IV vs IM vs SC
Three injection routes — intravenous, intramuscular, subcutaneous — with different absorption profiles.
The three primary parenteral (non-oral) injection routes differ in absorption rate. Intravenous (IV) delivers directly into the circulation — 100% bioavailability, fastest onset, but requires venous access. Intramuscular (IM) delivers into muscle tissue — high bioavailability, faster than SC, suitable for larger volumes. Subcutaneous (SC) delivers into fat just beneath the skin — slower absorption, suitable for self-administration of small volumes (insulin, GLP-1 agonists, GHRH analogues). Most research peptides use SC in published protocols because absorption is reproducible, dosing is simple, and the route is patient-friendly.
- GlossaryPhase 3
The penultimate stage of clinical drug development — large randomised trials testing efficacy and safety against existing standards of care.
- GlossaryPharmacokinetics
How the body absorbs, distributes, metabolises, and eliminates a compound — "what the body does to the drug."
- GlossaryPharmacodynamics
"What the drug does to the body" — the relationship between concentration and effect.