CJC-1295 Dosage: DAC vs No-DAC - Dosage Peptide

CJC-1295 Dosage: DAC vs No-DAC - Dosage Peptide CJC-1295 dosage: why DAC and no-DAC need completely different frequencies, with the reconstitution chart, syringe units and weekly totals for each. Search for “CJC-1295 dosage” and the answers you find will contradict each other violently: one page says 2 mg once a week, the next says 100 mcg every night. Both pages may be quoting their sources accurately — because “CJC-1295” is a name that has been attached to two chemically different molecules whose durations of action are not remotely comparable: one with a measured human half-life of 5.8–8.1 days, the other short-acting on a scale of minutes. This article answers the only research question that actually matters here: which molecule is in the vial, what does the published human literature document about its dosing, and where does the documented evidence stop and folklore begin? The confusion is not the reader’s fault. It is a genuine naming collision that entered the field around 2009–2010 and never got cleaned up. The original compound — the one that appears in peer-reviewed human trials, the one ConjuChem Inc. developed, the one the World Anti-Doping Agency names by number — is CJC-1295 with DAC. DAC stands for Drug Affinity Complex. It is a chemical appendage that makes the peptide bind covalently to circulating albumin, and it is the entire reason the molecule is interesting. Without the DAC, there is no long half-life, no sustained IGF-I elevation, and no weekly dosing. The second compound is what the research-chemical market calls CJC-1295 no-DAC — the same modified 29–amino acid peptide backbone with the albumin-binding linker simply left off. This molecule already had a name before anyone called it CJC-1295: Modified GRF(1-29), usually written Mod GRF(1-29). It is not a slow-release version of anything. It is a short-acting secretagogue whose action is measured in minutes. So when a forum post, a vendor page, or an AI summary says “CJC-1295 is dosed at X,” the statement is meaningless without the DAC qualifier. The two molecules are not interchangeable at any dose, on any schedule, for any purpose. They produce different endocrine profiles by design. Getting the distinction wrong is not a rounding error — it is the difference between a once-weekly compound and a nightly one. ConjuChem’s medicinal chemistry program screened several maleimido derivatives of human growth hormone-releasing factor, hGRF(1-29). The paper that named CJC-1295 — Jetté and colleagues in Endocrinology, 2005 — identifies CJC-1295 explicitly as the tetrasubstituted form of hGRF(1-29) carrying an added Nε-3-maleimidopropionamide derivative of lysine at the C-terminus[1]. Read that carefully: in the primary literature, the maleimide linker is part of the definition of CJC-1295. The compound the market calls “CJC-1295 without DAC” is, by the naming convention of the paper that coined the name, not CJC-1295 at all — it is the tetrasubstituted GRF(1-29) intermediate. The date the collision began is actually documentable, which is more than most of this topic can say. FDA’s 2024 evaluation of these substances notes that CJC-1295 DAC was first described in 2005, and that a linker-free version first surfaces in the scientific literature in a 2010 report describing a preparation seized by Norwegian police and customs authorities in 2009 — a preparation whose mass spectrometric data matched the CJC-1295 sequence but which did not contain DAC. FDA states plainly that this “appears to be the first reference to CJC-1295 without DAC in the literature”[11]. In other words, the no-DAC molecule entered the record not as a published research compound but as a black-market product carrying a borrowed name. That is the root of the mess. Someone took the recognisable number and applied it to the cheaper, simpler intermediate, appended “no DAC” as a disclaimer, and the internet did the rest. Sixteen years later, half the dosing advice online is describing one molecule using the other molecule’s name — and the collision is now baked into US regulatory text. When FDA evaluated these compounds in 2024, it had to enumerate five separate bulk drug substances across two distinct active moieties: “CJC-1295 (free