Dihexa vs Selank
Angiotensin IV-derived oligopeptide that potentiates hepatocyte growth factor to drive synaptogenesis and cognitive enhancement with extraordinary potency
A clever brain-boosting peptide derived from your immune system's natural tuftsin molecule—it calms anxiety and sharpens your mind without the drowsiness or addiction risks of traditional anti-anxiety medications [1][4].
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Dihexa
8–20 mg
Selank
900–2700 mcg/day
Frequency
Dihexa
Once daily
Selank
3 times daily
Administration
Dihexa
Oral (capsule/tablet)
Selank
Intranasal
Cycle length
Dihexa
4-6 weeks
Selank
14 days, repeatable after 1-3 weeks
Onset speed
Dihexa
Moderate (1-2 weeks)
Selank
Rapid (hours to days)
Evidence level
Dihexa
Preclinical only — animal and cell-culture studies; no human trials
Selank
Limited human trials
Benefit ratings
Cognitive
Healing & Recovery
Anti-Aging
Anxiety Relief
Cognitive Enhancement
Immune Support
Compound specifications
Dihexa
Molecular formula
C27H44N4O5
Molecular weight
504.7 g/mol
Half-life
~12 days (following IV administration in rats)
Bioavailability
Orally active and blood-brain barrier permeable — specific oral bioavailability percentage not published
CAS number
1401708-83-5
Selank
Molecular formula
C33H57N11O9
Molecular weight
751.9 g/mol
Half-life
2-3 minutes (plasma); effects last hours due to downstream signaling
Bioavailability
High intranasal absorption; near 100% subcutaneous
CAS number
129954-34-3
Dosing compared
Dihexa
Oral
5–8 mg
Once daily · 2–4 weeks
Lower starting amount reported in practice. Dihexa has no human clinical trials, so all amounts come from animal research and community use [2][4].
8–20 mg
Once daily · 4–6 weeks
Commonly reported daily range in practice for cognitive support [2][4].
20–45 mg
Once daily · 4–6 weeks, then reassess
Upper end of amounts reported in practice. No long-term human safety data exists, so this should be approached with caution [2][4].
Sublingual
5–15 mg
Once daily · 4–6 weeks
Held under the tongue as an alternative to swallowing; amounts reported in practice are similar to oral use [4].
Topical
5–15 mg in DMSO carrier
Once daily · 4–6 weeks
Applied to the skin in a DMSO solution to help absorption; used in practice as a non-oral option [4].
Selank
Intranasal
Registered label dose
900 mcg/day total (3 doses of 300 mcg)
2 drops in each nostril, 3 times daily · Registered label dose
The approved dose on the Russian registration (ЛРС-003338/09): 2 drops in each nostril, three times a day. At 75 mcg per drop that is 300 mcg per administration and 900 mcg across the day, taken as a 14-day course that can be repeated after 1-3 weeks [7]. Human evidence, registered label.
Highest dose studied
2,700 mcg/day total (3 doses of 900 mcg)
900 mcg (12 drops) 3 times daily · Highest dose studied
The top of the range the developing institute describes as optimal — single doses of 300-900 mcg, 900-2,700 mcg a day split across three administrations — and the dose used in the multicentre generalised-anxiety and neurasthenia trial, where 2,700 mcg/day was compared against medazepam 30 mg/day for 14 days [9]. Because the label caps a single administration at 2-3 drops per nostril, a 900 mcg dose is given as 2-3 drops per nostril with the rest 15 minutes later [7]. Human evidence, trial protocol.
Subcutaneous injection
Community suggestion — not a studied protocol
300-500 mcg per injection
Once daily · Community suggestion — not a studied protocol
Community-reported, not peer-reviewed. No human study has tested subcutaneous selank and the registered product is nasal drops only [7], so this range comes from community and clinical-practice reports rather than a trial — there is no published safety or effectiveness data behind it. Two things worth knowing before choosing the route. The nasal spray is absorbed almost completely, with 92.8% of the dose reaching the bloodstream within 30 seconds [7], so injecting is not a way to get more of the peptide in. And in mice, the injected and intranasal routes did not act the same: injection shifted GABA-receptor binding while the nasal route shifted NMDA-receptor binding instead, which the authors put down to how each route is absorbed and broken down [13]. That is animal work, and no one has checked whether the same split happens in people.
Best suited for
Dihexa
Age-Related Cognitive Decline
Dihexa directly addresses the synaptic loss that underlies age-related cognitive decline by building new functional synaptic connections in the hippocampus. Animal studies demonstrate restored spatial learning in aged rats, [6] making it a compelling candidate for combating memory loss associated with aging.
