Half-Life
Half-life is the time required for the concentration of a peptide to decrease by 50%. It determines how frequently a peptide must be administered to maintain consistent levels in research protocols.
Overview
Half-life is a pharmacokinetic property — a feature of the compound and the biological system, not of the dose. A peptide with a short half-life (e.g., 30 minutes for Sermorelin) clears rapidly and may require twice-daily or more frequent administration to maintain consistent exposure. A peptide with a long half-life (e.g., 6–8 days for CJC-1295 with DAC) can be dosed weekly. Most natural endogenous peptides have very short half-lives (minutes), which is why synthetic analogues are often engineered with structural modifications (PEGylation, DAC attachment, amino acid substitutions) to extend their duration. Half-life is distinct from duration of action, which refers to how long biological effects persist.
Related Terms
Frequently asked questions
What is the half-life of BPC-157?+
BPC-157 has a relatively short half-life in plasma (estimated 30 minutes to a few hours), which is why twice-daily dosing is common in animal research protocols.
Does half-life change with dose?+
For most peptides following first-order kinetics, half-life is independent of dose — the same fraction clears in the same time regardless of concentration.
Is a longer half-life always better?+
Not necessarily. A longer half-life means convenient dosing but also means that if a side effect occurs, the compound stays in circulation longer. The ideal half-life depends on the research goal.