A comparison of sublingual and intranasal routes for administration of vitamin B12 to human subjects

Clinical studies have compared the efficacy of intravenous versus intramuscular, orally ingested versus intramuscular, sublingual transmucosal versus intramuscular as well as intranasal transmucosal versus intramuscular vitamin B12 supplementation; however, sublingual transmucosal versus intranasal transmucosal vitamin B12 supplementation has never been compared. This study recruited 55 subjects without preexistent vitamin B12 deficiency and compared the serum vitamin B12 level 2 hours following sublingual transmucosal and intranasal transmucal administration of a 500 mcg cyanocobalamin USP gel. One subject failed to complete the study.;Although no statistically significant difference between the serum vitamin B12 levels was expected after sublingual versus intranasal administration of 500 mcg of cyanocobalamin USP gel, it was found that intranasal administration resulted in a significant although temporary elevation in serum vitamin B12 levels as compared to oral administration (p-value <0.0001). Serum vitamin B12 levels following intranasal administration increased by a mean of 528 mcg/dL, while serum vitamin B12 levels following oral administration increased by a mean of 57 mcg/dL. Despite the 9 fold greater dose response for intranasal administration, the one month persistence of a single 500 mcg dose of vitamin B12 was nonexistent for both routes of administration, with the change in the mean pre-dose serum vitamin B12 level of 0.52 mcg/dL for oral dosing and -4.78 mcg/dL for intranasal dosing.;Based on the results of this small study, intranasal administration of cyanocobalamin is more efficacious than the sublingual route of administration. Although a larger study with more frequent serum vitamin B12 sampling to determine a dose response curve for each administration route is needed to provide a definitive answer to the question of most efficacious route of administration for vitamin B12, this study powerfully suggests that intranasal administration of vitamin B12 500 mcg/uL gel is superior to sublingual administration. A secondary analysis of the data did real, however, a concerning trend suggesting that, even in healthy subjects without vitamin B12 deficiency, there is no persistent effect on serum vitamin B12 levels after a single 500 mcg dose of vitamin B12 by either the intranasal route or the oral route.