MEDICAL DISCLAIMER: Educational research guidelines only. Lyophilized peptides are investigational chemical compounds and are NOT approved for human consumption, diagnosis, or therapy. Consult a licensed physician before any research application.
Macimorelin Dosage Chart, Schedule & Reconstitution Protocol
Quickstart Highlights
Macimorelin (Macrilen, Ghryvelin) is an orally active GHS-R1a (ghrelin receptor) agonist used as a diagnostic test for adult growth hormone deficiency (AGHD). It mimics ghrelin at the pituitary and hypothalamus to provoke a sharp growth hormone (GH) release; a blunted response indicates deficiency. The dose is a single 0.5 mg/kg oral solution taken after an 8-hour fast, with blood drawn at 30, 45, 60 and 90 minutes. On the FDA label a peak GH below 2.8 ng/mL confirms AGHD (PMID 29860473). In validation and pivotal trials it matched the accuracy of the insulin tolerance test and arginine+GHRH while being simpler and safer (PMID 24834478). It is rapidly absorbed (Tmax ~0.5-0.75 h), has a terminal half-life near 4 hours, is cleared via CYP3A4, and prolongs QTc by about 11 msec. The subcutaneous reconstitution figures on this page are an educational measurement reference only; clinically it is swallowed as a one-time oral solution.
Reconstitute: Add 1 mL bacteriostatic water → 60 mg/mL concentration.
Typical dose: 0.5 mg/kg single oral dose (about 30-50 mg for most adults)
Easy measuring: At 60 mg/mL, 1 unit = 0.01 mL = 0.6 mg (600 mcg) on a U-100 insulin syringe.
Storage: Granule pouches are stored refrigerated at 2-8 °C, protected from light. The clinical product is reconstituted in plain water immediately before use and the oral solution must be administered within 30 minutes; it is single-use and not stored. For the educational subcutaneous model on this page, a reconstituted vial would be refrigerated at 2-8 °C, but in real practice the diagnostic solution is prepared fresh and discarded after the test.
Half-life: Terminal half-life about 4.1 hours; Tmax ~0.5-0.75 h, peak GH at 30-90 minutes; metabolized by CYP3A4, ~75% fecal excretion.
Route: Oral solution in real-world use (0.5 mg/kg, fasted, single dose); the subcutaneous reconstitution shown here is an educational measurement model only.
Status: FDA-approved 2017 (Macrilen) and EMA-approved 2019 (Ghryvelin) as a prescription-only diagnostic for adult GH deficiency; not a treatment or performance compound.
About Macimorelin
Macimorelin (Macrilen, Ghryvelin) is an orally active ghrelin / growth hormone secretagogue receptor (GHS-R1a) agonist approved as a diagnostic agent for adult growth hormone deficiency (AGHD). The established Macimorelin dosage is a single 0.5 mg/kg oral dose taken after at least an 8-hour fast, with venous blood drawn at 30, 45, 60 and 90 minutes to capture the peak stimulated growth hormone level [1]. In the real world this is a one-time, swallowed diagnostic test, not a repeated treatment course: clinically the granules are dissolved in plain drinking water to make a 0.5 mg/mL oral solution, so the subcutaneous reconstitution figures below are an educational measurement reference only, not the actual route of administration.\n\nThis guide models a 60 mg vial reconstituted with 1.0 mL of bacteriostatic water (60 mg/mL, 600 mcg per insulin-syringe unit) so the weight-based diagnostic dose maps cleanly onto a U-100 syringe: a 60 kg adult's 30 mg dose is about 50 units, a 70 kg adult's 35 mg dose is about 58 units, and an 80 kg adult's 40 mg dose is about 67 units. Because the test is given once, there is no titration schedule, so the rows below show representative body weights rather than escalating doses [1][2].\n\nFrequency: Single one-time dose for diagnostic testing, not a recurring protocol. Macimorelin is a prescription-only diagnostic agent; this page is educational and not medical advice.
Quick Protocol Navigation
Reconstitution Instruction & Mixing Step-by-Step
Lyophilized powder must be reconstituted carefully. Agitating peptide chains can shear disulfide bonds and render the peptide biologically inert.
