Half-life

A compound's elimination half-life is the time it takes for its concentration in plasma to fall by half once absorption is complete. After five half-lives about 97% has been cleared, which is the usual rule of thumb for "gone". Half-life is the single number that most shapes how a peptide was dosed in the research literature: a compound cleared in minutes was given daily or more often, one cleared over days was given weekly.

The range across the profiles on this site is enormous. BPC-157 and ipamorelin have plasma half-lives under an hour. Semaglutide lasts about a week and retatrutide about six days, because both were engineered to bind albumin and resist enzymatic cleavage at the peptide bond. CJC-1295 with DAC shows the same trick applied to a growth-hormone-releasing peptide: the drug affinity complex extends a thirty-minute half-life to roughly a week.

Half-life describes clearance from blood, not duration of effect. Several short-lived peptides, BPC-157 among them, are reported to act well after they have left circulation, which each profile discusses under "Pharmacology". Every profile lists the literature's half-life figure in its quick facts.