base)” and “CJC-1295 acetate” for the no-DAC molecule, and “CJC-1295 DAC (free base),” “CJC-1295 DAC acetate” and “CJC-1295 DAC trifluoroacetate” for the DAC one[11]. When a regulator has to spell out which “CJC-1295” it means before it can evaluate anything, the name is no longer doing its job. Our companion explainer on what CJC-1295 DAC and no-DAC actually are as molecules walks through the chemistry in more detail. To read the dosing literature honestly you need to know what problem CJC-1295 was built to solve, because the design constraints explain every number in this article. Growth hormone-releasing hormone (GHRH) is a hypothalamic peptide that acts on the GHRH receptor on pituitary somatotrophs to trigger growth hormone (GH) synthesis and release. Its biologically active fragment is the first 29 amino acids, GRF(1-29) — the molecule marketed pharmaceutically as sermorelin. GRF(1-29) works, but it is almost useless as a drug for one reason: it is destroyed almost immediately in plasma. Dipeptidyl peptidase-IV (DPP-4) cleaves the N-terminal dipeptide within minutes, and renal clearance handles the rest. Jetté’s own rat data illustrate the scale of the problem: after subcutaneous injection, native GHRH(1-29) was detectable in plasma for only about one hour, whereas CJC-1295 DAC remained detectable beyond 72 hours[1]. That is why sermorelin-type agents were confined to diagnostic testing and daily paediatric dosing rather than sustained endocrine therapy. Two engineering strategies were pursued against that problem, and they map exactly onto the two molecules in this article. Four amino acid substitutions were introduced into the GRF(1-29) backbone. FDA’s evaluation states them precisely: positions 2, 8, 15 and 27 of GHRH(1-29), natively L-alanine, L-asparagine, L-glycine and L-methionine, were substituted to D-alanine, L-glutamine, L-alanine and L-leucine respectively[11]. Three of those four are stability jobs. One is not, and being precise about that matters, because almost every explainer online asserts otherwise. D-Ala2 — the important one for stability. DPP-4 cleaves after position 2, and swapping the natural L-amino acid for its D-enantiomer makes that bond a poor substrate. FDA supports this point with the general finding that peptides carrying D-alanine in that position have been shown to be resistant to DPP-IV[11]. Gln8 — replaces an asparagine, per the authors, to overcome potential asparagine rearrangement or amide hydrolysis to aspartate, i.e. deamidation[11]. Leu27 — replaces the sole methionine, intended to prevent methionine oxidation[11]. Ala15 — not a degradation fix at all. Position 15 is a glycine in native GRF(1-29), twelve residues away from the only methionine, and neither Jetté nor FDA’s review ties it to any degradation liability[11]. Substituting a helix-favouring alanine at that position is a potency modification of a kind long documented in the GRF structure–activity literature — it raises GH-releasing potency in isolated pituitary cells, an assay that reflects receptor affinity rather than pharmacokinetics. It is bundled in with three stability modifications and then routinely described as though it were one of them. So the tetrasubstituted core is three stability modifications plus one potency modification, bundled together and usually described as though all four were the same kind of fix. Together they produce the tetrasubstituted GRF(1-29) — the molecule sold as Mod GRF(1-29) or “CJC-1295 no-DAC.” Here is a citation trap worth flagging, because it is the same failure this article exists to warn about. Jetté’s paper is frequently quoted for DPP-4 resistance of the tetrasubstituted peptide. What the paper actually says is: “All three human serum albumin conjugates showed enhanced in vitro stability against dipeptidylpeptidase-IV”[1]. That measurement was made on the DAC-bearing conjugates, not on the bare no-DAC intermediate. DPP-4 resistance for the no-DAC molecule follows from the chemistry of the D-Ala2 substitution, which is well established for peptides generally — it is not something that paper measured for that molecule. A DAC result quietly supporting a no-DAC claim is exactly how this whole topic went wrong. Note also what backbone modification does and does not