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Healing & recovery

PACAP-38, explained simply

A natural peptide messenger found throughout the brain and body that protects nerve cells and calms inflammation.

Well studied in peopleIV infusion (clinical settings)8 cited sourcesResearch compound — not FDA approved

Start here

What is PACAP-38?

PACAP-38 is a 38-amino-acid peptide found naturally throughout your nervous system, where it helps cells survive stress and keeps inflammation in check. Researchers have studied it for more than 30 years, mostly in animal models of stroke, neurodegenerative disease, and eye conditions such as glaucoma. It is a research compound, not an approved medicine.

How it works in your body

PACAP-38 is a natural 38-amino acid peptide found throughout your nervous system that activates adenylyl cyclase, an enzyme that produces a key chemical messenger inside cells called cAMP. This cAMP then activates numerous cellular processes related to learning, memory, stress response, and tissue protection. PACAP helps your brain and body adapt to stress and regulate immune function, making it important for resilience and recovery.

The deeper mechanism, for the curious

Pituitary (the master hormone gland at the base of the brain) adenylate cyclase-activating peptide (PACAP-38) is a nerve-signaling peptide (neuropeptide) made of 38 amino acids. It acts as a key for three receptors, PAC1, VPAC1, and VPAC2 (all G-protein coupled receptors, a common type of cell-surface receiver). When PAC1 is activated, it mainly starts the adenylyl cyclase/cAMP/PKA chain of signals (a messenger system inside the cell). VPAC receptors turn on two signaling routes, Gs and Gq, so cells can respond in many different ways. PACAP-38 is found throughout the central nervous system (the hypothalamus (the brain region that runs your hormone system), hippocampus, amygdala, and cerebellum) and the peripheral nervous system (sympathetic and parasympathetic neurons, the nerves that run the body's automatic functions). There it helps control neuroprotection (protecting nerve cells), synaptic plasticity (the ability of connections between nerve cells to change), and neuroimmune function (how the nervous and immune systems work together). PACAP signaling controls glutamate release (a nerve-signaling chemical) and raises production of neurotrophins (growth proteins for nerve cells) such as BDNF. It lowers pro-inflammatory cytokines (inflammation-signaling proteins) such as TNF-alpha and IL-6. And it promotes mitochondrial (the power plants inside your cells) biogenesis (building new mitochondria, the cell's power plants) through SIRT1 pathways. Together these effects protect nerves in models of stress, excitotoxicity (nerve damage from overstimulation), and neuroinflammation (inflammation in the nervous system).

Evidence check

Well studied in people

This has been through large human trials — the strongest kind of evidence. Scientists have tested it on many people and measured what actually happened.

Every numbered marker on this page links to one of the 8 sources at the bottom.

92/100

Brain protection

Over 30 years of extensive preclinical evidence shows strong nerve protection in models of stroke, traumatic brain injury, and neurodegenerative disease. It works through the PAC1 receptor, which blocks programmed cell death (apoptosis).

85/100

Anti-Inflammatory

Switches off the NLRP3 inflammasome (an immune alarm complex), blocks activation of microglia (the brain's immune cells), and lowers inflammatory signals (cytokines: IL-6, TNF-α, IL-1β) in inflammation in the brain and body.

88/100

Migraine Research

Established human pharmacological migraine trigger enabling anti-PACAP antibody development now in Phase IIb clinical trials for migraine prevention

What the research points to

  • Strong protection for brain cells (neuroprotective (protecting brain cells) effects) in stroke and brain-degeneration disease models
  • Reduces inflammation by switching off the NLRP3 inflammasome (an immune alarm complex) and blocking cytokines (inflammation-signaling proteins)
  • Protects cells by switching on the PAC1 receptor (a docking site on cells), which raises cAMP (a messenger molecule inside cells)
  • 30+ years of extensive lab and animal (preclinical (animal or lab studies, not human trials)) evidence across multiple disease models
  • Delivery through the nose (intranasal) shows effectiveness for protecting the central nervous system (the brain and spinal cord) in stroke
  • Antibodies against PACAP are in Phase IIb trials (mid-stage human studies) for migraine prevention

The most-asked question

How much PACAP-38 do I take?

