MK-677 (Ibutamoren)

GH secretagogue (oral, non-peptide)

Also known as: Ibutamoren, MK-0677, L-163,191, LUM-201

Tier 2, Investigational, human data

Studied in registered human trials with published pharmacokinetic data, but not approved. Dosing outside a trial protocol has no established safety margin.

Half-life

5.00 hours · human data · oral

CORRECTION: the widely circulated "~24 hour half-life" is NOT supported by any retrievable source and appears to originate from vendor marketing. Peer-reviewed sources describe a half-life of at least 5-6 hours ("over six hours"), noting a relatively long terminal half-life versus related compounds such as capromorelin, which enables once-daily dosing. Once-daily dosing works because of prolonged biological GH/IGF-1 effect, not because of 24-hour plasma persistence. Precise terminal t½ with confidence intervals was not located, treat as approximate.

Dosing

5000 - 25000 mcg

Doses studied in humans: 5 mg and 25 mg orally at bedtime for 7 days in healthy young men. 25 mg once daily is the standard research dose. Studies up to 2 years exist. The therapeutic window is not established for non-approved use.

Frequency

Once daily

Timing

Bedtime dosing was used in the pivotal 7-day crossover study.

Regulatory status

Not approved for human use in any indication. Investigated by Merck and later Lumos Pharma for paediatric GH deficiency. Prohibited at all times under WADA section S2. Not a lawful dietary supplement ingredient.

Evidence base

human clinical · confidence: medium

Safety

The most consistently reported adverse signal is a clinically important decrease in insulin sensitivity with elevated fasting glucose, a genuine concern for anyone with prediabetes or diabetes. Also documented: increased appetite, fluid retention and oedema, lethargy. Substantially elevates IGF-1, so not for use with active malignancy. Congestive heart failure was a concern in an elderly-population trial. Long-term safety beyond 2 years is unknown.

Sources