various clinical and metabolic consequences, including anorexia, weight loss, failure to thrive, central and peripheral neuropathies, immunodeficiency, and intestinal changes including villous atrophy and malabsorption of other vitamins and nutrients. 9, 14 Suggested mechanisms of cobalamin deficiency in canine CE are damage to the ileal mucosal receptors for binding of cobalamin–intrinsic factor (IF) complexes or bacterial competition for nutrients in small intestinal dysbiosis resulting in decreased amounts of cobalamin available for absorption. 9- 13 Hypocobalaminemia has also been reported to be a negative prognostic factor in dogs with CE or EPI, associated with an increased risk of euthanasia. 7, 8 Cobalamin deficiency in dogs is commonly associated with canine CE with a reported prevalence of 6–73%. 1- 6 Anecdotal reports of short-bowel syndrome and cobalamin deficiency in dogs also exist, an association that is well documented in humans.