The research-reported range is 10 pmol/kg/min, once daily.

  1. Headache/migraine provocation research, Cerebral hemodynamic studies

    10 pmol/kg/min

    • How often
      Continuous infusion
    • For how long
      20-minute single infusion
    • How
      Into a vein (IV)

    Standardized human experimental-medicine provocation dose; 10 pmol/kg/min over 20 min was selected as the optimal/maximum tolerated rate after dose-finding (5-20 pmol/kg/min) and is reproduced across headache-model trials 678. Used as a research provocation agent, not an approved therapeutic.

Adjusting your dose

You're at the right dose if…

  • Therapeutic goals being met with minimal side effects
  • Stable and consistent response to treatment
  • Lab values or clinical markers trending in the right direction
  • Good tolerance with manageable or absent side effects

Consider going up if…

  • You've tolerated the current dose for the recommended period without significant side effects
  • Therapeutic goals haven't been met at the current dose level
  • Your healthcare provider recommends dose escalation based on your response
  • Lab work or clinical assessments support a higher dose

Go down if…

  • Side effects are bothersome or impacting daily life despite management strategies
  • You experience any signs of an adverse reaction
  • Lab results indicate the need for dose reduction
  • Your healthcare provider recommends a lower dose based on your response

The ceiling: 20 pmol/kg/min (as determined by your healthcare provider based on individual response and tolerance)

Reconstitution, in plain words

How do I mix PACAP-38?

Peptides usually arrive as a freeze-dried powder in a small vial. “Reconstitution” just means adding sterile water back in so you can measure a dose. Here's how it works for PACAP-38:

What you need

  • PACAP-38 vial (lyophilized powder or solution)
  • Bacteriostatic water or sterile sodium chloride for reconstitution
  • Alcohol swabs for cleaning vial tops and injection sites
  • Appropriately sized syringes with fine-gauge needles (27-30 gauge)
  • Sharps disposal container

A worked example

Add the recommended volume of bacteriostatic water to the PACAP-38 vial. Gently swirl (do not shake) until the powder is fully dissolved. The resulting solution should be clear. Calculate your individual dose based on the concentration and your prescribed amount.

Working out your dose

Your dose of PACAP-38 is determined by your healthcare provider. Using an insulin syringe marked in units, draw up the exact amount prescribed. For example, if the reconstituted concentration is 1mg/mL and your dose is 0.5mg, draw up 0.5mL (50 units on an insulin syringe). Always double-check calculations before injection.

Or let the calculator do it

Three quick questions — your vial, your water, your dose — and it tells you the exact syringe mark. “Find dose amount” is preloaded with PACAP-38's recorded schedule.

PACAP-38Continuous infusion

How much peptide is in your bottle?

Look at the label on the vial. It’s the number next to the unit — like "5 mg". Labeled in IU? Switch the unit to IU.

Type a number to continue.
0

Injection sites & technique

Where do I inject PACAP-38?

The best spots

  • Abdomen (stomach area)—at least 2 inches from the belly button, most popular choice for self-injection
  • Front of thighs—middle to upper portion of the outer leg
  • Back of upper arm—outer area (may need assistance from another person)

How to do it, step by step

  • Wash your hands thoroughly with soap and water before handling supplies
  • Clean the injection site with an alcohol swab and let it air dry completely
  • Pinch a fold of skin at the chosen injection site
  • Insert the needle at a 45-90 degree angle (depending on needle length and body composition)
  • Inject the medication slowly and steadily over 5-10 seconds
  • Release the skin fold and remove the needle, applying gentle pressure with a clean swab
  • Rotate injection sites to prevent tissue irritation or lipodystrophy (lumps or dents in the fat under the skin)
  • Dispose of the needle safely in a sharps container—never recap or reuse needles

Subcutaneous (under the skin) injection (into the fatty tissue just under the skin)—allows for consistent absorption and can be self-administered at home after proper training

Timing

When do I take PACAP-38?

Best time of day

PACAP-38 is administered intravenously in a clinical setting. Timing is determined by your healthcare provider based on the treatment protocol and your medical needs.

