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MK-677 (Ibutamoren): FDA Status, Research and Uses

By Living+. Updated October 25, 2026.

Key takeaway

MK-677, also called ibutamoren, is an oral growth hormone secretagogue. It is a small molecule, not a peptide. It is not FDA approved, and FDA lists ibutamoren mesylate in compounding category 2 for significant safety risks, including possible heart failure. It was studied in older adults, obesity, hip fracture and Alzheimer's disease [1, 3, 5].

At a glance

Where it stands

Checked

Not a peptide. Included because it is often grouped with growth hormone peptides.

  • FDA approvedNoNo approved product
  • Pharmacy compounding (503A)Category 2503A category 2 since Sept 29, 2023, still listed on FDA's May 14, 2026 categories list. FDA's advisory committee voted 13 to 1 against adding it to the 503A bulks list on Oct 29, 2024.
  • Outsourcing facilities (503B)Category 2503B category 2 (significant safety risks) since Dec 29, 2022, per FDA's safety risk page; also listed on FDA's 503B categories list (updated March 21, 2025).
  • WADA (sport)ProhibitedS2.2.4 Growth hormone secretagogues (named: ibutamoren (MK-677))
Same data as the Status Tracker. Checked against 10 sources

Key facts

Class
Growth hormone secretagogue that activates ghrelin receptors [5]
Length
Not a peptide (small molecule) [5]
Half-life
Not established in FDA's review; one source calls a single dose long-acting (24 hours) [3]
Route in studies
Oral, once daily in human studies [3, 9]
First studied
1995 (first described by Merck researchers) [3, 7]

How it works

MK-677 is a non-peptide small molecule. It binds to and activates the ghrelin receptor. Through this receptor it can make the pituitary gland release growth hormone. FDA groups it with growth hormone secretagogues, a class that includes both peptide and non-peptide drugs that raise the body's own growth hormone [5].

Merck researchers first described the compound in 1995 while looking for a growth hormone secretagogue that could be taken by mouth. In rat pituitary cells and in dogs, it raised growth hormone with only modest effects on other hormones [7]. FDA reports that development was discontinued in 1999 [3].

In a trial in healthy adults aged 64 to 81, a daily dose raised 24-hour growth hormone and raised IGF-1, the hormone that growth hormone signals through, to levels seen in young adults in most people [3, 8]. A two-year trial in older adults found more fat-free mass but no gain in strength or function [9].

Higher growth hormone and IGF-1 levels may also explain some of its side effects. Trials reported higher blood sugar, lower insulin sensitivity, swelling and increased appetite [3, 9]. A hip fracture trial was stopped early because of a possible heart failure signal [10].

What the research shows

5 human trials1 animal study

  1. 2011Human trial

    Adunsky et al. 2011 (hip fracture, phase IIb)

    123 older adults recovering from hip fracture Randomized, double-blind, placebo-controlled, 24 weeks [10]

    IGF-1 rose by 51.4 ng/ml, but most physical function measures did not improve. The trial was stopped early for a possible heart failure signal [10].

    Read the study
  2. 2008Human trial

    Nass et al. 2008 (Annals of Internal Medicine)

    65 healthy adults aged 60 to 81 (per the paper; FDA's review lists 47 on MK-677 and 24 on placebo in year 1) Randomized, double-blind, placebo-controlled, modified-crossover, 2 years [9]

    MK-677 25 mg daily raised growth hormone and IGF-1 and increased fat-free mass. FDA notes strength and function did not change, and fasting glucose rose [3, 9].

    Read the study
  3. 2008Human trial

    Sevigny et al. 2008 (Alzheimer's disease)

    563 people with mild to moderate Alzheimer's disease Randomized, double-blind, placebo-controlled, 12 months [3, 11]

    MK-677 25 mg daily raised IGF-1 but did not slow Alzheimer's disease progression [3, 11].

    Read the study
  4. 1998Human trial

    Svensson et al. 1998 (obesity)

    Studied for body composition

    24 men with obesity aged 18 to 50 Randomized, double-blind, placebo-controlled, 8 weeks [3, 12]

    FDA notes an oral glucose tolerance test showed impaired glucose handling at 2 and 8 weeks [3, 12].

    Read the study
  5. 1996Human trial

    Chapman et al. 1996 (healthy older adults)

    Healthy adults aged 64 to 81 (placebo 10, 10 mg 12, 25 mg 10) Randomized, double-blind, placebo-controlled, two 14-day periods [3]

    Growth hormone rose in a dose-related way. At 25 mg daily, IGF-1 rose to young-adult levels in most people [3, 8].

