Bioavailability
Fraction of dose reaching systemic circulation
Bioavailability (F) is the fraction of an administered dose that reaches systemic circulation in unchanged form. Intravenous administration is defined as 100% bioavailable; every other route is compared to it.
Most research peptides have very poor oral bioavailability — often well under 1% — because peptide bonds are degraded by gastric proteases and the molecule is too large for efficient enterocyte uptake. This is the reason subcutaneous and intramuscular injection dominate peptide research protocols. Notable exceptions include MK-677 (a small molecule with ~60% oral F), orforglipron (an oral GLP-1 small molecule), and stable variants of BPC-157 with researched oral activity.
Intranasal delivery (Semax, Selank) bypasses the gut entirely and provides reasonable CNS bioavailability for small peptides. Topical formulations (GHK-Cu, Argireline) act locally and have negligible systemic exposure.
Used in 3 research peptides
- RecoveryKPVAnti-inflammatory tripeptide derived from α-MSH; gut and skin healing without sedation.
- PerformanceAnamorelinOral ghrelin-receptor agonist developed for cancer cachexia; approved in Japan as Adlumiz.
- PerformanceCapromorelinOral non-peptide ghrelin-receptor agonist; FDA-approved as a veterinary appetite stimulant.
See also
Educational use only
This calculator is provided for research and educational purposes. Outputs are derived from the values you enter. Always verify your math and consult a licensed physician before acting on any result.