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Peptide Therapy GuideClear peptide education

Understand the source comparison

Bioavailability Peptides Delivery Method: Route Comparison

Subcutaneous Injection 80–95% Direct diffusion into capillaries and lymphatics from interstitial tissue None (bypasses GI tract entirely) Requires sterile technique; injection site rotation needed Gold standard for research peptides. Predictable pharmacokineti

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This page preserves a source comparison for education. It does not add a rating, recommendation or clinical judgment.

  • Subcutaneous Injection
  • 80–95%
  • Direct diffusion into capillaries and lymphatics from interstitial tissue
  • None (bypasses GI tract entirely)
  • Requires sterile technique; injection site rotation needed
  • Gold standard for research peptides. Predictable pharmacokinetics and reproducible dosing
  • Intramuscular Injection
  • 85–98%
  • Absorption through highly vascularised muscle tissue
  • None
  • Deeper needle penetration; slightly higher pain threshold
  • Faster absorption than subcutaneous for large molecules; used when rapid onset matters
  • Oral (Unmodified)
  • <5%
  • Intestinal epithelial transport (limited by degradation)
  • Complete exposure to pepsin, trypsin, chymotrypsin
  • Gastric enzymes degrade most sequences before absorption
  • Not viable for most research peptides without chemical modification
  • Oral (Modified)
  • 0.4–10%
  • Enhanced by permeation enhancers (e.g., SNAC) or PEGylation
  • Partial enzymatic resistance
  • Requires proprietary formulation; still far lower than injection
  • Achievable but requires significant structural modification and dose escalation
  • Nasal
  • 10–30%
  • Absorption across nasal mucosa into systemic circulation
  • Minimal (bypasses GI tract and first-pass metabolism)
  • Limited to small peptides (<3,000 daltons); mucosal irritation possible
  • Useful for specific peptides like oxytocin; not universal
  • Transdermal
  • 5–15%
  • Passive diffusion through stratum corneum (requires penetration enhancers)
  • Molecular weight must be <500 daltons; skin barrier limits most peptides
  • Rarely viable for peptides due to size and polarity constraints