    Read the study
  6. 1995Animal study

    Patchett et al. 1995 (discovery)

    Rat pituitary cells and dogs Lab and animal pharmacology [7]

    The compound released growth hormone in cell culture and raised growth hormone in dogs after oral doses [7].

    Read the study

Doses used in studies

Human trials used MK-677 by mouth once a day. The most common study dose was 25 mg daily, used in the older adult, hip fracture and Alzheimer's disease trials [9, 10, 11]. An earlier trial in healthy older adults compared 10 mg and 25 mg daily for 14-day periods [3].

Some studies FDA reviewed also used 5 mg, 10 mg and 50 mg daily for short periods [3]. MK-677 has no FDA-approved dose.

Dosing is set by a licensed provider.

Side effects and safety

MK-677 is not FDA approved, so there is no FDA label or boxed warning. FDA lists ibutamoren mesylate in category 2 because of the potential for congestive heart failure in certain patients [1].

In the hip fracture trial, 4 patients (6.5%) on MK-677 had heart failure compared with 1 (1.7%) on placebo, and the trial was stopped early [3, 10]. In the two-year older adult trial, the most frequent side effects were mild swelling of the lower legs, muscle pain and increased appetite. Fasting blood glucose rose and insulin sensitivity fell [3].

In the Alzheimer's disease trial, drug-related side effects were more common with MK-677 (35.5%) than placebo (23.9%), mainly fatigue, swelling, dizziness, headache and confusion. Blood glucose rose in 15.4% of patients on MK-677 compared with 4.6% on placebo [3]. At the 2024 advisory committee meeting, several members raised concerns about fluid retention, heart failure and high blood sugar [4].

Common questions

Is MK-677 a peptide?

No. FDA describes ibutamoren mesylate as the salt of a non-peptide small molecule that activates ghrelin receptors [5].

Is MK-677 FDA approved?

No. FDA states ibutamoren mesylate is not a component of an FDA-approved drug and has no USP or NF monograph [3].

Can pharmacies legally compound MK-677?

FDA lists ibutamoren mesylate in category 2 for both 503A pharmacies and 503B outsourcing facilities because of significant safety risks [1, 2]. In 2024, FDA advisers voted 13 to 1 against adding it to the 503A bulks list [4].

Is MK-677 banned in sports?

Yes. The WADA Prohibited List names ibutamoren (MK-677) as a growth hormone secretagogue under S2.2.4, banned at all times [6].

What are the side effects of MK-677?

Trials reported higher blood sugar, lower insulin sensitivity, leg swelling, muscle pain and increased appetite. A hip fracture trial was stopped early for a possible heart failure signal [3, 10].

Does MK-677 raise growth hormone?

In trials it raised growth hormone and IGF-1 levels in older adults [8, 9]. Higher IGF-1 did not improve most function measures after hip fracture [10].

Why was the MK-677 hip fracture trial stopped?

It was terminated early because of a safety signal of congestive heart failure in a limited number of patients [10].

Did MK-677 help Alzheimer's disease?

No. A 12-month trial in 563 people found no slowing of Alzheimer's disease progression despite higher IGF-1 [3, 11].

What doses of MK-677 were used in studies?

Most human trials used 25 mg by mouth once a day. Other studies used 5 mg to 50 mg daily for short periods [3, 9].

Sources

  1. FDA: Certain bulk drug substances for use in compounding that may present significant safety risks
  2. FDA: Bulk drug substances nominated for use in compounding under section 503A (updated May 14, 2026)
  3. FDA briefing document: evaluation of ibutamoren mesylate, PCAC meeting October 29, 2024
  4. FDA: Final summary minutes, PCAC meeting October 29, 2024
  5. FDA: Advisory committee participation waiver, PCAC October 29, 2024 (substance descriptions)
  6. WADA: 2026 Prohibited List (PDF)
  7. Patchett et al. 1995, Proc Natl Acad Sci USA (PubMed)
  8. Chapman et al. 1996, J Clin Endocrinol Metab (PubMed)
  9. Nass et al. 2008, Ann Intern Med (PubMed)
  10. Adunsky et al. 2011, Arch Gerontol Geriatr (PubMed)
  11. Sevigny et al. 2008, Neurology (PubMed)
  12. Svensson et al. 1998, J Clin Endocrinol Metab (PubMed)
  13. FDA: Bulk drug substances nominated for use in compounding under section 503B (updated March 21, 2025)
  14. WADA: Prohibited List resource page (2026 List in force)
  15. FDA warning letter on MK-677 sold online, December 12, 2025

Updated October 25, 2026. Educational information, not medical advice.