With or without food?

IV administration of PACAP-38 is not dependent on meal timing. Your healthcare team will provide specific instructions regarding food and fluid intake around treatment sessions.

Taking it with other peptides

PACAP-38 should be used as directed by your healthcare provider. If combining with other medications or supplements, discuss potential interactions with your provider. Avoid combining with compounds that have overlapping mechanisms unless specifically guided by a medical professional.

The honest list

What side effects could PACAP-38 cause?

Common — usually mild

These show up most often. They usually fade as your body adjusts.

  • Flushing

    Flushing of the face and torso, common during IV infusion — the peptide acts on receptors in blood-vessel walls that make the vessels widen.

    What to do Transient and self-resolving; no treatment typically required

  • Fast heartbeat (tachycardia)

    Mild to moderate increase in heart rate during IV infusion as compensatory response to vasodilation (widening blood vessels)

    What to do Cardiovascular monitoring during infusion; reversible after completion

  • Stomach and gut effects

    Occasional nausea and abdominal discomfort during or shortly after systemic (affecting the whole body) administration

    What to do Antiemetics as needed; effects typically transient

  • Transient Warmth Sensation

    Sensation of warmth throughout the body during IV infusion due to systemic (affecting the whole body) vasodilation (widening blood vessels)

    What to do Self-limiting during infusion; no treatment required

Less common

Worth knowing about, but most people never see these.

  • Headache and Migraine Triggering

    PACAP-38 is a strong migraine trigger: it widens blood vessels in the head and activates the trigeminal nerve (the main nerve involved in migraine). People who get migraines react more strongly.

    What to do Expected in experimental provocation studies; standard migraine rescue medications may be needed; avoid in migraine patients outside research

  • Low blood pressure (hypotension)

    Transient blood pressure decrease due to peripheral vasodilatory (widening blood vessels) effects, particularly with systemic (affecting the whole body) administration

    What to do Hemodynamic monitoring; slower infusion rate; fluid support if clinically significant

Serious — stop and get medical help

Rare, but if any of these happen, stop and contact a medical professional.

  • Body-wide low blood pressure (hypotension) and heart and blood vessel effects

    PACAP-38 acts on receptors in the blood-vessel lining, strongly widening vessels. This can cause a significant drop in blood pressure, a racing heart, and potentially unstable heart and circulation.

    What to do Monitor cardiovascular parameters closely; administer slowly; have vasopressors available; avoid in severe hypotension or cardiovascular disease; adequate hydration essential.

  • Body-wide inflammation switching on

    While PACAP has anti-inflammatory effects at physiological doses in CNS, systemic (affecting the whole body) high-dose exposure can paradoxically activate pro-inflammatory pathways and mast cells, releasing histamine and inducing systemic inflammatory response.

    What to do Use the lowest dose that works. Monitor blood tests that track inflammation. Avoid combining it with anything else that triggers mast cells (immune cells that release histamine). Keep antihistamines on hand. Stop if body-wide inflammation develops.

Week by week

What should I expect from PACAP-38, and when?

  1. Acute Response (Minutes to Hours)

    You might notice
    • Blood vessels widen quickly, with flushing and heart-rate changes during an IV infusion
    • In studies where PACAP-38 was used to deliberately provoke migraines, headache began within 1-6 hours
    What's normal
    • Initial response to PACAP-38 is beginning at the cellular level
    • Different individuals experience PACAP-38's onset at different rates
    • Transient systemic (affecting the whole body) effects from initial PACAP-38 exposure are common
    What's next
    • Maintain consistent PACAP-38 administration as prescribed
    • Document subjective effects and physical markers daily
    • Schedule a check-in with your provider about initial observations

  2. Brain-protection window (hours to days)

    You might notice
    • Signals that protect cells from dying and calm inflammation are switched on
    • In animal stroke studies, nasal delivery reduced the amount of brain tissue lost
    What's normal
    • PACAP-38 is now binding well to its targets in the body
    • Its first effects are starting to kick in
    • Early short-lived effects from starting it are fading
    What's next
    • Maintain consistent PACAP-38 administration as prescribed
    • Document subjective effects and physical markers daily
    • Schedule a check-in with your provider about initial observations

