Absorption of Vitamin B12 in Older Adults: Advances and Challenges in Sublingual Administration

The aim of this review is to analyze current routes for the administration and absorption of vitamin B12 in older adults, with a special focus on the sublingual route using orodispersible films, and evaluate the advances, materials, and challenges associated with this method of administration. Thus, the review aims to provide an updated overview of safe and effective alternatives for preventing and treating vitamin B12 deficiency in this age group. Vitamin B12 deficiency predominantly affects older adults. After the age of 70, absorption decreases, and deficiency occurs most frequently due to age-related gastric atrophy, decreased gastric acid production, reduced intrinsic factor secretion, and inadequate dietary vitamin B12 intake. This narrative review examines traditional and current treatments for vitamin B12 administration in older adults, with a focus on sublingual administration (SL) via orodispersible films (ODFs) to enhance absorption, adherence, and accessibility. SL vitamin B12 bioavailability, advantages versus disadvantages, ODF formulations (polymers such as pregelatinized starch, HPMC, and chitosan), and pharmaceutical process challenges (solvent casting and hot-melt extrusion) were explored in the reviewed in vitro and in vivo studies. According to the collected evidence, the sublingual route appears to offer rapid absorption directly into the bloodstream, with efficacy comparable to/superior to intramuscular (IM)/oral (OP) routes of administration, representing a patient-centered innovation for older adults that overcomes painful treatments and gastrointestinal/swallowing barriers. Future longitudinal clinical trials should validate long-term efficacy, standardize materials, and scale up to viable industrial production, addressing issues related to chemical stability and polypharmacy.