buy. It buys resistance to one protease. It does not stop renal filtration of a 3.4 kDa peptide. The result is a compound that survives longer than native GRF(1-29) — better, but still a pulse agent. The second strategy is the DAC. A maleimidopropionic acid group is attached via a lysine residue. Maleimide chemistry is thiol-selective: it reacts with free sulfhydryl groups. Circulating human serum albumin carries exactly one accessible free thiol, at cysteine-34. So when the peptide is injected subcutaneously, it finds albumin in the interstitium and plasma and forms a covalent bond to Cys34. The peptide is now a passenger on a 66 kDa carrier protein with a plasma half-life of about three weeks. It cannot be filtered by the glomerulus. It is sterically shielded from many proteases. Jetté and colleagues confirmed the mechanism directly: Western blot of plasma from a CJC-1295-injected rat showed CJC-1295 immunoreactivity on the albumin band, appearing after 15 minutes and still present beyond 24 hours[1]. That is not a slow-release formulation trick. It is a bioconjugation strategy. One honest caveat, and it is FDA’s, not ours. Jetté concluded that albumin bioconjugation accounts for CJC-1295 DAC’s greater stability. FDA’s reviewers note that direct evidence for that specific causal attribution is lacking: demonstrating that the half-life of CJC-1295 DAC is longer than that of CJC-1295 without the DAC modification is the experiment that would be needed, and it has not been published. FDA adds that the backbone substitutions themselves could have contributed to the observed stability, so “it remains to be determined the extent to which these amino acid substitutions contribute to the stability of CJC-1295 DAC”[11]. The albumin binding is measured. The long half-life is measured. The claim that the former causes the latter is a well-supported hypothesis that nobody has closed with a head-to-head comparison — worth knowing, given that this is the central premise of every DAC-versus-no-DAC explainer, including this one. CJC-1295 with DAC progressed into human trials. The ClinicalTrials.gov registry documents a ConjuChem-sponsored study, NCT00267527 — a multicentre, randomised, placebo-controlled, double-blind Phase 2 study of CJC-1295 administered for 12 weeks in HIV-infected patients with HIV-associated visceral obesity, with a registry enrolment estimate of 120 and a start date of December 2005. Its registry status is TERMINATED, with a completion date of September 2006[2]. The registry number understates the real exposure: FDA’s 2024 review reports that 192 subjects were actually enrolled and randomised[11]. We are going to be very disciplined about what follows, because the internet is not — in both directions. One camp asserts CJC-1295 killed someone; the other waves the event away. Both talk past a public record that actually exists. What is documented. Contemporaneous reporting from NAM/aidsmap documents that ConjuChem halted the lipodystrophy study on 17 July 2006 following the death of a study participant at a site in Argentina, describes the design — once-weekly injections with three-week dose escalation of 60, 90 and 120 mcg/kg in the low-dose arm and 60, 120 and 240 mcg/kg in the high-dose arm against placebo, then continuing for a further nine weeks — and states that at the time, the cause of death and its relationship to the study drug was being investigated[3]. Eighteen years later, FDA’s briefing document for its December 2024 advisory committee meeting put the same event into the regulatory record with more clinical detail. FDA states that “ConjuChem Biotechnology withdrew CJC-1295 DAC from clinical trials in 2006 after the death of a subject involved in a phase 2 trial,” and describes it: two hours after receiving an eleventh weekly dose, one subject complained of chest discomfort, an ECG confirmed an acute myocardial infarction, and the subject died approximately one hour later. The attending physician’s stated most likely explanation was that the patient had asymptomatic coronary artery disease with plaque rupture and occlusion — that is, pre-existing disease rather than study drug. FDA also records that “the study was terminated, and the data from that study has not been published,” and that no further