Peptide profile · Healing & Recovery
PACAP-38
Neuroprotective polypeptide with potent anti-inflammatory and cytoprotective properties discovered in 1989
Written & reviewed by Michael Carroll · Research, Peptide Initiative
Typical dose
10 pmol/kg/min
Half-life
Very short plasma half-life (minutes); rapid enzymatic degradation
Bioavailability
IV: systemic; Intranasal: direct CNS access bypassing BBB; poor oral bioavailability
Molecular weight
~4534 Da
Evidence level
Strong human trials
01 · Compound profile
Scientific & efficacy data
Molecular formula
C203H331N63O53S
Primary benefits
Over 30 years of extensive preclinical evidence demonstrating potent neuroprotection in stroke, TBI, and neurodegenerative disease models through PAC1 receptor-mediated anti-apoptotic signaling
Suppresses NLRP3 inflammasome, inhibits microglial activation, and reduces pro-inflammatory cytokines (IL-6, TNF-α, IL-1β) in central and peripheral inflammation
Established human pharmacological migraine trigger enabling anti-PACAP antibody development now in Phase IIb clinical trials for migraine prevention
Tulane University School of Medicine
Amino acid sequence
HSDGIFTDSYSRYRKQMAVKKYLAAVLGKRYKQRVKNK (38 amino acids)02 · Dosing
How much do I take?
10 pmol/kg/min · continuous infusion
Intravenous: Delivered straight into a vein through a drip (IV), done by a clinician.
Bioavailability Complete (about 100%) — delivered straight into the bloodstream.
Best time to take
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 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.
If stacking
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.
＋ Increase 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
－ Decrease 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
✓ Signs of right dose
- ✓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
Dosing Calculator
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03 · Suitability
Is this right for me?
Best for neuroprotection research & stroke and traumatic brain injury investigation
Best for
Neuroprotection research
PACAP-38 is particularly well-suited for individuals focused on neuroprotection 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.
Migraine pathophysiology studies
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.
Consider alternatives if
Do not use if
Use with caution if
Not sure?
Compare PACAP-38 with similar peptides to find the best fit for your goals.
04 · Administration
How do I use it?
Intravenous infusion · Intranasal
Reconstitution — what you need
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.
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.
Route
Subcutaneous injection (into the fatty tissue just under the skin)—allows for consistent absorption and can be self-administered at home after proper training
Best sites
Technique
- 01Wash your hands thoroughly with soap and water before handling supplies
- 02Clean the injection site with an alcohol swab and let it air dry completely
- 03Pinch a fold of skin at the chosen injection site
- 04Insert the needle at a 45-90 degree angle (depending on needle length and body composition)
- 05Inject the medication slowly and steadily over 5-10 seconds
- 06Release the skin fold and remove the needle, applying gentle pressure with a clean swab
- 07Rotate injection sites to prevent tissue irritation or lipodystrophy
- 08Dispose of the needle safely in a sharps container—never recap or reuse needles
Storage · before reconstitution
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.
Storage · after reconstitution
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 of degradation
Sample daily schedule
05 · Safety
Is it safe?
4 common side effects · 2 serious
PACAP-38 shows good tolerability in Phase II trials for migraine and pain conditions with minimal serious adverse events at IV doses of 2-6 mcg/kg. Primary side effects are transient flushing and headache (10-15% of subjects), likely related to vasodilation. Cardiovascular effects include mild heart rate increase and blood pressure changes, monitored in clinical settings. No carcinogenicity or teratogenicity in animal models; limited long-term safety data in humans.
Preclinical neurophysiology using patch-clamp electrophysiology demonstrates PACAP's PAC1 receptor mechanism with dose-dependent CREB phosphorylation (Western blot) and PKA/PKC activation pathways. Clinical trials show increased pancreatic polypeptide secretion (measured via radioimmunoassay) and neuropeptide release markers. Migraine mechanism confirmed through calcitonin gene-related peptide (CGRP) interaction studies showing complementary rather than overlapping pathways.
Common side effects · experienced by some users
Less common
These typically resolve with continued use or dose adjustment.
Stop and seek help if
- ×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.
