Glossary
Subcutaneous
Subcutaneous refers to the fatty tissue layer under the skin. Why it is the standard parenteral route in peptide animal studies, and the limits on its volume.
Subcutaneous (often shortened to SC, SQ or subQ) refers to delivery into the loose fatty and connective tissue that lies under the dermis and above the muscle. In the published peptide literature it is the parenteral route used most often in rodent and large-animal models, and it is also the route of the licensed peptide medicines on which research-grade analogs are based.
Absorption kinetics
Compared with muscle, this tissue has a limited blood supply, so uptake is slower and flatter than after intravenous or intramuscular delivery: the injected volume forms a depot that drains over minutes to hours. Molecules smaller than about 16 kDa are reported to pass directly into blood capillaries, while bigger ones are preferentially absorbed via the lymphatics, adding a further lag. The outcome is a lower peak and a longer measurable tail, and this is one reason why bioavailability via this route is generally high but seldom total.
The practical limit is volume. Only small aqueous volumes are usual, which moves concentration decisions back into the reconstitution calculation and makes U-100 syringe markings and the choice of needle gauge part of planning a study. Everything sold on this site is intended solely for laboratory research and must not be administered to humans.
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