What Is Bioavailability?
Category: Pharmacology
The proportion of a substance that enters the bloodstream and is available to produce an active effect. Subcutaneous injection provides near-complete bioavailability for most peptides.
Detailed Explanation
Bioavailability refers to the fraction of an administered dose of a drug or substance that reaches systemic circulation in an unchanged form. It is a key pharmacokinetic parameter that determines how much of a substance actually produces its intended effect. For peptides, bioavailability varies significantly depending on the route of administration. Subcutaneous injection typically provides 80-100% bioavailability, while oral administration of most peptides results in very low bioavailability due to degradation in the digestive tract.
Practical Context
This is why most peptides are administered via subcutaneous injection rather than orally - the digestive system would break down the peptide before it could be absorbed. BPC-157 is a notable exception, showing some oral bioavailability in research. When choosing between administration routes, consider that injection provides the most reliable and predictable absorption, which is important for consistent dosing.
Frequently Asked Questions
Why can't most peptides be taken orally?
Most peptides are broken down by stomach acid and digestive enzymes before they can be absorbed. This results in very low oral bioavailability, making injection the preferred route.
Does injection site affect bioavailability?
For subcutaneous injection, the site generally does not significantly affect overall bioavailability. However, blood flow rates differ between sites, which can affect absorption speed.
Related Peptides
- BPC-157 - A pentadecapeptide derived from human gastric juice, known for tissue healing properties. (Dosage | Calculator)
- Semaglutide - A GLP-1 receptor agonist used for weight management and blood sugar control. (Dosage | Calculator)
Related Terms
- Subcutaneous Injection - An injection into the fatty tissue layer just beneath the skin. The most common administration method for peptides, typically using a 29-31 gauge insulin syringe at a 45-90 degree angle.
- Half-Life - The time it takes for half of a substance to be eliminated from the body. Determines dosing frequency - shorter half-life peptides need more frequent dosing.
- Dose-Response Curve - The relationship between the amount of peptide administered and the magnitude of its effect. Higher doses don't always mean better results and can sometimes cause diminishing returns.