Draw 1.0 mL of bacteriostatic water into a sterile syringe (educational subcutaneous model only).
Inject the water slowly down the inner wall of the 60 mg Macimorelin vial; avoid aiming the stream directly at the granules and do not shake vigorously.
Gently swirl or roll the vial until the solution is completely clear; the result is a 60 mg/mL concentration, equal to 600 mcg per insulin-syringe unit.
Because the dose is weight-based, draw the units that match the patient's weight at 0.5 mg/kg (for example 30 mg ≈ 50 units for a 60 kg adult, 35 mg ≈ 58 units for 70 kg, 40 mg ≈ 67 units for 80 kg) on a U-100 syringe.
Educational note: in real clinical use Macimorelin is NOT injected — one 60 mg pouch of granules is dissolved in 120 mL of plain water to make a 0.5 mg/mL oral solution, swallowed once after an 8-hour fast, and used within 30 minutes; the subcutaneous figures here are a measurement reference only.
Interactive Macimorelin Syringe Calculator
Currently visualizing the 60 mg vial reconstituted with 1 mL bacteriostatic water. Adjust the target dose to dynamically render syringe units.
Reconstitution Calculation: 60mg dry powder in 1mL water yields 60.00 mg/mL. To evaluate a 250mcg dose, pull to 0.4 units (0 syringe ticks).
U-100 Syringe Representation
Educational reference visual. Assumes standard U-100 insulin syringe where 1.0 mL volume = 100 units.
Titration & Dose Escalation Schedules
| Phase | Dose per injection | Units (per injection) |
|---|---|---|
| Adult ~60 kg — single diagnostic dose (0.5 mg/kg) | 30000 mcg (30 mg) | 50 units (0.50 mL) |
| Adult ~70 kg — single diagnostic dose (0.5 mg/kg) | 35000 mcg (35 mg) | 58 units (0.58 mL) |
| Adult ~80 kg — single diagnostic dose (0.5 mg/kg) | 40000 mcg (40 mg) | 67 units (0.67 mL) |
| Adult ~100 kg — single diagnostic dose (0.5 mg/kg) | 50000 mcg (50 mg) | 83 units (0.83 mL) |
Administration guidelines: Refer to guidelines | 1 mL Reconstitution
Research Supplies Quantity Planner
Scientific mathematical planning of syringes, bacteriostatic water and dry vials needed for extended research blocks using the 60 mg vial.
Peptide Vials (Macimorelin, 60 mg each):
- checkOne 60 mg vial per diagnostic test covers adults up to ~120 kg at the 0.5 mg/kg dose, so a single test uses 1 vial
- checkThis is a one-time diagnostic, not a multi-week course, so the usual 8/12/16-week totals do not apply (still 1 vial per test)
- checkIn real clinical use the 60 mg comes as a single pouch of granules dissolved in water, not as an injectable vial
Insulin Syringes (U-100):
- check1 syringe per test in the educational subcutaneous model (single administration)
- checkA 30-50 mg diagnostic dose equals about 50-83 units at 60 mg/mL, fitting on one U-100 syringe
- checkClinically the dose is swallowed as an oral solution, so no syringe is used in real-world testing; 8/12/16-week counts are not applicable
Bacteriostatic Water (30 mL bottles): Use 1 mL per 60 mg vial for reconstitution.
