A troche is a soft, slow-dissolving lozenge held under the tongue. The sublingual mucosa is thin, non-keratinised and richly vascularised, draining into the jugular vein, so anything absorbed there enters circulation without passing through the gut lumen or the liver first. That avoids both proteolytic digestion and first-pass hepatic metabolism, the two mechanisms that reduce oral peptide bioavailability to fractions of a percent.
Why troches matter in peptide research
The advantage is real but bounded. Sublingual surface area is small, contact time is limited by swallowing, and the mucosa still favours small, moderately lipophilic molecules. Peptides are large and hydrophilic, so measured sublingual absorption is usually modest and formulation-sensitive; permeation enhancers and pH adjusters in the base matter as much as the peptide itself. Anything not absorbed is swallowed and behaves like an oral amount.
Troche bases are typically polyethylene glycol or gelatin with a sweetener and a flavouring, all of which count as excipients and none of which appear on a peptide certificate of analysis unless the vendor states the full formulation. Catalogue examples include AOD-9604 troches and oxytocin troches; format trade-offs are covered in the oral peptides guide.