information about the other subjects or their adverse events was available[11]. What does not exist. A formal, published adjudication of drug causality. An attending physician’s opinion recorded in a secondary account is not a causality determination, and FDA itself characterises the underlying reports as anecdotal. Nor does the trial dataset exist in the public literature: 192 randomised patients, twelve weeks of dosing, and not one published table. The honest summary is therefore narrower than either camp claims. Development was discontinued in 2006 after a fatal myocardial infarction in a phase 2 trial. The treating physician attributed it to pre-existing coronary disease. No independent causality determination was ever published. The datas Both molecules are agonists at the same receptor. The differences are entirely pharmacokinetic — but pharmacokinetics is exactly what determines the endocrine output, which is why this matters more than it sounds. The GHRH receptor (GHRHR) is a class B G-protein-coupled receptor on pituitary somatotrophs. Agonist binding drives Gs–adenylate cyclase–cAMP–PKA signalling, which does two things: it triggers release of stored GH, and over longer exposures it increases GH gene transcription and somatotroph proliferation. That second effect is not theoretical — in GHRH-knockout mice, once-daily CJC-1295 increased total pituitary RNA and GH mRNA in a pattern the authors interpreted as somatotroph proliferation, confirmed by immunohistochemistry[4]. Hold on to that finding; it reappears later in this article wearing a much less flattering outfit. Critically, GHRH is not the only input. Somatostatin (SRIF) tonically inhibits GH release, and the alternation between GHRH drive and somatostatin brake is what produces the characteristic pulsatile GH profile. A GHRH agonist does not override somatostatin. It pushes against it. This has a direct dosing consequence that most protocol pages miss entirely: a GHRH analogue can only release GH when the somatostatin brake is off. During a somatostatin trough, the same dose produces a big pulse; during a somatostatin peak, it produces very little. This is the actual mechanistic reason behind the “dose at night” convention for the short-acting molecule, and it is a mechanistic rationale, not a demonstrated outcome. Give a short-acting GHRH analogue and you get a pulse: a sharp GH rise, peak within roughly 15–30 minutes, back toward baseline within one to two hours. The pituitary reloads. Endogenous rhythm is preserved because the drug is gone before the next natural pulse window. Give the DAC version and you get something structurally different: continuous, low-grade GHRH receptor occupancy for days. The key human finding here is Ionescu and Frohman’s 2006 study, which sampled GH every 20 minutes over a 12-hour overnight window before and one week after a single 60 or 90 mcg/kg CJC-1295 injection in healthy men aged 20–40. The result is more nuanced than either camp of the internet claims: pulsatility was preserved. The frequency and magnitude of GH secretory pulses were unaltered. What changed was the floor — basal (trough) GH rose 7.5-fold (p<0.0001), driving a 46% increase in mean GH (p<0.01) and a 45% increase in IGF-I (p<0.001). Notably, there was no significant difference between the 60 and 90 mcg/kg doses, and the IGF-I increases did not correlate with any parameter of GH secretion[5]. That last sentence is worth sitting with. The single most-repeated claim about CJC-1295 with DAC — that it “destroys natural pulsatility” and creates a flat bleed — is not what the human pulsatility study found. Pulses persisted; the trough rose. The equally common counter-claim — that it is simply a superior sustained version of the same thing — ignores that the trough elevation is precisely the non-physiological part, and that a dose increase from 60 to 90 mcg/kg bought nothing measurable. GHRH analogues and growth hormone secretagogues (GHS) such as ipamorelin, GHRP-2 and hexarelin act on different receptors — GHRHR versus the growth hormone secretagogue receptor GHS-R1a, the ghrelin receptor. The class-level observation, established in the GHS literature long before CJC-1295 existed, is that the effect of a GHS on GH release is synergistic with GHRH