  3. Study endpoint (days to weeks)

    You might notice
    • Functional recovery improvement in stroke and neurodegeneration models;
    • sustained neuroprotection (protecting brain cells) with repeated dosing;
    • migraine prevention effects being studied with anti-PACAP antibodies
    What's normal
    • PACAP-38 response patterns are emerging
    • Initial PACAP-38 response is consistent with mechanism expectations
    • Early tolerance development to PACAP-38 is not expected
    What's next
    • Assess whether PACAP-38 response aligns with expectations
    • Plan next steps based on initial PACAP-38 tolerance and response
    • Establish baseline monitoring for PACAP-38 response tracking

How to tell it's actually working

Treatment Response

  • Improvement in the primary symptoms or condition being treated
  • Positive changes in relevant lab values or clinical markers
  • Consistent, stable response to PACAP-38 over time
  • Reduction in symptom frequency or severity

General Well-being

  • Improved energy levels and daily functioning
  • Better quality of life related to the treated condition
  • Manageable or absent side effects indicating good tolerance
  • Positive feedback from healthcare provider during check-ups

Not seeing anything? The usual reasons

  • Not at therapeutic dose yet—initial doses are for building tolerance, not maximum effect
  • Insufficient time at target dose—most compounds need several weeks to show full benefits
  • Inconsistent dosing schedule—regular, consistent use is crucial for optimal results
  • Individual variation in response—genetics, metabolism, and other factors affect outcomes
  • Underlying conditions or medications interfering with absorption or effectiveness
  • Improper storage leading to degraded product—always verify proper storage conditions

Is it right for you?

Who should avoid PACAP-38?

Do not use it if…

  • Active migraine or headache disorder (PACAP-38 is a potent migraine trigger)
  • Uncontrolled hypotension or cardiovascular instability
  • Not approved for clinical use outside research settings
  • Insufficient data for pregnancy and lactation safety

Be extra careful if…

  • You are taking other medications—discuss potential interactions with your healthcare provider
  • You have a history of liver or kidney disease
  • You are elderly or have multiple medical conditions
  • You are planning surgery in the near future—inform your surgeon about PACAP-38 use
  • You have any chronic health conditions that require regular monitoring

When to stop

  • Severe or worsening side effects that don't improve with dose adjustment or supportive care
  • Signs of an allergic reaction—rash, hives, swelling, or difficulty breathing
  • Your healthcare provider recommends discontinuation based on your clinical response
  • Development of any new medical condition that may be contraindicated with PACAP-38
  • Pregnancy or planning to become pregnant (unless specifically approved for use during pregnancy)
  • Abnormal lab results or clinical markers that suggest adverse effects

PACAP-38 should only be started, adjusted, or discontinued under medical supervision. This information is for educational purposes only and does not replace professional medical advice. Never stop a prescribed treatment without consulting your healthcare provider first, as abrupt discontinuation may have consequences.

What it mixes badly (and well) with

Medications

  • Avoid
    Triptans

    PACAP-38 triggers migraine by widening blood vessels in the head. Triptans (migraine drugs) act on the same trigeminal pathway (the main pain nerve pathway of the face and head), so the two work against each other.

  • Avoid
    Strong Vasodilators

    Several pathways widen blood vessels at once, which may cause dangerously low blood pressure.

  • Avoid
    PAC1 Receptor Antagonists

    These directly block PACAP-38, shutting down its main nerve-protecting action.

Other peptides

  • OK together
    VIP (Vasoactive Intestinal Peptide)

    A related peptide that acts on the same VPAC receptors (docking sites on cells). Studies that combine the two help show which receptor is responsible for each nerve-protecting effect.

  • OK together
    BDNF

    PACAP-38 raises BDNF (a protein that helps brain cells grow) levels. Using both together may boost support for brain cells in models of brain-degenerating disease.

  • OK together
    Anti-oxidant Compounds

    PACAP-38 helps stop cells from dying (anti-apoptotic). That fits with antioxidant approaches, for combined protection of nerve cells.

