Ibutamoren mesylate (MK-677): FDA and compounding status

Quick answer

Ibutamoren mesylate (MK-677) is not an FDA-approved drug and is not on FDA's 503A Bulks List. Section 503A records it as "Category 2" (April 22, 2026) and section 503B as "Category 2" (April 22, 2026). No PCAC recommendation is on file and the committee is advisory; verified September 16, 2026.

By Peptides.NYC Editorial TeamPublished September 16, 2026

Verified against FDA's bulk substances page on September 16, 2026. Every field below links the document it came from.

Current status

Ibutamoren mesylate (MK-677)

FDA approval

Not FDA approved

Ibutamoren mesylate is not an FDA-approved drug. FDA has evaluated it only as a bulk drug substance nominated for use in compounding, and it is not among the six substances on the 503A Bulks List at 21 CFR 216.23(a).

Sources

FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks (503A and 503B category 2, plus "bulk drug substances nominated but withdrawn"), content current as of April 22, 2026 (U.S. Food and Drug Administration, retrieved 2026-09-16)
21 CFR 216.23(a), Bulk drug substances that can be used to compound drug products in accordance with section 503A of the FD&C Act (six substances, no peptides) (Office of the Federal Register, retrieved 2026-09-16)
FDA, Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act (U.S. Food and Drug Administration, retrieved 2026-09-16)

Section 503A

Category 2

As stated on the cited document, dated April 22, 2026.

FDA has identified significant safety risks with this substance. Compounding from it is the position FDA warns about, not one it is exercising discretion over.

Added to 503A category 2 on September 29, 2023.

Sources

FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks (503A and 503B category 2, plus "bulk drug substances nominated but withdrawn"), content current as of April 22, 2026 (U.S. Food and Drug Administration, retrieved 2026-09-16)
FDA, Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act, updated May 14, 2026 (U.S. Food and Drug Administration, retrieved 2026-09-16)

Section 503B

Category 2

As stated on the cited document, dated April 22, 2026.

FDA has identified significant safety risks with this substance. Compounding from it is the position FDA warns about, not one it is exercising discretion over.

Added to 503B category 2 on December 29, 2022.

Sources

FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks (503A and 503B category 2, plus "bulk drug substances nominated but withdrawn"), content current as of April 22, 2026 (U.S. Food and Drug Administration, retrieved 2026-09-16)
FDA, Bulk Drug Substances Nominated for Use in Compounding Under Section 503B of the FD&C Act, updated March 21, 2025 (U.S. Food and Drug Administration, retrieved 2026-09-16)

Verified against FDA's bulk substances page on September 16, 2026.

Timeline

Every dated event on file for Ibutamoren mesylate (MK-677), newest first, with the document it came from.

April 22, 2026Status change
FDA's bulk drug substances page, content current as of this date, continued to list ibutamoren mesylate in category 2 under the 503A and 503B interim policy.
Sources
- FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks (503A and 503B category 2, plus "bulk drug substances nominated but withdrawn"), content current as of April 22, 2026 (U.S. Food and Drug Administration, retrieved 2026-09-16)

Related guides

Frequently asked questions

Is Ibutamoren mesylate (MK-677) legal to compound?

On FDA's section 503A list, Ibutamoren mesylate (MK-677) is recorded as "Category 2" as of April 22, 2026. On FDA's section 503B list, Ibutamoren mesylate (MK-677) is recorded as "Category 2" as of April 22, 2026. Ibutamoren mesylate (MK-677) is not on FDA's 503A Bulks List: that list is established by notice-and-comment rulemaking, and none of the categories above is inclusion on it. Compounding is governed by federal and state law together, and a pharmacy or outsourcing facility answers to both. This page reports what FDA has published; it is not legal or medical advice.

Was Ibutamoren mesylate (MK-677) reviewed by PCAC?

This tracker cites no Pharmacy Compounding Advisory Committee record for Ibutamoren mesylate (MK-677). PCAC's role is advisory: FDA must still complete notice-and-comment rulemaking before anything is added to the 503A Bulks List.

Is Ibutamoren mesylate (MK-677) FDA-approved?

Disclaimer: This page is a record of what regulators have published about Ibutamoren mesylate (MK-677). It is for educational purposes only, it is not medical or legal advice, and it is not a recommendation to use or compound any substance. Regulatory status changes; check the linked primary sources and consult your healthcare provider.