The Role and Effectiveness of Oral Vitamin B12 Therapy in Pernicious Anemia
Özet
Vitamin B12 deficiency is a clinically significant and frequently underdiagnosed condition that can lead to a wide spectrum of hematological, neurological, and systemic complications if not promptly identified and treated. At the hematological level, deficiency results in megaloblastic anemia, characterized by macrocytosis, ineffective erythropoiesis, and pancytopenia in severe cases. From a neurological standpoint, vitamin B12 deficiency may cause peripheral neuropathy, ataxia, impaired proprioception, cognitive dysfunction, and, in advanced cases, irreversible neuropsychiatric deterioration. Beyond these, systemic manifestations, including glossitis, infertility, osteoporosis, and increased cardiovascular risk, have also been reported, emphasizing the multisystemic impact of this essential micronutrient. Among the various causes of deficiency, pernicious anemia remains one of the most common, arising from intrinsic factor deficiency due to autoimmune destruction of gastric parietal cells and subsequent failure of cobalamin absorption in the terminal ileum.
For many decades, the parenteral administration of vitamin B12 has been regarded as the only reliable therapeutic approach, largely because of the belief that gastrointestinal absorption is insufficient in patients with pernicious anemia or other malabsorptive conditions. Intramuscular or subcutaneous injections of hydroxocobalamin or cyanocobalamin have become standard practice, and although highly effective in replenishing cobalamin stores, the requirement for repeated injections often limits adherence, creates logistical challenges for both patients and healthcare providers, and increases the burden on the healthcare system. In recent years, however, a growing body of clinical evidence has demonstrated that high-dose oral vitamin B12 therapy, by relying on passive diffusion mechanisms independent of intrinsic factors, can achieve comparable hematological and neurological outcomes in many patients. Randomized controlled trials, systematic reviews, and observational cohort studies have increasingly confirmed the efficacy, safety, and practicality of oral therapy, leading to its acceptance as a viable alternative in numerous international guidelines.
This book provides a comprehensive and up-to-date review of the pathophysiology, clinical manifestations, diagnostic approaches, and therapeutic strategies related to vitamin B12 deficiency, with a particular focus on pernicious anemia as the prototypical cause of impaired cobalamin absorption. Drawing upon a wide range of literature data, recent clinical research, and original study findings, this study specifically evaluates the role and effectiveness of oral vitamin B12 therapy in comparison to parenteral approaches. Special emphasis was placed on its advantages in terms of patient compliance, cost-effectiveness, ease of administration, and overall impact on long-term outcomes. In addition, the discussion addresses the evolving perspectives in clinical practice, including the integration of oral therapy into treatment algorithms, its potential role in special patient populations, such as the elderly, bariatric surgery patients, and pregnant women, and the ongoing debates about optimal dosing and monitoring strategies.
In conclusion, this work is intended to serve not only as a practical guide, but also as a scientific resource for gastroenterologists, hematologists, internists, and all physicians who encounter vitamin B12 deficiency in daily clinical practice. By synthesizing current knowledge with clinical applicability, it aims to contribute to a more effective, individualized, and patient-friendly management of pernicious anemia, ultimately improving both the quality of care and patient outcomes.
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