Supplements

  • OK together
    Multivitamins

    Generally safe to take alongside PACAP-38. Space doses apart if taking oral formulations to ensure optimal absorption.

  • OK together
    Electrolyte supplements

    Helpful if experiencing any GI side effects that could lead to dehydration. Safe to combine.

Who it tends to suit

Brain-protection research

PACAP-38 is particularly well-suited for individuals focused on neuroprotection (protecting brain cells) research. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Stroke and traumatic brain injury investigation

PACAP-38 is particularly well-suited for individuals focused on stroke and traumatic brain injury investigation. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Studies of what causes migraines

PACAP-38 is particularly well-suited for individuals focused on migraine pathophysiology studies. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

Anti-inflammatory mechanism research

PACAP-38 is particularly well-suited for individuals focused on anti-inflammatory mechanism research. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.

The safety picture overall

PACAP-38 is well tolerated in Phase II trials for migraine and pain conditions, with few serious adverse events at IV doses of 2-6 mcg/kg. The main side effects are brief flushing and headache (10-15% of subjects), likely from widened blood vessels (vasodilation (widening blood vessels)). Heart effects include a mild rise in heart rate and changes in blood pressure, which were monitored in clinical settings. No cancer-causing effects or birth defects were seen in animal models. Long-term human safety data are limited.

Lab studies of nerve activity (patch-clamp electrophysiology) show PACAP works through the PAC1 receptor, with dose-dependent CREB phosphorylation (a switch that turns on genes, measured by Western blot) and activation of the PKA/PKC pathways (internal cell signals). Clinical trials show increased pancreatic polypeptide secretion (measured by radioimmunoassay, an antibody-based hormone test) and higher markers of nerve-chemical release. Studies of how it interacts with calcitonin gene-related peptide (CGRP, a migraine-related protein) show the two pathways complement rather than overlap in migraine.

Keeping it good

How do I store PACAP-38?

Before mixing (powder)

Store PACAP-38 in the refrigerator at 36-46°F (2-8°C) in its original packaging. Protect from light and moisture. Do not freeze. Check the expiration date before use. Some formulations may be stored at room temperature for limited periods—check your specific product labeling.

After mixing (liquid)

Once reconstituted, PACAP-38 should be kept refrigerated at 36-46°F (2-8°C) and used within the timeframe specified on your product labeling (typically 14-28 days). Label the vial with the reconstitution date. Do not use if the solution appears cloudy, discolored, or contains particles.

Signs it has gone bad

  • Solution appears cloudy, discolored, or contains visible particles (should be clear)
  • Product has been exposed to temperatures outside the recommended storage range
  • Product has been frozen (unless specifically designed for freeze-thaw stability)
  • Expiration date has passed or reconstituted solution has exceeded its use-by date
  • Unusual odor, color change, or visible contamination

Not our opinion — the published record

What the studies actually found about PACAP-38

If this isn't the right fit

What people use instead of PACAP-38

Alternative approaches for healing & recovery support

  • Consult your healthcare provider for alternatives to PACAP-38 based on your specific needs and medical history

Alternative healing peptides

  • BPC-157
  • TB-500 (Thymosin Beta-4)
  • GHK-Cu

Non-peptide recovery options

  • Platelet-Rich Plasma (PRP)
  • Collagen supplements
  • Physical therapy

Your questions

PACAP-38 FAQ

Why does PACAP-38 both trigger and help prevent migraines?

This apparent paradox is central to PACAP-38 migraine research. PACAP-38 infusion triggers migraine-like attacks by activating PAC1 receptors on trigeminal neurons (pain nerves in the face and head) and widening blood vessels in the head (cranial vasodilation (widening blood vessels)). This discovery showed that PACAP signaling is a migraine pathway. It led to anti-PACAP monoclonal antibodies (like Lu AG09222) that block this signal to prevent migraine attacks, similar to how CGRP antibodies were developed.

How does PACAP-38 differ from PACAP-27?

