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24d • Peptide Tips
Why Some Peptides Work as Nasal Sprays (And Most Don't)
This post is for educational purposes only and is not medical advice. Always consult with a healthcare provider before starting any new supplement or peptide protocol.
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You've probably seen nasal spray versions of popular peptides floating around. BPC-157 nasal spray, PT-141 nasal spray, even GLP-1 nasal sprays.
But here's the thing — just because something comes in a spray bottle doesn't mean your nose is the right delivery method.
Let me break down exactly how nasal sprays work, why they only make sense for certain peptides, and which ones actually belong in your nose.
How Your Nose Connects to Your Brain
Your nasal cavity isn't just an air filter. It's one of the few places in your body where the outside world has almost direct access to your central nervous system.
Here's the simple version:
Two key pathways exist in your nose:
- The Olfactory Nerve — The nerve responsible for smell. It runs from the top of your nasal cavity directly into your brain. No blood-brain barrier in the way.
- The Trigeminal Nerve — A large nerve that covers sensation in your face. It also has branches that reach into your brainstem.
When you spray something into your nose and it reaches these nerve pathways, it can essentially "hitch a ride" straight into your central nervous system.
This is called nose-to-brain delivery.
Why This Matters for Peptides
Most peptides you inject work systemically — they enter your bloodstream and travel throughout your body to do their job.
But some peptides specifically target:
- Your brain
- Your nervous system
- Receptors that are concentrated in neural tissue
For these peptides, nasal delivery can make a lot of sense because:
✅ Faster onset (bypasses digestion and first-pass liver metabolism)
✅ Direct access to the brain (skips the blood-brain barrier problem)
✅ Non-invasive (no needles)
The Key Question: Where Does This Peptide Need to Go?
Here's a simple framework:
If the peptide targets the brain or CNS → Nasal spray makes sense ✅
If the peptide targets nervous system receptors → Nasal spray makes sense ✅
If the peptide targets muscles, joints, gut, or fat tissue → Nasal spray doesn't make sense ❌
If the peptide needs systemic/whole-body effects → Nasal spray doesn't make sense ❌
Size Matters: The Dalton Factor
Here's something most people overlook — molecular size plays a huge role in whether a peptide can actually absorb through your nasal membrane.
Molecular weight is measured in Daltons (Da). Think of it like this:
- Smaller molecules = easier to slip through the nasal membrane
- Larger molecules = harder to absorb, more gets wasted
The general cutoffs:
Under 1,000 Da → Absorbs well through the nasal membrane
1,000 - 6,000 Da → Can work, but absorption decreases as size increases
Over 6,000 Da → Poor absorption without enhancement
Some real examples:
- Semax (~800 Da) — Small, absorbs efficiently ✅
- Selank (~750 Da) — Small, great nasal candidate ✅
- Oxytocin (~1,000 Da) — Right at the threshold, works well ✅
- PT-141 (~1,025 Da) — Just over 1k, still absorbs reasonably ✅
- VIP (~3,300 Da) — Larger but still within workable range ✅
- BPC-157 (~1,400 Da) — Could technically absorb, but why? Target isn't the brain ❌
- Semaglutide (~4,100 Da) — Getting large, plus needs sustained systemic levels ❌
- TB-500 (~4,900 Da) — Large molecule, systemic target ❌
The takeaway: Even if a peptide is small enough to absorb nasally, that doesn't mean nasal is the right delivery method. Size determines can it absorb — but the peptide's target determines should you bother.
Peptides That Actually Make Sense as Nasal Sprays
1. PT-141 (Bremelanotide)
- What it does: Works on melanocortin receptors in the brain to increase sexual arousal
- Why nasal works: Its target is literally your brain. The MC4R receptors it activates are in your hypothalamus.
- Note: The FDA-approved version (Vyleesi) is injectable, but nasal delivery has been studied and can work
2. Semax
- What it does: Neuroprotective, cognitive enhancement, derived from ACTH
- Why nasal works: Designed specifically for brain effects — memory, focus, mood
- Note: This is one of the OG nasal peptides, developed in Russia specifically as a nasal spray
3. Selank
- What it does: Anxiolytic (anti-anxiety), mood regulation, immune modulation
- Why nasal works: Targets GABA receptors and affects brain neurotransmitter balance
- Note: Also developed as a nasal spray from the start
4. Oxytocin
- What it does: The "bonding hormone" — affects social behavior, trust, emotional connection
- Why nasal works: Needs to reach the brain to influence behavior and mood
- Note: Extensively studied as intranasal for autism research and social anxiety
5. VIP (Vasoactive Intestinal Peptide)
- What it does: Regulates inflammation, supports circadian rhythm, neuroprotective effects
- Why nasal works: Targets receptors in the brain and nervous system, used in protocols for chronic inflammatory conditions and mold illness
- Note: Dr. Shoemaker's CIRS protocol specifically uses intranasal VIP for its direct CNS effects
Peptides That Don't Make Much Sense as Nasal Sprays
BPC-157
- Target: Gut healing, tendons, ligaments, systemic tissue repair
- Problem: You want this in your bloodstream reaching damaged tissues, not primarily your brain
- Better route: Subcutaneous injection or oral (for gut-specific effects)
GLP-1 Agonists (Semaglutide, Tirzepatide)
- Target: GLP-1 receptors in pancreas, gut, and brain (appetite centers)
- Problem: These are large molecules that need sustained systemic exposure. Nasal absorption is inconsistent and you'd lose the steady-state levels that make them effective.
- Better route: Subcutaneous injection
TB-500 (Thymosin Beta-4)
- Target: Tissue repair, wound healing, inflammation throughout the body
- Problem: Needs to circulate systemically to reach injury sites
- Better route: Subcutaneous or intramuscular injection
CJC-1295 / Ipamorelin (Growth Hormone Secretagogues)
- Target: Pituitary gland (to release GH) and systemic effects
- Problem: Needs reliable dosing and systemic absorption for consistent GH pulses
- Better route: Subcutaneous injection
The Bottom Line
Nasal spray delivery is a tool, not an upgrade.
It's specifically useful when:
- The peptide needs to reach your brain or nervous system
- You want faster onset for acute effects
- The peptide has been shown to absorb well through nasal mucosa
It's NOT automatically better just because it sounds more convenient.
If someone is selling you a nasal spray version of a peptide that works systemically on your body (not your brain), ask yourself: "Why would I want this to go to my brain instead of my bloodstream?"
If there's no good answer... stick with subq.
Questions about a specific nasal peptide? Drop them below 👇
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Why Some Peptides Work as Nasal Sprays (And Most Don't)
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