- check1 mL of bacteriostatic water per test in the educational model; one 30 mL bottle covers roughly 30 reconstitutions
- checkBecause the test is a single event, there is no per-week consumption; a single bottle far exceeds the needs of one test
- checkClinically the granules are dissolved in 120 mL of plain drinking water (not bacteriostatic water) to make the 0.5 mg/mL oral solution
Alcohol Swabs:
- check1-2 swabs per test for the educational subcutaneous model (vial top plus injection site)
- checkA box of 100 swabs covers dozens of educational demonstrations
- checkNo swabs are needed for the real oral test; the 8/12/16-week framing is shown only for site consistency
Mechanism of Action (MOA)
Macimorelin is a non-peptidic, orally bioavailable small molecule (a pseudo-tripeptide originally designated JMV1843 / AEZS-130) that acts as a potent agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), the same G-protein-coupled receptor activated by the endogenous hormone ghrelin [1][5]. By binding GHS-R1a on somatotroph cells of the anterior pituitary and on hypothalamic neurons, macimorelin triggers an intracellular signaling cascade that drives exocytosis of stored growth hormone (GH), producing a brisk, measurable rise in serum GH [1][5]. This pharmacology is the entire basis for its diagnostic use: in a person with an intact GH axis a single oral dose produces a robust GH surge, whereas a blunted or absent response signals adult growth hormone deficiency.\n\nPharmacokinetics: after a single 0.5 mg/kg oral dose, macimorelin is absorbed rapidly with a median time to peak plasma concentration (Tmax) of roughly 0.5-0.75 hours, and the stimulated GH peak occurs between 30 and 90 minutes, which is why the diagnostic blood samples are timed at 30, 45, 60 and 90 minutes [1][4]. The compound is eliminated with a mean terminal half-life of about 4.1 hours and is metabolized primarily by hepatic CYP3A4; excretion is predominantly fecal (approximately 75% of the absorbed dose) with a minor urinary component (approximately 10%) [1][4]. A phase 1 single-ascending-dose study found less than dose-proportional increases in exposure between 0.5 and 1.0 mg/kg and a comparable peak GH response at those two doses, supporting 0.5 mg/kg as the diagnostic dose [4].\n\nDiagnostic interpretation: on the FDA-approved label a maximally stimulated serum GH below 2.8 ng/mL across the four post-dose samples confirms AGHD [1]. The pivotal crossover trial against the insulin tolerance test (ITT) reported that a 5.1 ng/mL cutoff provided an excellent balance of sensitivity and specificity, illustrating that the chosen threshold influences classification [2]. A clinically relevant pharmacodynamic caveat is QT prolongation: macimorelin increases the corrected QT interval by approximately 11 msec, so concomitant QT-prolonging drugs are avoided, and strong CYP3A4 inducers can blunt exposure and cause false-positive (falsely deficient) results [1][4].\n\nRoute honesty: the real-world route is a single oral solution, made by dissolving 60 mg of granules in 120 mL of water (0.5 mg/mL) and drinking it after an 8-hour fast. The subcutaneous reconstitution scheme presented on this page is the educational measurement convention used across this site, not a clinically validated delivery method. Macimorelin is a one-time diagnostic agent and is not used as a treatment, anti-aging, or performance compound [1][6].
Clinical Trial Efficacy Highlights
- starGarcia and colleagues (2013, Journal of Clinical Endocrinology & Metabolism) conducted the original validation study of oral macimorelin (AEZS-130) at 0.5 mg/kg in 50 adults with confirmed GH deficiency and 48 matched controls across 11 U.S. centers, reporting a sensitivity of about 82% and specificity of about 92% at a GH cutoff of 2.7 ng/mL, with diagnostic discrimination comparable to arginine+GHRH (ROC area under the curve 0.99 vs 0.94, P = .29) [3].
- starGarcia, Biller, Korbonits and colleagues (2018, Journal of Clinical Endocrinology & Metabolism, 103(8):3083-3093) ran the pivotal multicenter, randomized, two-way crossover trial comparing macimorelin to the insulin tolerance test (ITT) and concluded that oral macimorelin is a simple, well-tolerated, reproducible, and safe diagnostic test for AGHD with accuracy comparable to the ITT, identifying a 5.1 ng/mL GH cutoff as providing an excellent balance of sensitivity and specificity [2].
- starThe FDA-approved MACRILEN prescribing information reports that, in the confirmatory study versus the insulin tolerance test, macimorelin and ITT were in complete agreement in 84% of all subjects and in 89% of subjects with a high pre-test likelihood of AGHD, supporting a peak stimulated GH below 2.8 ng/mL as the label threshold confirming deficiency [1].
