MK-677 (Ibutamoren) vs PT-141 (Bremelanotide)
A detailed comparison to help you understand the differences and choose the right peptide for your research goals.
MK-677 (Ibutamoren)
MK-677, also known as Ibutamoren, is an orally active growth hormone secretagogue. Unlike peptides, it can be taken orally and has a long half-life, providing 24-hour GH elevation.
Full details →PT-141 (Bremelanotide)
PT-141, also known as Bremelanotide, is a synthetic peptide analog of alpha-melanocyte-stimulating hormone. It is the only FDA-approved treatment for hypoactive sexual desire disorder (HSDD) in premenopausal women.
Full details →Side-by-Side Comparison
| Aspect | MK-677 (Ibutamoren) | PT-141 (Bremelanotide) |
|---|---|---|
| Mechanism | Acts as a potent, selective agonist of the ghrelin receptor (GHS-R1a). Increases GH and IGF-1 levels without affecting cortisol. Mimics ghrelin's GH-releasing effects. | PT-141 activates melanocortin receptors (MC3R and MC4R) in the central nervous system, particularly in areas associated with sexual arousal. Unlike PDE5 inhibitors, it works through the nervous system rather than the vascular system. |
| Typical Dosage | Typical dosing: 10-25mg taken orally once daily. Often taken at night due to sleep benefits and appetite increase. | FDA-approved dose: 1.75mg administered subcutaneously at least 45 minutes before anticipated sexual activity. Not to be used more than once within 24 hours or more than 8 times per month. |
| Administration | Oral administration (capsule or liquid). Can be taken with or without food. Long half-life allows once-daily dosing. | Subcutaneous injection in the abdomen. Available as Vyleesi (commercial product). Research use may involve different dosing protocols. |
| Side Effects | Increased appetite and water retention are most common. May cause lethargy, vivid dreams, and mild numbness. Can affect blood glucose and insulin sensitivity. | Common side effects include nausea (40% of users), flushing, headache, and injection site reactions. Transient blood pressure increases may occur. |
| Best For |
What They Have in Common
Both MK-677 (Ibutamoren) and PT-141 (Bremelanotide) are commonly used for: