Side-by-side · Research reference
GHRP-2vsMK-677
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2Reviewed15/42 cited
BPhase 2Reviewed13/45 cited
GHRP-2
Hexapeptide GHRP · Phase 2 (clinical diagnostic)
SQ · Multiple sites · 1–3×/day
MK-677
Oral GHS · Ibutamoren
Oral capsule · 1×/day
01Mechanism of Action
Parameter
GHRP-2
MK-677
Primary target
Ghrelin receptor (GHS-R1a) on anterior pituitaryBowers 1990
Ghrelin receptor (GHS-R1a)Murphy 1998
Pathway
GHS-R1a → Gαq → Ca²⁺ → GH vesicle exocytosisBowers 2002
GHS-R1a → Gαq → Ca²⁺ → sustained GH pulses across 24 hrNass 2008
Downstream effect
Strong GH pulse + IGF-1 elevation; appetite increase via ghrelin agonismBowers 2002
Sustained GH + IGF-1 elevation; appetite stimulation; lean mass preservationNass 2008
Feedback intact?
Yes, with somatostatin feedback active
Pulsatile pattern preserved despite long half-lifeMurphy 1998
Origin
Synthetic hexapeptide; developed by Bowers/Tulane group in the 1980sBowers 1990
Non-peptide spiroindane-piperidine small molecule designed at MerckMurphy 1998
Antibody development
—
—
02Dosage Protocols
Parameter
GHRP-2
MK-677
Standard dose
100–300 mcg per injectionBowers 1990
10–25 mg / day oralNass 2008
25 mg used in Nass 2008 elderly trial; 10–15 mg common community dose.
Frequency
1–3× per day
Once daily, oral
Lower / starter dose
50 mcg per dose
5 mg / day
Evidence basis
Phase 2 + clinical diagnostic useBowers 1990
Phase 2 trials (Nass 2008, Murphy 1998)Nass 2008Murphy 1998
Duration
8–12 weeks on / 4 off (anecdotal)
8–16 weeks per cycle (off-cycle to reset receptor sensitivity)
Reconstitution
Bacteriostatic water
Oral, no reconstitution
Timing
Pre-sleep + fasted preferred
Pre-sleep preferred for natural GH pulse alignment
04Side Effects & Safety
Parameter
GHRP-2
MK-677
Prolactin elevation
Mild but measurable
—
Hunger
Strong appetite increase
—
Injection site reaction
Mild erythema
—
Cancer risk
Contraindicated in active malignancy
Contraindicated in active malignancy (GH/IGF-1 axis)
Pregnancy / OB
Avoid
Avoid
Increased appetite
—
Strong appetite increase via ghrelin agonism
Water retention
—
Mild edema, paresthesias
Cardiovascular
—
No clear adverse signal in trials; congestive heart failure caution
Drowsiness
—
Common, especially during initial weeks
Absolute Contraindications
GHRP-2
- ·Active malignancy
- ·Pregnancy / breastfeeding
MK-677
- ·Active malignancy
- ·Pregnancy / breastfeeding
- ·Disrupted hypothalamic-pituitary axis
- ·Congestive heart failure (caution)
Relative Contraindications
GHRP-2
- ·Untreated diabetes
MK-677
- ·Untreated diabetes
- ·Pre-diabetes
- ·Severe insulin resistance
05Administration Protocol
Parameter
GHRP-2
MK-677
1. Reconstitution
Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL.
Capsule or oral solution. No injection.
2. Injection site
SQ — abdomen or thigh. Rotate sites.
Oral. Take with or without food.
3. Timing
Pre-sleep + fasted preferred.
Pre-sleep preferred — aligns with natural GH pulse.
4. Storage
Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.
Capsule: room temp ≤25 °C, dry place.
5. Needle
29–31G, 4–8 mm insulin syringe.
Monitor HbA1c every 8–12 weeks during chronic use.
06Stack Synergy
GHRP-2
+ CJC-1295 (no DAC)
StrongGHRP-2 + CJC-1295-no-DAC is a higher-amplitude alternative to the ipamorelin + CJC-1295 stack. GHRP-2 produces a stronger pulse but with cortisol + prolactin signal — choose when maximum GH amplitude is the goal and the side-effect tolerance is acceptable.
- GHRP-2
- 100–200 mcg SQ · pre-sleep
- CJC-1295 (no DAC)
- 100 mcg SQ · same injection
- Primary benefit
- High-amplitude GH pulse, body composition
MK-677
— no documented stacks