At a Glance
Quickcomparison
Dose Range
Capromorelin
3–30 mg
MK-677 (Ibutamoren)
10–25 mg
Frequency
Once daily
Administration
Oral (capsule or tablet)
Oral (capsule or liquid)
Cycle Length
4-6 weeks
8-12 weeks
Onset Speed
Moderate (1-2 weeks)
Evidence Level
Moderate human trials (Phase 1-2)
Efficacy
Benefitratings
GH & IGF-1 Stimulation
Physical Function
Oral Convenience
Muscle and body composition
Recovery and athletic performance
Sleep quality and metabolic health
Technical Data
Compoundspecifications
Molecular Formula
C28H35N5O4
Molecular Weight
505.6 g/mol
Half-Life
1-2.4 hours in humans
Bioavailability
Good oral bioavailability
CAS Number
193273-66-4
C27H36N4O5S
528.7 g/mol
4-6 hours (IGF-1 elevation persists ~24 hours)
High oral bioavailability
159634-47-6
Protocols
Dosingtiers
starting
3 mg
Twice daily
Initial weeks
One of the lower doses tested in the year-long study in older adults; raised growth hormone and IGF-1 [1].
standard
10 mg
Once daily at bedtime
Ongoing
A simple once-daily bedtime dose used in the human trial that improved lean body mass [1].
advanced
Up to 12 months in the trial
The highest daily amount studied in older adults, giving the largest gains in muscle mass and physical function [1].
2-4 weeks initial
Lower entry dose used in practice to limit water retention and appetite surge before titrating up.
25 mg
Studied up to 1-2 years
25 mg once-daily oral is the dose used in the randomized trial in healthy older adults; increased GH/IGF-1 and fat-free mass [1]. Most-studied dose [2].
Applications
Bestsuited for
Age-Related Muscle Wasting
Capromorelin showed significant improvements in physical function — including tandem walk and stair climb — in elderly adults, making it a strong candidate for combating sarcopenia.
Appetite Stimulation
As an FDA-approved veterinary appetite stimulant, capromorelin has extensive real-world evidence for boosting food intake and body weight in mammals.
Growth Hormone Research
One of the best-studied oral ghrelin agonists with human Phase 2 data, offering researchers a well-characterized tool for studying GH/IGF-1 pathways.
Older Adults (60+) Seeking Body Composition Improvements
MK-677 was designed for aging populations. It restores GH and IGF-1 to youthful levels, increases lean mass, and improves physical function in people over 60. A 2-year clinical trial showed a 1.1 kg gain in fat-free mass with only modest fat gain—ideal for maintaining strength in older age.
Athletes and Fitness Enthusiasts Wanting Recovery Support
Oral dosing makes MK-677 convenient for athletes. It enhances muscle protein synthesis, speeds recovery after intense training, and supports lean mass building without the hassle of injections.
People with Chronic Wasting or Protein Deficiency
Clinical trials show MK-677 helps treat protein-energy wasting in kidney disease and other conditions. It stimulates appetite (a feature in these populations) and preserves muscle tissue—making it useful for those losing mass despite good nutrition.
Safety Profile
Sideeffects
Common
Appetite stimulation
Fluid retention and weight gain
Uncommon
Joint and muscle aches
Fatigue or lethargy
Peripheral edema (swelling)
Serious
Hyperglycemia
Increased appetite
Mild water retention or edema
Elevated fasting glucose
Joint or muscle pain
Carpal tunnel syndrome or nerve compression symptoms
Mild nausea or digestive upset
Glucose dysregulation and diabetes risk
Research Status
Safety& evidence
FDA Status
FDA approved for this use
Safety Overview
Capromorelin was generally well-tolerated in Phase 2 human trials involving nearly 400 elderly participants. Most side effects were mild to moderate. Its FDA-approved veterinary use provides additional long-term safety data in mammalian species.
Contraindications
xActive cancer or history of cancer (GH may stimulate growth)
xUncontrolled diabetes or severe metabolic disorders
xSevere liver or kidney disease
xPregnancy and lactation
Research compound
MK-677 has been studied in hundreds of humans over 2+ years and is generally well tolerated. Most side effects are mild and manageable, especially with lower starting doses. The lack of injection requirement makes it safer than injectable GH in terms of infection risk and sterility concerns. However, it is not FDA approved and should be viewed as a research compound.
xUncontrolled diabetes or severe glucose dysregulation
xActive cancer or high cancer risk requiring caution with IGF-1 elevation
xPregnancy or breastfeeding
Decision Guide
Which isright for you?
Choose Capromorelin if...
Stimulating growth hormone production in elderly adults
Supporting appetite and weight gain in wasting conditions
Improving muscle mass and physical performance
Anti-aging and longevity optimization
Choose MK-677 (Ibutamoren) if...
Building lean muscle mass and strength
Improving overall body composition in aging adults
Enhancing athletic recovery and performance
Supporting metabolic health and fat loss