Case 30-2004: A Woman with Paresthesias
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《新英格兰医药杂志》
To the Editor: In reference to the discussion of pernicious anemia in Case 30-2004 (Sept. 23 issue),1 the practice in the United Kingdom for many years has been a regimen of four intramuscular injections of 1000 μg of hydroxocobalamin (an injectable form of vitamin B12) per year in patients with pernicious anemia, usually given every three months. This treatment follows initial therapy comprising four or five 1000-μg doses given over a period of approximately four weeks. That this constitutes adequate replacement therapy is evident from widely shared experience. Pharmacokinetic evidence provides a sound basis for this practice; 500 μg of hydroxocobalamin given parenterally raises the cobalamin level to more than 100 μg per liter for a mean of 289 days.2 Why, then, are monthly doses of vitamin B12 recommended?
Simon V. Davies, F.R.C.P., F.R.C.Path.
Taunton and Somerset Hospital
Taunton TA1 5DA, United Kingdom
simon.davies@tst.nhs.uk
References
Case Records of the Massachusetts General Hospital (Case 30-2004). N Engl J Med 2004;351:1333-1341.
Tudhope GR, Swan HT, Spray GH. Patient variation in pernicious anaemia as shown in a clinical trial of cyanocobalamin, hydroxocobalamin and cyanocobalamin-zinc tannate. Br J Haematol 1967;13:216-228.
Dr. Marks replies: Dr. Davies's comment regarding the schedule of vitamin B12 injections is very well taken. Evidence-based medicine would certainly suggest that vitamin B12 at a dose of 1 mg by intramuscular injection every three months is adequate maintenance therapy for patients with pernicious anemia. Fewer visits are certainly beneficial from the perspective of convenience and cost, provided that compliance is appropriate.
As noted in the discussion in the case record, a variety of vitamin B12 replacement regimens may be used, including an oral regimen. Apropos of Dr. Davies's question, the other puzzling question is why oral vitamin B12 replacement therapy is not used more widely, given its demonstrated efficacy, convenience, and low cost.1
Perhaps the most honest answer to both questions is that habit, rather than evidence, often drives clinical practice.
Peter W. Marks, M.D., Ph.D.
Novartis Oncology
East Hanover, NJ 07936
peter.marks@pharma.novartis.com
Simon V. Davies, F.R.C.P., F.R.C.Path.
Taunton and Somerset Hospital
Taunton TA1 5DA, United Kingdom
simon.davies@tst.nhs.uk
References
Case Records of the Massachusetts General Hospital (Case 30-2004). N Engl J Med 2004;351:1333-1341.
Tudhope GR, Swan HT, Spray GH. Patient variation in pernicious anaemia as shown in a clinical trial of cyanocobalamin, hydroxocobalamin and cyanocobalamin-zinc tannate. Br J Haematol 1967;13:216-228.
Dr. Marks replies: Dr. Davies's comment regarding the schedule of vitamin B12 injections is very well taken. Evidence-based medicine would certainly suggest that vitamin B12 at a dose of 1 mg by intramuscular injection every three months is adequate maintenance therapy for patients with pernicious anemia. Fewer visits are certainly beneficial from the perspective of convenience and cost, provided that compliance is appropriate.
As noted in the discussion in the case record, a variety of vitamin B12 replacement regimens may be used, including an oral regimen. Apropos of Dr. Davies's question, the other puzzling question is why oral vitamin B12 replacement therapy is not used more widely, given its demonstrated efficacy, convenience, and low cost.1
Perhaps the most honest answer to both questions is that habit, rather than evidence, often drives clinical practice.
Peter W. Marks, M.D., Ph.D.
Novartis Oncology
East Hanover, NJ 07936
peter.marks@pharma.novartis.com