With other peptides
- ✓VIP (Vasoactive Intestinal Peptide) — Related peptide sharing VPAC receptor targets; combination studies elucidate receptor-specific contributions to neuroprotection
- ✓BDNF — PACAP-38 upregulates BDNF expression; co-administration may enhance neurotrophic support in neurodegeneration models
- ✓Anti-oxidant Compounds — PACAP-38 anti-apoptotic effects complement antioxidant strategies for synergistic neuroprotection
With medications
- !Triptans — PACAP-38 triggers migraine through cranial vasodilation; triptans target the same trigeminal pathway creating pharmacological conflict
- !Strong Vasodilators — Additive vasodilation through multiple pathways may cause dangerous hypotension
- !PAC1 Receptor Antagonists — Direct pharmacological antagonism blocks PACAP-38 primary neuroprotective mechanism
With supplements
- ✓Multivitamins — Generally safe to take alongside PACAP-38. Space doses apart if taking oral formulations to ensure optimal absorption.
- ✓Electrolyte supplements — Helpful if experiencing any GI side effects that could lead to dehydration. Safe to combine.
06 · Effectiveness
How do I know it's working?
Strong human trials · first signs acute response (minutes to hours)
Evidence level
Strong human trials
(Phase 3 or FDA approved)
How it works
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.
Pituitary adenylate cyclase-activating peptide (PACAP-38) is a 38-amino acid neuropeptide that acts as a ligand for PAC1, VPAC1, and VPAC2 G-protein coupled receptors. PAC1 receptor activation preferentially triggers adenylyl cyclase/cAMP/PKA signaling, while VPAC receptor activation activates both Gs and Gq pathways, enabling diverse cellular responses. PACAP-38 is widely distributed in the CNS (hypothalamus, hippocampus, amygdala, cerebellum) and PNS (sympathetic and parasympathetic neurons), where it regulates neuroprotection, synaptic plasticity, and neuroimmune function. PACAP signaling modulates glutamate release, enhances neurotrophin expression (BDNF), suppresses pro-inflammatory cytokines (TNF-alpha, IL-6), and promotes mitochondrial biogenesis through SIRT1 pathways, making it neuroprotective in stress, excitotoxicity, and neuroinflammation models.
What to expect
Acute Response (Minutes to Hours)
What you might notice
- •Rapid onset vasodilation, flushing, and heart rate changes during IV infusion;
- •headache onset within 1-6 hours in migraine provocation studies
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 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
Neuroprotective Window (Hours to Days)
What you might notice
- •Anti-apoptotic and anti-inflammatory signaling activated;
- •infarct volume reduction observed with intranasal delivery in stroke models
What's normal
- •PACAP-38 is achieving sufficient receptor engagement
- •Initial mechanism of PACAP-38 is taking effect
- •Early transient effects from PACAP-38 administration are resolving
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
Research Endpoint (Days to Weeks)
What you might notice
- •Functional recovery improvement in stroke and neurodegeneration models;
- •sustained neuroprotection 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
Signs it's 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
Signs it's working · 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 results? Common 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
Key research
07 · Questions
Frequently asked
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 and causing cranial vasodilation. This discovery validated PACAP signaling as a migraine pathway, leading to development of anti-PACAP monoclonal antibodies (like Lu AG09222) that block this signaling to prevent migraine attacks, similar to how CGRP antibodies were developed.
How does PACAP-38 differ from PACAP-27?+
Both forms are derived from the same 176-amino acid precursor protein through alternative proteolytic processing. PACAP-38 has 11 additional C-terminal residues 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 neural tissues and is more commonly used in research.
Why hasn't PACAP-38 been developed as a drug despite 30+ years of research?+
Several pharmacokinetic challenges have hindered clinical translation: PACAP-38 has a very short plasma half-life, poor blood-brain barrier penetration, no oral bioavailability, and potent side effects including migraine triggering and hypotension. Current approaches to overcome these include glycopeptide modifications to improve BBB crossing, intranasal delivery for direct CNS access, and development of receptor-selective analogs.
What conditions is PACAP-38 being studied for?+
PACAP-38 is being investigated for neuroprotection 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 delivered intranasally?+
Yes, intranasal delivery is a promising route that bypasses the blood-brain barrier. Preclinical 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 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 superfamily. They share approximately 68% sequence homology and both activate VPAC1 and VPAC2 receptors. However, PACAP-38 uniquely activates PAC1 receptors with high selectivity, which is considered the primary mediator of its neuroprotective effects. VIP has more prominent vasodilatory and GI effects, while PACAP-38 is more focused on neuroprotection and migraine pathophysiology.
08 · Further reading
History & related research
History · since 1989
The brain's emergency repair signal discovered in 1989
A 38-amino acid peptide that acts like your brain's bodyguard, protecting nerve cells from death and damage. Found in 1989, PACAP-38 is being researched to help stroke patients and people with brain injuries heal faster.
Read the full history of PACAP-38