rather than merely additive, and that GHS remain only partially suppressed by inhibitory influences that nearly abolish the GHRH response. The synergy is not symmetric, and there is an elegant human experiment that proves it. In patients with a homozygous inactivating mutation of the GHRH receptor, intravenous hexarelin produced a complete absence of GH response — plasma GH stayed under 1 ng/mL, a 50- to 100-fold deviation from the normal response — while prolactin, ACTH and cortisol responses to hexarelin were normal[6]. The interpretation: an intact GHRH signalling system is required for a GHS to release GH at all. A ghrelin mimetic is not an independent GH lever; it is an amplifier of GHRH tone. That is the mechanistic case for the pairing, and it is a genuinely good one — but as we discuss below, a good mechanistic case is not a validated dose. Ipamorelin is the usual partner for a specific reason. Raun and colleagues characterised it as “the first selective growth hormone secretagogue”: it released GH from rat pituitary cells with potency and efficacy similar to GHRP-6, but — unlike GHRP-6 and GHRP-2, both of which raised ACTH and cortisol — ipamorelin did not release ACTH or cortisol at levels significantly different from GHRH stimulation, even at doses more than 200-fold above its ED50 for GH release[7]. That selectivity is why it displaced the older GHRPs in research pairings. This is the table the whole article exists to produce. Every figure in the “documented research protocol” rows reflects what our protocol pages document, not a recommendation; every half-life and endocrine-profile figure is sourced. Also called CJC-1295, DAC:GRF, CJC-1295 DAC Mod GRF(1-29), Modified GRF 1-29, tetrasubstituted GRF(1-29) Structure Tetrasubstituted hGRF(1-29) + Nε-3-maleimidopropionamide lysine at C-terminus[1] Tetrasubstituted hGRF(1-29), no linker Substitutions D-Ala2, Gln8, Ala15, Leu27 D-Ala2, Gln8, Ala15, Leu27 (identical) Binds albumin? Yes — covalently, at Cys34 No Half-life 5.8–8.1 days (estimated, human)[8] Short — minutes. Commonly quoted as ~30 min; not established by any published human PK study we or FDA could locate GH profile produced Sustained elevation: trough GH ↑7.5-fold, mean GH ↑46%, pulsatility preserved[5] Discrete pulse, peak ~15–30 min, back toward baseline within 1–2 h IGF-I duration after one dose 1.5–3× baseline for 9–11 days; up to 28 days above baseline after multiple doses[8] No comparable published multi-day IGF-I data Accumulates with repeat dosing? Yes — cumulative effect documented[8] No meaningful accumulation Documented protocol frequency Twice weekly Once daily (commonly before bed) Documented per-injection range 300–1,000 mcg 100–300 mcg Documented weekly total ~0.6–2 mg/week ~0.7–2.1 mg/week Typical reconstitution (5 mg vial) 2.0 mL → 2.5 mg/mL (2,500 mcg/mL) 3.0 mL → ~1.67 mg/mL (~1,670 mcg/mL) 1 unit on a U-100 syringe 25 mcg ~16.7 mcg Human data exists? Ascending-dose studies in 63 healthy adults across three papers; the one registered Phase 2 in patients was terminated with no published data[2][11] No human studies of any kind identified Regulatory status Neither is approved for human therapeutic use anywhere. Both are prohibited in sport at all times under WADA S2. Notice the trap hidden in the weekly-total row. The two molecules land at roughly the same milligrams per week — around 1–2 mg. That coincidence is why the naming collision persists undetected: someone reading “2 mg per week” can apply it to the wrong molecule and the total will look plausible. It is the distribution across the week that differs completely, and distribution is the whole pharmacology. Two 1,000 mcg DAC injections per week and seven 300 mcg no-DAC injections per week are approximately 2 mg either way, and they are not remotely the same intervention. Here is where we depart sharply from most pages on this keyword, because the honest answer is uncomfortable. The only substantial controlled dose-ranging human dataset on CJC-1295 is Teichman and colleagues, Journal of Clinical Endocrinology & Metabolism, March 2006 — one of three human studies in total, and the only one designed around dose. Design: two randomised, placebo-controlled, double-blind ascending-dose trials of 28 and 49 days, in healthy