- starKlaus and colleagues (2020, Growth Hormone & IGF Research) performed a phase 1 single-ascending-dose, randomized controlled study in 28 healthy adults (0.5, 1.0, and 2.0 mg/kg), reporting a Tmax of 0.5-0.75 hours, a terminal half-life near 3.5 hours at lower doses, peak GH concentrations of roughly 32-38 ng/mL at 0.5-1.0 mg/kg, and QTcF prolongation of 10-11 msec, with all doses well tolerated and only mild-to-moderate, self-resolving adverse events (most commonly headache) [4].
- starAgrawal and Garcia (2014, Expert Review of Molecular Diagnostics) reviewed the macimorelin-stimulated GH test and positioned it as a simpler and safer alternative to the insulin tolerance test for diagnosing adult GH deficiency, summarizing the receptor pharmacology and early clinical performance that supported its development [5].
- starRegulatory milestones reflect this evidence base: the FDA approved macimorelin (Macrilen) in December 2017 as the first oral diagnostic test for AGHD, and the European Medicines Agency granted marketing authorization (as Ghryvelin) in January 2019, both citing accuracy comparable to ITT with a more favorable safety and convenience profile [1][6].
Side Effects & Tolerability Profile
Clinical subjects transiently report mild side effects. Slowly escalating the titration dose represents the single most effective intervention to limit side effects.
- warningThe most common adverse reaction in clinical testing was dysgeusia (an altered or metallic taste), reported in about 4.5% of subjects; this is generally transient and self-limited [1].
- warningDizziness, headache, and fatigue each occurred in roughly 3.9% of subjects, and were mild to moderate and short-lived after the single dose [1][4].
- warningGastrointestinal and appetite-related effects were reported, including nausea (about 3.2%), hunger (about 3.2%), and diarrhea (about 1.9%), consistent with ghrelin-receptor activation [1].
- warningQT prolongation is the key safety signal: macimorelin increases the corrected QT interval by approximately 11 msec, so concomitant use with drugs that prolong QT (for example antipsychotics, fluoroquinolone antibiotics, and Class IA/III antiarrhythmics) should be avoided to limit arrhythmia risk [1][4].
- warningDrug interactions can compromise the test result: strong CYP3A4 inducers (rifampin, carbamazepine, phenytoin, St. John's wort, efavirenz) may lower macimorelin exposure and produce false-positive (falsely deficient) results and should be discontinued before testing; GH-axis drugs such as recombinant GH, somatostatin analogs, glucocorticoids, and insulin should be managed/withheld appropriately beforehand [1].
- warningFalse-negative results can occur in patients with recent-onset (early) hypothalamic disease, in whom pituitary somatotrophs may still respond; repeat or alternative testing may be warranted in this setting [1].
- warningRoute note: the figures here model a subcutaneous injection for measurement consistency, but macimorelin is given clinically as a single oral solution; it is not an injectable or chronically dosed product, and it is not a treatment for GH deficiency.
- warningRegulatory/clinical status: macimorelin is a prescription-only diagnostic approved by the FDA (2017, Macrilen) and EMA (2019, Ghryvelin) for AGHD diagnosis; it is administered once under medical supervision and is not approved or intended for therapeutic, anti-aging, or performance use [1][6].
Subcutaneous Injection Technique
Most research peptides require subcutaneous injection into fatty tissue. Never inject directly into a blood vessel or deep muscle tissue unless clinically detailed.
1. Site Selection
Common locations include the abdomen (2 inches from navel), outer upper arms, or thighs.
2. Sanitization
Thoroughly clean the selected site, stopper and vial top using 70% isopropyl alcohol prep swabs.
3. Angle & Push
Pinch the skin and insert the needle at a 45 to 90-degree angle. Depress plunger smoothly.
4. Site Rotation
Rotate injection sites continuously to avoid lipodystrophy or tissue scarring.
Frequently Asked Questions
What is the typical Macimorelin dosage?expand_more
The typical Macimorelin dosage is a single 0.5 mg/kg oral dose taken after fasting for at least 8 hours, which works out to roughly 30 mg for a 60 kg adult, 35 mg for a 70 kg adult, and 40 mg for an 80 kg adult. It is given only once as a diagnostic provocation test for adult growth hormone deficiency, not on a recurring schedule. Venous blood is drawn at 30, 45, 60 and 90 minutes after the dose, and a peak stimulated growth hormone below 2.8 ng/mL confirms deficiency on the FDA label. The subcutaneous unit figures on this page are an educational measurement reference; clinically the dose is swallowed as an oral solution.
