Ibutamoren (MK-677): Side Effects
Known side effects, contraindications, and interactions
📌TL;DR
- •7 known side effects documented
- •4 mild, 2 moderate, 1 severe
- •4 contraindications listed
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Side Effects Severity Chart
Appetite stimulation is a direct consequence of GHS-R1a activation, the same receptor that mediates ghrelin's hunger-promoting effects. Reported in the majority of trial participants, typically most pronounced in the first weeks of treatment.
Mild, transient lower extremity edema is a GH-mediated effect related to sodium and fluid retention. Usually resolves within the first few months of treatment. More pronounced in elderly populations.
Fasting blood glucose increased by approximately 0.3 mmol/L (5 mg/dL) in the Nass et al. trial. GH-mediated insulin resistance may worsen glucose tolerance, particularly in prediabetic or elderly populations.
Reduced insulin sensitivity is a recognized effect of elevated GH and IGF-1 levels. May be clinically significant in populations with metabolic risk factors.
Mild muscle aches reported in some trial participants, typically transient and self-resolving.
Modest cortisol elevation observed, though levels typically remained within the normal physiological range. Clinical significance uncertain.
The Adunsky et al. hip fracture trial identified a higher CHF rate in the ibutamoren group (6.5% vs 1.7% placebo), leading to early trial termination. This risk appears concentrated in elderly patients with underlying cardiac vulnerability.
⛔Contraindications
- •History of or risk factors for congestive heart failure (identified safety signal in clinical trials)
- •Diabetes mellitus or prediabetes (MK-677 increases fasting glucose and reduces insulin sensitivity)
- •Active malignancy or history of cancer (elevated IGF-1 may promote tumor growth)
- •Not approved for human use; investigational compound only
⚠️Drug Interactions
- •Insulin and oral hypoglycemic agents: MK-677 may antagonize glucose-lowering effects through GH-mediated insulin resistance
- •Corticosteroids: Additive fluid retention risk; MK-677 already causes mild edema and cortisol elevation
- •Other GH-elevating therapies (GHRH analogs, recombinant GH): Potential for additive or synergistic GH/IGF-1 elevation; safety of combinations not established
Community-Reported Side Effects
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Based on 300+ community reports
View community protocolsSafety Overview#
The safety profile of ibutamoren (MK-677) is characterized primarily by clinical trial data from several phase 2 studies involving predominantly elderly populations. While MK-677 was generally tolerated for its intended GH-stimulating effects, significant safety concerns emerged that contributed to the termination of clinical development.
Common Side Effects#
Increased Appetite#
Appetite stimulation is the most frequently reported side effect and is a direct pharmacological consequence of GHS-R1a activation. The ghrelin receptor is a key mediator of hunger signaling in the hypothalamus. In the Nass et al. trial, increased appetite was reported by the majority of MK-677-treated participants and was most pronounced during the initial weeks of treatment.
Peripheral Edema#
Mild, transient lower extremity edema occurred in a significant proportion of participants across trials. This effect is mediated by GH-induced sodium and water retention and is consistent with the known effects of GH therapy. Edema was typically mild and self-resolving but was more pronounced in elderly subjects.
Metabolic Effects#
MK-677's most concerning non-cardiac effects relate to glucose metabolism:
- Fasting glucose elevation: Increased by approximately 0.3 mmol/L (5 mg/dL) on average in the Nass et al. trial
- HbA1c changes: Modest increases in glycated hemoglobin were observed
- Insulin sensitivity: Declined with MK-677 treatment, consistent with the known diabetogenic effects of GH excess
These metabolic effects raise particular concern for populations already at risk for type 2 diabetes.
Serious Safety Concerns#
Congestive Heart Failure#
The most significant safety signal emerged from the Adunsky et al. hip fracture recovery trial, which was terminated early because of increased CHF rates:
| Group | CHF Events | Rate |
|---|---|---|
| Ibutamoren 25 mg | 4 of 62 | 6.5% |
| Placebo | 1 of 61 | 1.7% |
The mechanism likely involves GH-mediated fluid retention in patients with subclinical cardiac dysfunction. While this signal was detected specifically in elderly hip fracture patients (a high-risk population), it raised sufficient concern to effectively end clinical development.
IGF-1 and Cancer Risk#
Sustained elevation of IGF-1 has been associated epidemiologically with increased risk of certain cancers, including breast, prostate, and colorectal cancers. While no clinical trial of MK-677 demonstrated increased cancer incidence, the trials were too small and too short to adequately assess this risk.
Drug Interactions#
Glucose-Lowering Medications#
MK-677's insulin-resistance-promoting effects may antagonize insulin, metformin, sulfonylureas, and other antidiabetic agents. Blood glucose monitoring would be essential in any diabetic patient receiving MK-677.
Fluid-Retaining Medications#
Corticosteroids and other medications associated with fluid retention may produce additive effects when combined with MK-677, increasing the risk of edema and potentially CHF.
Population-Specific Risks#
- Elderly patients: Highest risk population based on available data; CHF signal and metabolic effects are most concerning
- Patients with cardiac history: Fluid retention may exacerbate pre-existing cardiac conditions
- Diabetic or prediabetic patients: Glucose metabolism effects may worsen glycemic control
- Cancer survivors: Theoretical IGF-1-mediated cancer risk
Related Reading#
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Frequently Asked Questions About Ibutamoren (MK-677)
What are the most common side effects of Ibutamoren (MK-677)?
The most commonly reported side effects of Ibutamoren (MK-677) include increased appetite, peripheral edema, elevated fasting glucose, insulin resistance, transient muscle pain, elevated cortisol. Appetite stimulation is a direct consequence of GHS-R1a activation, the same receptor that mediates ghrelin's hunger-promoting effects. Reported in the majority of trial participants, typically most pronounced in the first weeks of treatment.. Most reported side effects are mild and transient based on available data.
Are there serious side effects associated with Ibutamoren (MK-677)?
Potentially serious side effects of Ibutamoren (MK-677) include congestive heart failure. The Adunsky et al. hip fracture trial identified a higher CHF rate in the ibutamoren group (6.5% vs 1.7% placebo), leading to early trial termination. This risk appears concentrated in elderly patients with underlying cardiac vulnerability.. Immediate medical attention should be sought if severe adverse effects occur.
Who should not use Ibutamoren (MK-677)?
Ibutamoren (MK-677) should be avoided in the following situations: History of or risk factors for congestive heart failure (identified safety signal in clinical trials); Diabetes mellitus or prediabetes (MK-677 increases fasting glucose and reduces insulin sensitivity); Active malignancy or history of cancer (elevated IGF-1 may promote tumor growth); Not approved for human use; investigational compound only. Always consult with a healthcare provider before considering any peptide for research purposes.
Does Ibutamoren (MK-677) interact with other medications?
Potential interactions have been identified with: Insulin and oral hypoglycemic agents: MK-677 may antagonize glucose-lowering effects through GH-mediated insulin resistance; Corticosteroids: Additive fluid retention risk; MK-677 already causes mild edema and cortisol elevation; Other GH-elevating therapies (GHRH analogs, recombinant GH): Potential for additive or synergistic GH/IGF-1 elevation; safety of combinations not established. Drug interaction studies for Ibutamoren (MK-677) are limited, so caution is advised when using alongside any medications. Consult a healthcare provider for specific guidance.
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Medical Disclaimer
This website is for educational and informational purposes only. The information provided is not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before using any peptide or supplement.