# CJC-1295 half life: the DAC and no-DAC pharmacokinetics > CJC-1295 half life: the DAC variant held an estimated 5.8-8.1 day half-life in healthy adults, with IGF-1 elevated up to 28 days. The no-DAC form is short-acting. A cited pharmacokinetic digest. The DAC variant's multi-day half-life is the molecule's defining property. Here is the number, the study behind it, and why the no-DAC form behaves completely differently. ## The headline number CJC-1295 half life, in the only place it has been measured in people, was an estimated **5.8-8.1 days** for the DAC variant in healthy adults [1]. That figure comes from a study dosing adults aged 21 to 61 with single and multiple subcutaneous doses of 30 or 60 micrograms per kilogram, and it is the source of essentially every half-life claim made for the molecule [1]. The duration is not abstract. Mean plasma GH stayed elevated 2- to 10-fold for six days or more, IGF-1 rose 1.5- to 3-fold for 9 to 11 days, and after multiple doses IGF-1 remained above baseline up to **28 days** [1]. A half-life measured in days is what lets a single dose move a hormone axis for weeks. This is the long-acting DAC form; the no-DAC form, below, is a different molecule kinetically. ## Why the half-life is so long Two pieces of engineering stack to produce the multi-day half-life. First, four substitutions block the proteases — chiefly dipeptidylpeptidase-IV — that clear native GHRH(1-29) in minutes [7][8]. Second, and decisively, the DAC modification covalently tethers the peptide to circulating serum albumin: a maleimidopropionyl linker on a C-terminal lysine binds the free thiol on Cys34 of albumin, so the peptide's residence time approaches albumin's own [2]. In rats, this bioconjugate produced roughly a 4-fold increase in GH exposure over two hours versus the unconjugated peptide, and remained detectable in plasma beyond 72 hours [2]. The effective circulating species is the large peptide-albumin complex, not the free peptide. PEGylation was explored elsewhere as an alternative half-life-extension strategy for GHRH analogs, which frames the problem albumin conjugation solved [10]. ## The no-DAC form is short-acting The no-DAC form — Modified GRF (1-29) — keeps the four substitutions but omits the albumin tether, so it is short-acting, with a duration in the minutes-to-hours range that reflects native GHRH(1-29) clearance modified only by protease resistance [12]. Early pharmacokinetic work established that synthetic GRF(1-29)NH2 has a short circulating half-life in healthy men, which is exactly why the long-acting analog program existed [9]. This is the single most important distinction in the CJC-1295 literature, and the one most often blurred: the DAC variant's half-life is measured in days; the no-DAC variant's is measured in minutes to hours. They are pharmacokinetically different molecules sharing a name. The full side-by-side is the [DAC vs no-DAC comparison](/dac-vs-no-dac). ## What a multi-day half-life does downstream A half-life of days does not just keep the parent peptide around; it changes the shape of the hormonal response. Because the DAC conjugate stimulates the GHRH receptor continuously, the foundational human study saw GH elevated for six days or more and IGF-1 for 9 to 11 days after a single dose, with IGF-1 staying above baseline up to 28 days after repeated dosing [1]. The downstream marker outlasts the dose by weeks. The striking part is what did not change. Under that sustained stimulation, the natural pulsatile pattern of GH secretion was preserved — basal GH rose roughly 7.5-fold and mean GH about 46% one week after a single dose, yet the frequency and magnitude of the GH pulses were unaltered [3]. A long half-life raised the floor without erasing the rhythm. In the GHRH-knockout mouse, the practical reading of the same property was that 2 micrograms once every 24 hours normalized growth, while spacing doses to every 48 to 72 hours was progressively less effective — the long duration makes a once-daily schedule sufficient in that model [4]. ## Reading half-life claims carefully Two cautions follow from the kinetics. First, any half-life figure for 'CJC-1295' is meaningful only with the form attached: 5.8-8.1 days describes the DAC variant, and quoting it for a no-DAC product is simply wrong [1][12]. Second, the human half-life rests on a small early-phase evidence base — the Teichman 2006 study and its companions — not on large pharmacokinetic trials, and CJC-1295 carries no approved human indication [1]. The analytical side of the literature is firmer: CJC-1295 has been definitively identified by high-resolution LC-MS/MS as the active ingredient in a seized 'GHRH' preparation, and detection assays for the molecule are well established [6]. The half-life that makes it a useful research analog is the same property that makes it detectable for a prolonged window in anti-doping contexts [6]. ## How long does CJC-1295 stay in the body? CJC-1295 DAC had an estimated half-life of 5.8-8.1 days in healthy adults, with IGF-1 elevation persisting up to 28 days after multiple doses; the no-DAC Modified GRF (1-29) form is short-acting, in the minutes-to-hours range [1][12]. So 'how long it stays' depends entirely on which form: the DAC variant lingers for days via albumin binding, while the no-DAC form clears quickly [2][12]. --- A marketplace-style listing of the published CJC-1295 record — the DAC and no-DAC forms shelved on separate channels, every figure tagged to its study, nothing here dispensed, prescribed, or for sale.