Research into transmucosal absorption of intranasal Vitamin B12 gel supports a significant absorptive capacity for Vitamin B12 by this route. Given that the mucosal thickness of the intranasal mucosa compared to the sublingual mucosa is approximately the same in that mucosal vascularity is also approximately the same such dispirit results between the two routes would not be expected based on a pharmacokinetic difference alone. Given that both areas are supplied by branches of the carotid artery and therefore have the same flow rates, vascular profusion also fails to explain the disparity of results that is in fact seen when these routes are compared. The most logical and obvious explanation is that the intranasal administration allowed for a retention time greater that found sublingual administration of Vitamin B12 gel. This "holding time" allowed for a greater absorption of the Vitamin B12 gel.
Although this has interesting implications for the treatment of Vitamin B12 deficiency in a number of patient types including those with Dumping Syndrome and Pernicious Anemia, all other patient populations with Vitamin B12 deficiency have been shown to be adequately supplemented by high dose oral Vitamin B12. The intranasal use of Vitamin B12 gel does represent an opportunity to treat those patients for whom oral Vitamin B