Rajan Suparna, Wallace Jeffrey I, Brodkin Kayla I, Beresford Shirley A, Allen Robert H, Stabler Sally P
Seattle Veteran Affairs Puget Sound Health Care System, Seattle, Washington, USA.
J Am Geriatr Soc. 2002 Nov;50(11):1789-95. doi: 10.1046/j.1532-5415.2002.50506.x.
Because the effects of lower-dose oral cobalamin (Cbl) supplements on older people with cobalamin deficiency are not known, we determined whether oral Cbl supplements at three different dose levels would normalize elevated serum methylmalonic acid (MMA) and total homocysteine (tHcy) concentrations.
Sequential nonrandomized intervention study of three dose levels.
Two university-based senior care clinics.
Twenty-three older adults (aged >/=65) with serum Cbl levels of 221 pmol/L (300 pg/mL) or lower and serum MMA greater than 271 nmol/L who had been enrolled in a previous screening study for Cbl deficiency (mean age 79 +/- 9; 17 male, 6 female; 17 white, 6 other).
Sequential daily treatment with 25 microg oral cobalamin, followed by 100 microg and 1,000 microg cobalamin each for a 6-week period.
Serum MMA, tHcy, and other metabolites at baseline and after each 6-week dosing interval.
Treatment with 25 microg and 100 microg lowered but did not normalize MMA levels in most subjects. A dose of 1,000 microg/day proved to be the most effective in lowering MMA levels to within normal limits. Serum tHcy was normalized in six of 11 subjects who had elevated tHcy pretreatment with oral Cbl alone and in one subject in combination with a multivitamin.
Most Cbl-deficient older people require more than 100 microg of oral Cbl to normalize serum MMA, which is a larger dose than is available in most standard multivitamins and Cbl supplements.
由于低剂量口服钴胺素（Cbl）补充剂对钴胺素缺乏的老年人的影响尚不清楚，我们确定了三种不同剂量水平的口服Cbl补充剂是否能使升高的血清甲基丙二酸（MMA）和总同型半胱氨酸（tHcy）浓度恢复正常。
三种剂量水平的序贯非随机干预研究。
两家大学附属的老年护理诊所。
23名年龄≥65岁的老年人，血清Cbl水平为221 pmol/L（300 pg/mL）或更低，血清MMA大于271 nmol/L，这些人曾参加过先前的钴胺素缺乏筛查研究（平均年龄79±9岁；17名男性，6名女性；17名白人，6名其他种族）。
依次每日服用25微克口服钴胺素，随后各服用6周的100微克和1000微克钴胺素。
在基线以及每个6周给药间隔后测量血清MMA、tHcy和其他代谢物。
大多数受试者服用25微克和100微克剂量时，MMA水平有所降低但未恢复正常。事实证明，每日1000微克的剂量在将MMA水平降至正常范围内最为有效。在11名治疗前tHcy升高的受试者中，有6名仅通过口服Cbl使血清tHcy恢复正常，还有1名受试者联合服用多种维生素后恢复正常。
大多数钴胺素缺乏的老年人需要超过100微克的口服Cbl才能使血清MMA恢复正常，这一剂量比大多数标准多种维生素和Cbl补充剂中的剂量要大。
