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

> MK-677 (ibutamoren) facts: FDA compounding category 2 status, WADA status, human trials, doses used in studies and reported side effects.

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- Last updated: October 25, 2026
- Publisher: Living+

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].

## Regulatory status

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

- FDA approved: No
- 503A compounding: [Category 2 (significant safety concerns)](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks). 503A 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.
- 503B bulks list: [Category 2 (significant safety concerns)](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks). 503B 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 prohibited: [Yes](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf) (S2.2.4 Growth hormone secretagogues (named: ibutamoren (MK-677)))
- FDA drug shortage: [Not on the shortage list](https://api.fda.gov/drug/shortages.json?search=generic_name:%22ibutamoren%22)
- DEA schedule: [Not scheduled](https://www.deadiversion.usdoj.gov/schedules/orangebook/c_cs_alpha.pdf)
- Last verified: November 2, 2026

Checked against: [FDA: Certain bulk drug substances for use in compounding that may present significant safety risks](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks), [FDA: 503A categories list (updated May 14, 2026)](https://www.fda.gov/media/94155/download), [FDA: 503B categories list (updated March 21, 2025)](https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/PharmacyCompounding/UCM467374.pdf), [FDA briefing document: ibutamoren mesylate, PCAC October 29, 2024](https://www.fda.gov/media/182087/download), [FDA: Final summary minutes, PCAC October 29, 2024](https://www.fda.gov/media/185412/download), [WADA: 2026 Prohibited List (PDF)](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf), [FDA warning letter on MK-677 sold online (Dec 12, 2025)](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/dynamic-health-group-dba-sarms-america-719257-12122025), [openFDA Drugs@FDA query: ibutamoren (no matches)](https://api.fda.gov/drug/drugsfda.json?search=products.active_ingredients.name:%22ibutamoren%22), [openFDA drug shortages query: ibutamoren](https://api.fda.gov/drug/shortages.json?search=generic_name:%22ibutamoren%22), [DEA Diversion: Controlled Substances - Alphabetical Order](https://www.deadiversion.usdoj.gov/schedules/orangebook/c_cs_alpha.pdf)

## Key facts

- Class: Growth hormone secretagogue that activates ghrelin receptors [5]
- Amino-acid 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 used 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

| Study | Year | Participants | Design | Result | Link |
| --- | --- | --- | --- | --- | --- |
| Human trial: Adunsky et al. 2011 (hip fracture, phase IIb) | 2011 | 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]. | [Source](https://pubmed.ncbi.nlm.nih.gov/21067829/) |
| Human trial: Nass et al. 2008 (Annals of Internal Medicine) | 2008 | 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]. | [Source](https://pubmed.ncbi.nlm.nih.gov/18981485/) |
| Human trial: Sevigny et al. 2008 (Alzheimer's disease) | 2008 | 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]. | [Source](https://pubmed.ncbi.nlm.nih.gov/19015485/) |
| Human trial: Svensson et al. 1998 (obesity) | 1998 | 24 men with obesity aged 18 to 50 | Randomized, double-blind, placebo-controlled, 8 weeks [3, 12] | MK-677 was studied for body composition. FDA notes an oral glucose tolerance test showed impaired glucose handling at 2 and 8 weeks [3, 12]. | [Source](https://pubmed.ncbi.nlm.nih.gov/9467542/) |
| Human trial: Chapman et al. 1996 (healthy older adults) | 1996 | 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]. | [Source](https://pubmed.ncbi.nlm.nih.gov/8954023/) |
| Animal study: Patchett et al. 1995 (discovery) | 1995 | 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]. | [Source](https://pubmed.ncbi.nlm.nih.gov/7624358/) |

## 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].

- [FDA warning letter: MK-677 sold online as an unapproved new drug](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/dynamic-health-group-dba-sarms-america-719257-12122025) (2025-12-12)
- [FDA: Certain bulk drug substances for use in compounding that may present significant safety risks](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks) (2026-04-22)

## Legal and regulatory status

- 2026-05-14: FDA's updated 503A categories list still shows ibutamoren mesylate in category 2, substances that raise significant safety risks [2]. [Source](https://www.fda.gov/media/94155/download)
- 2026-04-22: FDA's safety risk page, updated this date, lists ibutamoren mesylate in category 2 for both 503A and 503B compounding [1]. [Source](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks)
- 2026-01-01: The WADA 2026 Prohibited List took effect. It names ibutamoren (MK-677) under S2.2.4 growth hormone secretagogues, banned at all times [6, 14]. [Source](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf)
- 2025-12-12: FDA sent a warning letter to a firm selling products online, including "MK-677 Ibutamoren," stating these products are unapproved new drugs [15]. [Source](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/dynamic-health-group-dba-sarms-america-719257-12122025)
- 2024-10-29: FDA's Pharmacy Compounding Advisory Committee voted 13 to 1 against placing ibutamoren mesylate on the 503A bulks list, agreeing with FDA's proposal [4]. [Source](https://www.fda.gov/media/185412/download)
- 2023-09-29: FDA added ibutamoren mesylate to 503A category 2 [1]. [Source](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks)
- 2022-12-29: FDA added ibutamoren mesylate to 503B category 2 for outsourcing facilities [1, 13]. [Source](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks)

See every peptide's status side by side in the [Peptide Status Tracker](https://livingpluspeptides.com/regulation/tracker/#row-mk-677).

## Frequently asked 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](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks)
2. [FDA: Bulk drug substances nominated for use in compounding under section 503A (updated May 14, 2026)](https://www.fda.gov/media/94155/download)
3. [FDA briefing document: evaluation of ibutamoren mesylate, PCAC meeting October 29, 2024](https://www.fda.gov/media/182087/download)
4. [FDA: Final summary minutes, PCAC meeting October 29, 2024](https://www.fda.gov/media/185412/download)
5. [FDA: Advisory committee participation waiver, PCAC October 29, 2024 (substance descriptions)](https://www.fda.gov/media/182648/download)
6. [WADA: 2026 Prohibited List (PDF)](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf)
7. [Patchett et al. 1995, Proc Natl Acad Sci USA (PubMed)](https://pubmed.ncbi.nlm.nih.gov/7624358/)
8. [Chapman et al. 1996, J Clin Endocrinol Metab (PubMed)](https://pubmed.ncbi.nlm.nih.gov/8954023/)
9. [Nass et al. 2008, Ann Intern Med (PubMed)](https://pubmed.ncbi.nlm.nih.gov/18981485/)
10. [Adunsky et al. 2011, Arch Gerontol Geriatr (PubMed)](https://pubmed.ncbi.nlm.nih.gov/21067829/)
11. [Sevigny et al. 2008, Neurology (PubMed)](https://pubmed.ncbi.nlm.nih.gov/19015485/)
12. [Svensson et al. 1998, J Clin Endocrinol Metab (PubMed)](https://pubmed.ncbi.nlm.nih.gov/9467542/)
13. [FDA: Bulk drug substances nominated for use in compounding under section 503B (updated March 21, 2025)](https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/PharmacyCompounding/UCM467374.pdf)
14. [WADA: Prohibited List resource page (2026 List in force)](https://www.wada-ama.org/en/resources/world-anti-doping-code-and-international-standards/prohibited-list)
15. [FDA warning letter on MK-677 sold online, December 12, 2025](https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/dynamic-health-group-dba-sarms-america-719257-12122025)

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