Oral semaglutide, despite its commercial availability, achieves only 0.4–1% absolute bioavailability under strict fasting conditions — and essentially zero systemic exposure when taken with food, as plasma concentrations fall below quantification limits. Its absorption mechanism depends entirely on the co-excipient SNAC (sodium N-[8-(2-hydroxybenzoyl)amino] caprylate), which raises local gastric pH, suppresses pepsin, preserves semaglutide in absorbable monomeric form, and facilitates transcellular uptake. Even so, individual absorption fluctuates dramatically, though semaglutide's ~7-day half-life and tight albumin binding effectively smooth out day-to-day variability at steady state.
This review crystallizes a tension that defines the entire oral peptide therapeutics field: the gastrointestinal tract is a ferociously hostile environment for large molecules, and SNAC is a clever but partial solution. For practicing clinicians and patients, the practical implication is that the oral form demands rigid adherence — fasting, minimal water, precise timing — a regimen that erodes real-world adherence advantages over once-weekly subcutaneous injection. The authors' survey of next-generation approaches — lipid nanoparticles, permeation enhancers beyond SNAC, protease inhibitors, and ingestible microneedle devices — reflects genuine industry momentum, but most remain preclinical. This is a review paper, not primary data, so it offers no new clinical endpoints. Its value lies in consolidating the mechanistic landscape. For longevity-focused audiences, semaglutide's metabolic and potential aging-pathway benefits are only accessible if delivery is solved — making bioavailability engineering arguably as consequential as the molecule itself.