subjects aged 21–61, at two investigational sites. The first study gave one of four ascending single subcutaneous doses; the second gave two or three weekly or biweekly doses[8]. What it found, in the authors’ own terms: After a single injection, dose-dependent increases in mean plasma GH of 2- to 10-fold for 6 days or more. Mean plasma IGF-I increased 1.5- to 3-fold for 9–11 days. Estimated half-life of CJC-1295: 5.8–8.1 days. After multiple doses, mean IGF-I remained above baseline for up to 28 days, with evidence of a cumulative effect. No serious adverse reactions were reported. Administration was “safe and relatively well tolerated, particularly at doses of 30 or 60 mcg/kg.” That is the evidentiary bedrock of every CJC-1295 dosing claim in existence. Note what it is: a pharmacokinetic and pharmacodynamic study in healthy volunteers, 28–49 days long, with surrogate endocrine endpoints. It is not an efficacy study. It measured hormones, not outcomes. One word in that design description is doing more work than it can bear, and we are going to flag it rather than resolve it. The multiple-dose study administered “two or three weekly or biweekly doses.” “Biweekly” means both twice weekly and every two weeks, and the abstract does not disambiguate it. Given a 5.8–8.1 day half-life and a study designed around that half-life, the plain reading is every two weeks — but we are not going to resolve an ambiguity by guessing, in an article whose entire thesis is that frequency ambiguity is the problem. What can be said without guessing: no published trial administered CJC-1295 twice within a single week. Now do something the protocol pages never do — convert the trial’s weight-based doses into absolute micrograms and compare them to what the research community actually uses. This requires no cross-species extrapolation whatsoever; these were human doses in humans. Teichman 2006, best-tolerated doses[8] 30–60 mcg/kg 2,100–4,200 mcg Weekly, or the paper’s ambiguous “biweekly” Ionescu & Frohman 2006[5] 60 or 90 mcg/kg 4,200–6,300 mcg Single dose ConjuChem Phase 2 (terminated)[3] 60→120 mcg/kg escalating; 60→240 mcg/kg escalating 4,200–16,800 mcg Once weekly × 12 weeks Full published human range across all three studies[11] 30–250 mcg/kg 2,100–17,500 mcg Up to four SC injections; 73% received one Documented research protocols (this site’s DAC pages) 300–1,000 mcg fixed 300–1,000 mcg (≈4.3–14.3 mcg/kg) The gap is roughly 2- to 14-fold, and it points downward: the doses circulating in research protocols are substantially lower per injection than the doses the only real human PK trial singled out as well tolerated. (Run it yourself: 2,100 ÷ 1,000 = 2.1 at the narrow end; 4,200 ÷ 300 = 14 at the wide end.) This is the single most useful and least-reported fact about CJC-1295 dosing, and it cuts in two directions at once. On one hand, it is reassuring in the trivial sense: the community converged on doses below the studied range, not above it. On the other hand, it means that the community protocol is not the trial protocol. You cannot cite Teichman to justify 500 mcg twice weekly and then also cite Teichman’s 9–11 day IGF-I elevation as the expected effect — those are different doses. The 300–1,000 mcg twice-weekly convention has no published human PK or PD characterisation at all. It is an empirical folk convention that happens to fall in a conservative region relative to the studied doses. That is the accurate description, and it is much weaker than “clinically studied.” There is also a mechanistic argument buried in Ionescu & Frohman that deserves attention: 90 mcg/kg produced no significant additional response over 60 mcg/kg[5]. The GHRH receptor is saturable and somatostatin still applies the brake. Beyond some point, more CJC-1295 stops buying more GH and buys only more of the receptor-occupancy duration and whatever risk attaches to it. This is a reasonable inference from the published data, not a demonstrated dose-response ceiling for the sub-milligram range. We searched for controlled human trials of Mod GRF(1-29) / CJC-1295 no-DAC as a distinct entity. We did not find any, and neither did FDA: its 2024 literature review identified three human studies, all of CJC-1295 DAC, and it states that it identified no pharmacokinetic