Half-Life
Half-life is the time it takes for half of a compound to break down or be cleared in a test system or study. It is a measured number from research, not a fixed feature of the molecule.
Where the word comes from
“Half-life” joins two plain English words, but the term was born in physics. Physicists in the early 1900s needed a way to describe radioactive decay: a decaying substance never quite reaches zero, so they timed how long it took for half of it to be gone. Chemistry and biology later borrowed the word for any process that declines the same way, including the breakdown of compounds measured in published studies.
What it means here
Natural peptides tend to break apart quickly, so chemists build modified versions and then measure whether the change made the molecule last longer in a study. For example, a published Phase 1 study of the GHRH analog CJC-1295 reported a half-life of about six to eight days. On our pages, any half-life number is a reported study measurement — context from the literature, never guidance.
Words you’ll see together
- plasma half-life — the version of the measurement reported from blood samples collected in a study
- terminal half-life — the value measured during the final decline phase of a study’s data
- clearance — a study measurement of how quickly a compound is removed from the test system
- albumin — a blood protein; some modified peptides bind it, which changes the value measured in studies
- pharmacokinetics — the field of science these measurements come from
Related terms
- Pharmacokinetics — the branch of science that half-life measurements come from
- Stability — how a compound holds up chemically outside a test system
- GHRH — a hormone whose lab-made analogs are designed to change this measurement
- Peptide — the class of molecule these measurements describe on our pages
Where it appears in our catalog
- CJC-1295 DAC — a modified analog whose measured half-life is reported in published work
- Sermorelin — a shorter GHRH analog studied alongside longer-lasting ones
- Comparing compounds — how measured properties like this differ across the catalog
References
- Teichman SL, Neale A, Lawrence B, Gagnon C, Castaigne JP, Frohman LA (2006). Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. J Clin Endocrinol Metab 91(3):799-805. PMID: 16352683
