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2–5 µg of B12 IM for 8–15 d.

Five persons who were given 3 µg/d of B12 for 15 d had a reticulocyte response that was not followed by a further response to more B12. This amount allowed restoration of status.

1 mg of slow-release B12 IM every 2 or 3 mo for at least 8 y. The less-frequent dose was equivalent to 1.7 µg of B12/d.b

Serum B12 values were well above the cutoff of 180 pmol/L (250 pg/mL) early in the study and complete hematological remission occurred in all.

35 received 1 mg of B12 IM every 5–6 mo, 6 received it every 3–4 mo, 3 received it every 2 mo. Smallest and most frequent dose was equivalent to 0.8–1.0 µg of B12/d.d

From total group analyses, 14 subjects had mild hematological relapse on 42 occasions; 34 subjects had at least one abnormal serum B12 or metabolite value on 146 occasions when there was no evidence of hematological relapse.

2.0 µg oral dose of B12 Co60 given with intrinsic factor.

With 70% absorption, complete hematological response, and adequate plasma B12 concentration, 1.4 µg of absorbed B12 met the requirements of two-thirds of the subjects.

10 µg of B12 given IM every 2 wk or 20 µg of B12 given IM monthly for 10 y (equivalent average of 0.7 µg/d).

None of the subjects maintained serum B12 concentration above the 180 pmol/L (250 pg/mL) lower limit of normal for the Lactobacillus leichmannii method.

0.1 µg/d of cyanocobalamin IM for 10 d; 0.1 µg/d of coenzyme B12 IM for 10 d.

Posttreatment serum B12 was 85 pmol/L (60 pg/mL) (range, 20–200 pmol/L [14–139 pg/mL]); 6 of 8 had reticulocyte response, but macrocytosis persisted in all and hypersegmentation did in many. In some, neurological abnormalities progressed until at least 1 µg of B12 was given daily. All but one were later given higher doses of B12.

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