studies whatsoever of CJC-1295 free base or CJC-1295 acetate — the two no-DAC substances — nor any genotoxicity data for them[11]. There is no published human pharmacokinetic study establishing its half-life, no published dose-ranging study, no published efficacy trial. The ~30-minute half-life figure that appears on essentially every vendor page and every AI-generated summary is, as far as we can trace it, a repeated assertion rather than a citation to a measurement. What can be said honestly: the molecule is a GRF(1-29) analogue with a DPP-4-resistant substitution and no albumin anchor; native GRF(1-29) has a plasma half-life measured in minutes; the substitutions plausibly extend that somewhat but cannot alter renal clearance of a small peptide. A short half-life on the order of tens of minutes is therefore chemically reasonable. It is not documented. The distinction matters, because the entire justification for daily-and-sometimes-multiple-daily dosing rests on that number. With the evidence properly framed, here are the figures our protocol pages document, presented as documentation of what the research literature and research protocols reference — not as instruction. The reference protocol on our CJC-1295 DAC 5 mg vial dosage protocol page documents 300–1,000 mcg per injection, administered twice weekly, over an 8–12 week course. That works out to approximately 0.6–2 mg per week. The twice-weekly cadence is pharmacologically coherent given a 5.8–8.1 day half-life: dosing every 3–4 days means the second dose lands while roughly half the first is still conjugated to albumin, producing the smoothed steady-state the molecule was designed for. It is also worth noting that once-weekly at the same per-injection amount is equally defensible on half-life grounds, and that the twice-weekly convention is a community choice rather than a trial finding — no published trial administered this compound twice in a single week[8]. Concentration is a division problem, and it is the only calculation that matters: Concentration = total mass in vial ÷ volume of diluent added For a 5 mg vial with 2.0 mL of bacteriostatic water: 5 mg ÷ 2.0 mL = 2.5 mg/mL 2.5 mg/mL × 1,000 = 2,500 mcg/mL A U-100 insulin syringe is graduated so that 100 units = 1.0 mL, therefore 1 unit = 0.01 mL 2,500 mcg/mL × 0.01 mL = 25 mcg per unit Every dose is then dose ÷ 25: 300 mcg 0.12 mL 12 units 16 full doses 600 mcg ~8 weeks 400 mcg 0.16 mL 16 units 12 full doses 800 mcg ~6 weeks 500 mcg 0.20 mL 20 units 10 doses 1,000 mcg (1 mg) 5 weeks 750 mcg 0.30 mL 30 units 6 full doses 1,500 mcg ~3 weeks 1,000 mcg 0.40 mL 40 units 5 doses 2,000 mcg (2 mg) 2.5 weeks Sanity-check the extremes. At 500 mcg twice weekly the vial delivers exactly 10 doses = 5 weeks, so an 8–12 week documented course consumes roughly two to two-and-a-half 5 mg vials. At 1,000 mcg twice weekly the same vial is gone in 2.5 weeks and a 12-week course would consume nearly five vials. The 2.0 mL of diluent fits comfortably in a standard 3 mL lyophilisation vial with room to spare — the actual vial capacity should be confirmed before any diluent volume is chosen rather than assumed. This is where the arithmetic goes wrong most often. The 2 mg DAC vial protocol documents the same 300–1,000 mcg twice-weekly range — but reconstituted with the same 2.0 mL, it is a completely different concentration: 2 mg ÷ 2.0 mL = 1 mg/mL = 1,000 mcg/mL 1,000 mcg/mL × 0.01 mL = 10 mcg per unit That is 2.5× more dilute than the 5 mg vial at the same fill volume. Same drug, same dose, two-and-a-half times the units on the syringe: 30 units on the 5 mg vial = 750 mcg (2.5× intended) 50 units 50 units on the 5 mg vial = 1,250 mcg (2.5× intended) 100 units (a full syringe) 100 units on the 5 mg vial = 2,500 mcg (2.5× intended) The failure mode is obvious once it is laid out. Carry a unit count from a 2 mg vial across to a 5 mg vial reconstituted at the same 2.0 mL, and the same 50 units now corresponds to 1,250 mcg rather than 500 — a 2.5-fold error introduced by nothing but a change of vial. Units are not a dose. Units are a volume. The dose only exists once the concentration is known, and the concentration only exists once both the vial mass and the diluent volume are known. The concentration must therefore be