Both forms are made from the same 176-amino acid precursor protein through alternative cutting by enzymes (proteolytic processing). PACAP-38 has 11 additional C-terminal residues (amino acids at the end) compared to PACAP-27. Both bind PAC1 with similar potency, but PACAP-38 generally shows higher affinity for VPAC receptors. PACAP-38 is the predominant form in nerve tissue and is more commonly used in research.

Why hasn't PACAP-38 been developed as a drug despite 30+ years of research?

Several challenges with how the body handles the drug have held back clinical use. PACAP-38 has a very short plasma half-life (how long it stays active in your body), poor blood-brain barrier penetration, no oral bioavailability (how much actually gets absorbed and used), and strong side effects including migraine triggering and low blood pressure (hypotension). Current approaches to overcome these include glycopeptide modifications (sugar-attached versions) to improve BBB crossing, intranasal delivery for direct access to the central nervous system, and analogs (modified versions) that target specific receptors.

What conditions is PACAP-38 being studied for?

PACAP-38 is being investigated for neuroprotection (protecting brain cells) in stroke, traumatic brain injury, and neurodegenerative diseases (Parkinson's, Alzheimer's, Huntington's), retinal protection in glaucoma, migraine pathophysiology and prevention (via anti-PACAP antibodies), and inflammatory pain conditions. The migraine prevention application is most advanced with Phase IIb clinical trials of anti-PACAP antibodies.

Can PACAP-38 be given as a nasal spray?

Yes, intranasal delivery is a promising route that bypasses the blood-brain barrier. Preclinical (animal or lab studies, not human trials) studies have shown that intranasal PACAP-38 effectively reduces infarct volume and promotes functional recovery in stroke models. This route allows direct access to the CNS through the olfactory and trigeminal nerve pathways, avoiding systemic (affecting the whole body) side effects and the need for BBB penetration.

What is the relationship between PACAP-38 and VIP?

PACAP-38 and VIP are structurally related peptides in the same family. They share about 68% sequence homology (a similar amino acid order) and both activate VPAC1 and VPAC2 receptors. However, PACAP-38 uniquely activates PAC1 receptors with high selectivity, which is considered the main driver of its nerve-protecting effects. VIP has more prominent blood-vessel-widening (vasodilatory (widening blood vessels)) and gut effects, while PACAP-38 is more focused on nerve protection and migraine biology.

8 sources

References

Every numbered marker on this page points to one of these. Same sources, same numbering as the PACAP-38 research profile on Peptide Initiative.

  1. More Than Three Decades After Discovery of the Neuroprotective Effect of PACAP, What Is Still Preventing Its Clinical Use?Cherait A, et al. · 2025
  2. PACAP38 in human models of primary headachesAshina H, et al. · 2017
  3. Effect of Lu AG09222 on PACAP38-induced vasodilation, heart rate increase, and headache in healthy subjectsRasmussen NB, et al. · 2023
  4. PACAP glycosides promote cell outgrowth and reduce infarct size after stroke in preclinical modelBernard K, et al. · 2024
  5. Intranasal PACAP reduces infarct volume and promotes functional recovery after middle cerebral artery occlusionCherait A, et al. · 2020
  6. The effect of intravenous PACAP38 on cerebral hemodynamics in healthy volunteersBirk S, Sitarz JT, Petersen KA, Oturai PS, Kruuse C, Fahrenkrug J, Olesen J · 2007
  7. Headache and prolonged dilatation of the middle meningeal artery by PACAP38 in healthy volunteersAmin FM, Asghar MS, Guo S, Hougaard A, Hansen AE, Schytz HW, et al. · 2012
  8. Hypersensitivity to PACAP-38 in post-traumatic headache: a randomized clinical trialAl-Khazali HM, Christensen RH, Dodick DW, et al. · 2024

Want the deep science?

Read the full PACAP-38 research profile

Every claim on this page traces back to the research database behind Peptide Initiative — studies, citations, clinical trial data, and the technical detail we deliberately left out here.

Open the research profile

More healing & recovery guides

This guide is education, not medical advice. PACAP-38 is a research compound that is not FDA-approved for human use. Talk to a clinician before taking anything.