# CJC-1295 DAC vs No-DAC: The Research Literature Compared > CJC-1295 DAC vs no-DAC in the research literature: the DAC variant's albumin conjugation gives a 5.8-8.1 day half-life; Modified GRF 1-29 (no-DAC) is short-acting. The distinction, cited. The DAC variant is albumin-conjugated, with an estimated 5.8-8.1 day half-life. The no-DAC form, Modified GRF 1-29, is short-acting. Two molecules, two pharmacokinetics — kept apart. ## What the DAC vs No-DAC Distinction Actually Is CJC-1295 DAC vs no-DAC is the same tetrasubstituted GHRH(1-29) peptide carrying — or lacking — one extra piece of chemistry, and that one piece changes the half-life from minutes to days. It is the single most-conflated point in the literature, and getting it right is the reason this page exists. Both forms share the four protease-resistant substitutions (D-Ala2, Gln8, Ala15, Leu27) that block the enzymes which clear native GHRH [2]. The **DAC** ('Drug Affinity Complex') variant adds a maleimidopropionyl linker on a C-terminal lysine that undergoes a covalent reaction with the free thiol on Cys34 of circulating serum albumin, forming a peptide-albumin conjugate [2]. Because albumin itself persists in blood for many days, the conjugate's half-life is dragged toward albumin's — the multi-day, long-acting form. The **no-DAC** form keeps the four substitutions but has no albumin-binding moiety, so it clears on the timescale of the underlying GHRH(1-29) peptide: short-acting. The two-channel comparison below is staged deliberately as two parallel tracks so the variants never blur together. ## Half-Life: DAC (5.8-8.1 days) vs No-DAC (minutes to hours) The CJC-1295 half life is where the DAC and no-DAC forms diverge most sharply, and it is the number to anchor on. For the DAC variant, the estimated half-life in healthy adults is 5.8 to 8.1 days, and after multiple doses IGF-1 elevation persisted up to 28 days [1]. In rats, the unconjugated-versus-conjugated contrast was already visible: the albumin conjugate produced a four-fold GH AUC increase over the unmodified peptide and remained detectable in plasma beyond 72 hours [2]. For the no-DAC form, the half-life is in the minutes-to-hours range — it reflects native GHRH(1-29) clearance, slowed by the protease-resistant substitutions but not extended by albumin binding [12]. A single DAC dose elevates GH and IGF-1 for days; a no-DAC dose produces a brief, pulse-like GH release. Treating a 'protocol' written for one as if it applied to the other is the practical error this distinction prevents. ## Modified GRF 1-29 (No-DAC): Why It Is Short-Acting Modified GRF 1-29 is the no-DAC sibling of CJC-1295 — the tetrasubstituted GHRH(1-29) sequence without the albumin-binding DAC moiety, and it is short-acting for one structural reason: nothing tethers it to a long-lived carrier protein. The four substitutions it shares with the DAC form do real work. They block dipeptidylpeptidase-IV and oxidative degradation, so Modified GRF 1-29 survives longer than truly native GHRH(1-29) [2]. But survival measured against native GHRH is still survival on the order of minutes to hours, not days [12]. Without the maleimidopropionyl-albumin conjugation, there is no mechanism to extend residence into the multi-day range. That is the whole pharmacokinetic difference: the DAC handle, present or absent. Community and clinic 'protocols' for Modified GRF 1-29 commonly cite 100-300 ug fixed doses, but these are not derived from controlled human trials [12]. ## The PK Comparison, Side by Side Reduced to a table, the contrast is clean. The DAC variant: albumin-conjugated, half-life 5.8-8.1 days, exposure measured in days, the species the 2006 human studies actually characterized [1]. The no-DAC Modified GRF 1-29: not albumin-conjugated, half-life minutes to hours, exposure brief and pulse-like, the form most community dosing language is implicitly written about [12]. When a source says 'CJC-1295' without specifying DAC or no-DAC, it is usually impossible to know which pharmacokinetic profile is meant — which is exactly why this review insists on the label every time. The human pharmacokinetic numbers on [the published research](/research) page belong to the DAC variant unless stated otherwise. --- A scroll-told review of the CJC-1295 literature, read top to bottom in the order the evidence accrued — the DAC and no-DAC tracks kept apart, every figure logged to its study and the human gaps left visibly open; no clinic behind the rail and nothing here dispensed or for sale.