Neuroplasticity Enhancement
Unlike nootropics that work through neurotransmitter modulation, dihexa drives physical neuroplasticity — the formation of new dendritic spines and synapses. [6] This makes it ideal for individuals looking to enhance their brain's capacity for learning and adaptation at a structural level.
Neurodegenerative Disease Research
Preclinical evidence in APP/PS1 Alzheimer's mice and scopolamine-induced amnesia models [4][6] positions dihexa as a leading research compound for neurodegenerative disease. It is patented for potential use in Alzheimer's and Parkinson's diseases, with ongoing interest from the research community.
Advanced Nootropic Stacking
Dihexa's unique mechanism (HGF/c-Met potentiation) is complementary to most other nootropic mechanisms, making it an excellent addition to advanced cognitive enhancement protocols when combined with choline donors, racetams, or adaptogens.
Selank
Anxiety Without the Fog
If traditional anti-anxiety medications leave you feeling sedated, foggy, or 'not yourself,' Selank offers a refreshing alternative. It calms anxious thoughts while keeping your mind sharp—like turning down the volume on worry without muting your brain [1].
Cognitive Performers
Students, professionals, and anyone facing demanding mental tasks love Selank for its dual action. It simultaneously reduces performance anxiety while enhancing memory and focus—the best of both worlds when you need to think clearly under pressure [1][2].
Stress Resilience Seekers
Chronic stress wreaks havoc on your brain. Selank helps protect against stress-induced cognitive decline by supporting BDNF levels and modulating your stress response [2]. Think of it as building a buffer between you and life's daily pressures.
Natural Approach Enthusiasts
Derived from tuftsin—a natural peptide your own immune system produces—Selank appeals to those seeking more 'natural' solutions [4]. It works with your body's existing systems rather than overriding them like synthetic drugs.
Side effects
Dihexa
Common
- Headache
- Vivid dreams or altered sleep patterns
- Emotional sensitivity
- Mild fatigue during adjustment
Uncommon
- Gastrointestinal discomfort
Serious
- Theoretical oncogenic risk from c-Met activation
Selank
Common
- Nasal irritation
- Mild fatigue
- Mild headache
- Injection site redness
Uncommon
- Vivid dreams
- Dizziness
Serious
- Allergic reaction
Safety & evidence
Dihexa
Evidence level
Preclinical only — animal and cell-culture studies; no human trials
FDA status
Research compound
Safety overview
Dihexa has demonstrated a favorable safety profile in published animal studies, with no reported tumorigenic effects or organ toxicity at cognitive-enhancing doses. However, the compound has not undergone formal human clinical trials, and long-term safety data does not exist. [7] The primary theoretical safety concern is sustained activation of the HGF/c-Met proto-oncogenic pathway, which could theoretically promote tumor initiation or growth. [7] The extremely long half-life (~12 days) [6][7] raises additional concerns about compound accumulation with chronic daily dosing. Anecdotal reports from the nootropics community generally describe good tolerability at doses of 5-20 mg daily, with headaches and vivid dreams as the most commonly reported effects.
Contraindications
- Known or suspected malignancy — c-Met/HGF pathway activation may promote tumor growth
- Pregnancy and breastfeeding — no safety data available
- History of cancer, particularly HGF/c-Met-driven tumors (hepatocellular, gastric, lung)
- Severe hepatic impairment
Selank
Evidence level
Limited human trials
FDA status
Research compound
Safety overview
The safety record comes from small Russian trials, and the numbers are worth seeing. In the 62-person generalised-anxiety and neurasthenia trial, 30 people took selank at 2,700 mcg a day and 32 took medazepam 30 mg a day for 14 days; the two calmed anxiety about equally, and selank also reduced fatigue where the benzodiazepine did not [9]. A second trial of 60 people with phobic-anxiety and somatoform disorders compared it with phenazepam and reported a clear anxiolytic effect that lasted about a week after the last dose [3]. The registered label lists only two side effects — an unpleasant taste when the drops run from the nose into the throat, and allergic reactions in people sensitive to the ingredients — and records no cases of overdose, which it attributes to how fast the peptide breaks down [7]. Neither trial published a per-arm adverse-event rate, so there is no side-effect percentage to compare against placebo.
Contraindications
- Pregnancy or planning to become pregnant
- Currently breastfeeding
- Known allergy to peptide components
- Children and adolescents
- Severe psychiatric disorders requiring immediate intervention
Which is right for you?
Choose Dihexa if...
- Cognitive enhancement and memory consolidation in age-related decline
- Supporting neuroplasticity and new synaptic connection formation
- Research into neurodegenerative disease therapeutics (Alzheimer's, Parkinson's)
- Nootropic stacking for individuals seeking enhanced learning capacity
Choose Selank if...
- Anxiety relief without sedation
- Cognitive enhancement and focus
- Memory improvement
- Stress resilience