Is Macimorelin FDA approved?expand_more
Yes. The FDA approved Macimorelin (brand name Macrilen) in December 2017 as the first oral diagnostic test for adult growth hormone deficiency. The European Medicines Agency followed in January 2019 (marketed in Europe as Ghryvelin). It is a prescription-only diagnostic agent administered once under medical supervision and is not approved for treatment, anti-aging, or performance/bodybuilding use. This page is educational and not medical advice.
How is Macimorelin reconstituted and administered?expand_more
Clinically, one 60 mg pouch of macimorelin granules is dissolved in 120 mL of plain water to make a 0.5 mg/mL oral solution, which is swallowed once after an 8-hour fast and must be used within 30 minutes of preparation. No injection is involved. For the educational subcutaneous model on this site, a 60 mg vial is mixed with 1.0 mL of bacteriostatic water to give 60 mg/mL (600 mcg per insulin-syringe unit); at that concentration a 30 mg dose is about 50 units and a 40 mg dose about 67 units on a U-100 syringe.
What is the half-life of Macimorelin?expand_more
After a single 0.5 mg/kg oral dose, macimorelin has a mean terminal elimination half-life of about 4.1 hours. It is absorbed quickly, reaching peak plasma levels around 0.5 to 0.75 hours, and the stimulated growth hormone peak occurs between 30 and 90 minutes, which is why blood is sampled at 30, 45, 60 and 90 minutes. Macimorelin is metabolized mainly by hepatic CYP3A4 and is excreted predominantly in the feces (about 75%), with a smaller urinary component (about 10%).
Can Macimorelin be stacked with other compounds?expand_more
No. Macimorelin is a one-time diagnostic test, not a treatment that is stacked or cycled. In fact, certain co-administered drugs interfere with the test: medicines that prolong the QT interval should be avoided because macimorelin itself prolongs QTc by roughly 11 msec, strong CYP3A4 inducers (such as rifampin, carbamazepine, phenytoin, St. John's wort and efavirenz) can blunt exposure and cause false-positive results and should be stopped beforehand, and growth-hormone-axis drugs (recombinant GH, somatostatin analogs, glucocorticoids, insulin) should be managed or withheld before testing under medical guidance.
Related Guides & Tools
Step-by-step references for reconstituting, measuring, and storing Macimorelin, plus the universal dosing calculator.
Academic References & Study Citations
MACRILEN (macimorelin) for oral solution — full FDA prescribing information, DailyMed (National Library of Medicine). Initial U.S. Approval 2017. View Scientific Paper →
Garcia JM, Biller BMK, Korbonits M, et al. Macimorelin as a Diagnostic Test for Adult GH Deficiency. J Clin Endocrinol Metab. 2018;103(8):3083-3093. View Scientific Paper →
Garcia JM, Swerdloff R, Wang C, et al. Macimorelin (AEZS-130)-stimulated growth hormone (GH) test: validation of a novel oral stimulation test for the diagnosis of adult GH deficiency. J Clin Endocrinol Metab. 2013;98(6):2422-2429. View Scientific Paper →
Klaus Z, et al. Safety, tolerability, pharmacokinetics, and pharmacodynamics of macimorelin in healthy adults: results of a single-dose, randomized controlled study. Growth Horm IGF Res. 2020;52:101321. View Scientific Paper →
Agrawal V, Garcia JM. The macimorelin-stimulated growth hormone test for adult growth hormone deficiency diagnosis. Expert Rev Mol Diagn. 2014;14(5):531-538. View Scientific Paper →
Aeterna Zentaris Receives European Marketing Clearance for Macimorelin (EMA marketing authorization for diagnosis of adult growth hormone deficiency), January 16, 2019. View Scientific Paper →
MACRILEN- macimorelin acetate granule, for solution — DailyMed label landing page (NLM). View Scientific Paper →