Side-by-side · Research reference
MK-677vsSelank
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 2Reviewed13/45 cited
BHuman-MechanisticDraft11/40 cited
MK-677
Oral GHS · Ibutamoren
Oral capsule · 1×/day
Selank
Anxiolytic + Cognitive · Russian Pharma
Intranasal · 2–3×/day during stress / cognitive demand
01Mechanism of Action
Parameter
MK-677
Selank
Primary target
Ghrelin receptor (GHS-R1a)Murphy 1998
Monoamine system (serotonin / GABA modulation) + immunomodulation via tuftsin domainZaderej 2014
Pathway
GHS-R1a → Gαq → Ca²⁺ → sustained GH pulses across 24 hrNass 2008
Tuftsin-derived immune signaling + CNS monoamine modulation → reduced anxiety + improved mood / cognitionMedvedev 2007
Downstream effect
Sustained GH + IGF-1 elevation; appetite stimulation; lean mass preservationNass 2008
Anxiolytic + cognitive enhancement; immunomodulation via increased IL-6 + IFN-γMedvedev 2007Zaderej 2014
Feedback intact?
Pulsatile pattern preserved despite long half-lifeMurphy 1998
No GABA-receptor binding; no dependence reportedMedvedev 2007
Origin
Non-peptide spiroindane-piperidine small molecule designed at MerckMurphy 1998
Synthetic 7-AA peptide derived from human tuftsin (immune-system tetrapeptide)Zaderej 2014
Antibody development
—
—
02Dosage Protocols
Parameter
MK-677
Selank
Standard dose
10–25 mg / day oralNass 2008
25 mg used in Nass 2008 elderly trial; 10–15 mg common community dose.
150–300 mcg / dose intranasalZaderej 2014
Frequency
Once daily, oral
2–3× per day during stress
Lower / starter dose
5 mg / day
75 mcg / dose
Evidence basis
Phase 2 trials (Nass 2008, Murphy 1998)Nass 2008Murphy 1998
Human-mechanistic + Russian clinical trialsMedvedev 2007
Duration
8–16 weeks per cycle (off-cycle to reset receptor sensitivity)
10–14 day cycles, repeated as needed
Reconstitution
Oral, no reconstitution
Pre-formulated nasal spray (commercial); research vial: bacteriostatic water
Timing
Pre-sleep preferred for natural GH pulse alignment
Morning + early afternoon preferred
Half-life
~24 hrNass 2008
Once-daily dosing covers 24 hours.
Short (minutes plasma); CNS effect lasts ~3 hr
04Side Effects & Safety
Parameter
MK-677
Selank
Increased appetite
Strong appetite increase via ghrelin agonism
—
Water retention
Mild edema, paresthesias
—
Cancer risk
Contraindicated in active malignancy (GH/IGF-1 axis)
—
Cardiovascular
No clear adverse signal in trials; congestive heart failure caution
—
Drowsiness
Common, especially during initial weeks
—
Pregnancy / OB
Avoid
Avoid — insufficient data
Nasal irritation
—
Mild burning or congestion (transient)
Cognitive impairment
—
None — opposite effect (enhancement)
Allergic reaction
—
Rare hypersensitivity
Long-term safety
—
Limited Western RCT data
Absolute Contraindications
MK-677
- ·Active malignancy
- ·Pregnancy / breastfeeding
- ·Disrupted hypothalamic-pituitary axis
- ·Congestive heart failure (caution)
Selank
- ·Pregnancy / breastfeeding
- ·Hypersensitivity to peptide
Relative Contraindications
MK-677
- ·Untreated diabetes
- ·Pre-diabetes
- ·Severe insulin resistance
Selank
- ·Active autoimmune disease (theoretical via immunomodulation)
05Administration Protocol
Parameter
MK-677
Selank
1. Form
Capsule or oral solution. No injection.
Pre-formulated nasal spray (commercial) or research vial reconstituted with bacteriostatic water.
2. Site
Oral. Take with or without food.
Intranasal — 1–3 sprays per nostril per dose. Tilt head slightly back.
3. Timing
Pre-sleep preferred — aligns with natural GH pulse.
Morning + early afternoon for cognitive demand; PRN for acute anxiety.
4. Storage
Capsule: room temp ≤25 °C, dry place.
Refrigerate after reconstitution; ≤30 days. Light-protected.
5. Caveat
Monitor HbA1c every 8–12 weeks during chronic use.
Avoid co-administration with strong sedatives or other anxiolytics initially.