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 than found in sublingual administration of Vitamin B12 gel. This “holding time” allowed for 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 B12 is either unacceptable as an administration route or ineffective due to decreased intestinal transit time or the lack of intrinsic factor.
Of far greater potential if the application of this research to the treatment to cyanide poisoning. The incidence of cyanide poisoning as an industrial exposure continues to this day to be a significant occupational risk worldwide. Although that risk is significantly lower in industrial countries due to the shift to a more technological economy third world countries continue to use large volumes of cyanide and its conjurers in the manufacture of precious metals and the processing of gemstones and other products. The most famous of these accidents occurred in Bhopal, India in 1984 when 40 million tons of methyl-isocyanate was inadvertently released by a union carbide plant worker. The number of casualties quickly outstripped the medical capabilities of the local community and the casualty rate both for disabled and dead was astronomical.
The loss of the amyl nitrate-based cyanide treatment kit has created a void in the continuum of care for cyanide-exposed patients. The amyl nitrate-based cyanide treatment kit allowed for a bystander with no medical training to read simple picture-based instructions and administered the first, life-sustaining step in cyanide treatment. In many cases, individuals exposed to cyanide can self treat in using this first amyl nitrate-based step since it required only that the amyl nitrate ampoules be open and poured on gauze or another cloth which could then be held to the face and the medicine breathed in.
The new Vitamin B12-based cyanide treatment kit, while safer, requires the reconstitution of powdered Vitamin B12 and administration by use of an intravenous infusion. While this is a relatively simple procedure for an experienced health care professional it is beyond the reach of most bystanders and prohibitively difficult if not impossible to be performed by cyanide-exposed individuals upon themselves.
Transmucosal administration suggests a potential solution that will fill the void between immediate field care between cyanide toxic related toxicity and dissentative intravenous care using a Vitamin B12 base cyanide treatment kit. The volume of Vitamin B12 gel required would exceed that reasonable for intranasal use, but an intrarectal route would provide both adequate volume capacity and holding time.
Currently, there are several intra-rectal treatments utilized in toxicology and emergency medicine. Intra-rectal diazepam is utilized for the treatment of seizures by school nurses, parents, and in a limited number of situations by patients during their pre-seizure aura. Kayexalate is utilized extensively for hyperkalemia whether a result of renal failure or muscular injury from glass or crushed trauma intra-rectal kayexalate.
In both of these treatments volumes of medication between ten and 120 milliliters are instilled and retained in the rectum allowing for the absorption of medication across the rectal mucosa. Like the intranasal mucosa the rectum mucosa is relatively thin and of approximately the same vascularity and profusion rate.
The scientific literature suggests that a Vitamin B12 gel at a concentration similar to that described in multiple British research projects (15 to 20 milligrams per milliliter) would result in a dose comparable to half of the total Vitamin B12-based cyanide treatment kit. This dose of 1.8 to 2.4 grams could be repeated in four hours allowing for the administration of the entire recommended 5 gram Vitamin B12 dose for moderate to severe cyanide toxicity within the recommended six hours via the rectal retention method alone.
Although further, more specific research on the utilization of high-dose Vitamin B12 intra-rectal gel in the treatment of cyanide toxicity would be required before a definitive recommendation could be made for this route of administration; the potential of this route is clearly supported by the literature. Transmucosal Vitamin B12 may represent the missing link in the care of cyanide-related toxicity both in industrial and tourism-related exposures.
