Thymosin Beta-4 vs VIP (Vasoactive Intestinal Peptide)
The body's natural healing peptide that accelerates tissue repair and reduces inflammation
Endogenous neuropeptide with vasodilatory, anti-inflammatory, and immunomodulatory properties
Written by Michael Carroll — Owner, Director of Research · Reviewed by the Peptide Initiative Research Team · Editorial standards
Quick comparison
Dose range
Thymosin Beta-4
2–5 mg
VIP (Vasoactive Intestinal Peptide)
50–50 mcg
Frequency
Thymosin Beta-4
Twice weekly
VIP (Vasoactive Intestinal Peptide)
Once daily
Administration
Thymosin Beta-4
Subcutaneous injection
VIP (Vasoactive Intestinal Peptide)
Intravenous infusion
Cycle length
Thymosin Beta-4
8-12 weeks
VIP (Vasoactive Intestinal Peptide)
Ongoing/indefinite
Onset speed
Thymosin Beta-4
Moderate (1-2 weeks)
VIP (Vasoactive Intestinal Peptide)
Moderate (1-2 weeks)
Evidence level
Thymosin Beta-4
Moderate human trials (Phase 1-2)
VIP (Vasoactive Intestinal Peptide)
Moderate human trials (Phase 1-2)
Benefit ratings
Wound Healing
Inflammation Reduction
Tissue Regeneration
Cardiovascular
Anti-Inflammatory
Neuroprotection
Compound specifications
Thymosin Beta-4
Molecular formula
C212H350N56O78S
Molecular weight
4963
Half-life
Dose-dependent (increases with higher doses)
Bioavailability
100% (subcutaneous and intravenous)
CAS number
77591-33-4
VIP (Vasoactive Intestinal Peptide)
Molecular formula
C147H237N43O43S
Molecular weight
3325.83 Da
Half-life
Approximately 1-2 minutes in plasma (rapid enzymatic degradation)
Bioavailability
IV: 100%; Inhaled: local pulmonary delivery; short systemic half-life
CAS number
37221-79-7
Dosing compared
Thymosin Beta-4
Subcutaneous injection
2-5 mg (community injectable practice for 'TB-500')
Once or twice weekly · 4-6 week loading phase, then weekly maintenance
Documented community/research-practice injectable dosing for tissue repair; thymosin beta-4 has ~100% bioavailability by the subcutaneous route [1]. Not an FDA-approved use.
Topical ophthalmic (eye drops)
0.1% (1 mg/mL) RGN-259 solution, 1 drop
Several times daily (e.g. up to 5x/day) · 4 weeks
0.1% RGN-259 ophthalmic solution used in phase III neurotrophic keratopathy and dry-eye trials, applied as eye drops several times daily for ~4 weeks [5].
Intravenous injection
450-1200 mg
IV push daily for the first 3 days, then weekly · Total of 7 doses over ~5 weeks
Doses studied in the RGN-352 acute myocardial infarction clinical program, given IV after PCI [6].
VIP (Vasoactive Intestinal Peptide)
Subcutaneous injection
50 mcg
Twice daily (morning and evening) · Ongoing per protocol
Common research/community practice dose for systemic/peripheral effects (approx., not from a controlled trial).
Inhaled
50 mcg per inhalation (200 mcg/day); 100 mcg single acute dose
Four inhalations daily · 12 weeks (chronic study)
Inhaled aviptadil in primary pulmonary hypertension: 4 inhalations/day; single 100 mcg dose used for acute vasoreactivity testing [7].
Intravenous infusion
50 → 100 → 150 pmol/kg/hr (ascending over 3 days)
12-hour infusion daily · 3 consecutive days
Aviptadil (ZYESAMI) dose-escalation regimen in critical COVID-19 respiratory failure trials [6]. Hospital/investigational only.
Best suited for
Thymosin Beta-4
Post-Surgery Recovery
Accelerates healing of surgical wounds and reduces post-operative inflammation and scarring
Chronic Wound Management
Helps pressure ulcers, venous stasis ulcers, and other slow-healing wounds progress faster
Tissue Regeneration
Supports repair of damaged tissues from injury, burns, or degenerative conditions
VIP (Vasoactive Intestinal Peptide)
Pulmonary arterial hypertension research
VIP (Vasoactive Intestinal Peptide) is particularly well-suited for individuals focused on pulmonary arterial hypertension research. [2][19] Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
ARDS and respiratory failure investigation
VIP (Vasoactive Intestinal Peptide) is particularly well-suited for individuals focused on ards and respiratory failure investigation. [1] Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Anti-inflammatory therapy development
VIP (Vasoactive Intestinal Peptide) is particularly well-suited for individuals focused on anti-inflammatory therapy development. [13][18] Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Neuroprotection studies
VIP (Vasoactive Intestinal Peptide) is particularly well-suited for individuals focused on neuroprotection studies. [15][16] Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Side effects
Thymosin Beta-4
Common
- Injection site redness
- Injection site swelling
Uncommon
- Temporary mild headache
- Mild bruising at injection site
- Transient fatigue
Serious
- Allergic reaction
VIP (Vasoactive Intestinal Peptide)
Common
- Facial Flushing
- Diarrhea
- Nausea
Uncommon
- Hypotension
- Tachycardia
- Cardiovascular Effects
Serious
- Hypotension
- Severe Flushing and Facial Erythema
Safety & evidence
Thymosin Beta-4
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
Thymosin Beta-4 is a naturally occurring peptide found in all cells and body fluids in the human body. Clinical trials have demonstrated excellent safety even at very high doses. IV studies showed doses up to 1260 mg were well tolerated with no serious adverse events.
Contraindications
- Active systemic infections
- Severe immunosuppression
- Hypersensitivity to thymosin or any component
- Pregnancy (insufficient safety data)
VIP (Vasoactive Intestinal Peptide)
Evidence level
Moderate human trials (Phase 1-2)
FDA status
Research compound
Safety overview
VIP (Vasoactive Intestinal Peptide) is a 28-amino acid endogenous neuropeptide [8] with moderate evidence from Phase 1-2 human clinical trials. The synthetic pharmaceutical form (aviptadil/RLF-100) received FDA fast-track designation for COVID-19-associated ARDS, [24] indicating recognition of its therapeutic potential. Critical safety considerations: VIP is a potent vasodilator that causes dose-dependent hypotension and compensatory tachycardia [6][10][11]—hemodynamic monitoring is essential during IV administration. Common side effects include facial flushing and diarrhea from its GI effects. [6] Phase 2b/3 COVID-19 ARDS trials (196 patients) reported NO serious drug-related adverse events, [1] a favorable safety signal. However, individual responses to vasodilation vary significantly based on baseline cardiovascular status, medications, and underlying conditions. The peptide's short plasma half-life (1-2 minutes) limits systemic accumulation. [10] Inhaled VIP shows excellent local tolerability for pulmonary applications with minimal systemic absorption [18][19].
Contraindications
- Uncontrolled hypotension or hemodynamic instability
- Severe cardiac decompensation
- Not approved for clinical use outside of trials
- Insufficient data for pregnancy and lactation safety
Which is right for you?
Choose Thymosin Beta-4 if...
- Recovering from injuries or surgery
- Improving wound healing speed
- Reducing inflammation
- Minimizing scar formation
Choose VIP (Vasoactive Intestinal Peptide) if...
- Pulmonary arterial hypertension research
- ARDS and respiratory failure investigation
- Anti-inflammatory therapy development
- Neuroprotection studies