Retention of Crystalline Vitamin B12 by Healthy Male Individuals Following Intramuscular Injection

Abstract

Crystalline vitamin B₁₂ was administered intramuscularly to groups of healthy male subjects at the following levels: 20, 30, 50, and 75 µg. Urinary collections from each subject were made during 24 hours after injection, each in two fractions representing the first 8 hours and the following 16 hours. The vitamin B₁₂ microbiological activities in the urine specimens were measured. These data permitted calculation of the amount retained, by taking the difference between the injected and the excreted vitamin. It was found that more than 50 µg of vitamin were retained daily by these subjects, depending on the dosage administered.