Peptide Comparison
Polymyxin BvsThymalin
Cyclic lipopeptide antibiotic from Paenibacillus polymyxa containing 10 amino acids with 6 diaminobutyric acid residues and a fatty acid tail — FDA-approved since 1964 as a last-resort treatment for multidrug-resistant Gram-negative infections including Pseudomonas aeruginosa, Acinetobacter baumannii, and carbapenem-resistant Enterobacteriaceae, targeting lipid A of bacterial lipopolysaccharide with rapid bactericidal membrane disruption
Russian thymic peptide complex that rejuvenates immune function and supports healthy aging
At a Glance
Quick
comparison
Dose Range
Polymyxin B
1.5–2.5 mg/kg
Thymalin
5–10 mg
Frequency
Polymyxin B
Multiple times daily
Thymalin
Once daily
Administration
Polymyxin B
Intravenous infusion (primary systemic route)
Thymalin
Intramuscular injection
Cycle Length
Polymyxin B
4-6 weeks
Thymalin
4-6 weeks
Onset Speed
Polymyxin B
Rapid (hours to days)
Thymalin
Moderate (1-2 weeks)
Evidence Level
Polymyxin B
Strong human trials (Phase 3 or FDA approved)
Thymalin
Limited human trials
Efficacy
Benefit
ratings
Fighting Resistant Infections
Stopping Bacterial Toxins
Wound Protection
Immune Restoration
Longevity Support
Disease Prevention
Technical Data
Compound
specifications
Polymyxin B
Molecular Formula
C₅₆H₉₈N₁₆O₁₃ (polymyxin B₁ free base)
Molecular Weight
1,203.5 g/mol (free base); ~1,385 g/mol (sulfate salt)
Half-Life
Terminal half-life: 9-11.5 hours in patients with normal renal function; does not require renal dose adjustment (unlike colistimethate); achieves steady-state within 1-2 days with loading dose
Bioavailability
IV: 100% (direct administration); oral: negligible (not absorbed from GI tract — used topically in the gut for selective decontamination); inhaled: local pulmonary concentrations achieved with systemic absorption variable; topical: minimal systemic absorption
CAS Number
1405-20-5 (polymyxin B sulfate)
Thymalin
Molecular Formula
Complex mixture; active dipeptide EW: C16H19N3O5
Molecular Weight
Polypeptide complex; components 250-1000 Da; active dipeptide EW ~321 Da
Half-Life
Not precisely characterized for complex; immune effects persist weeks post-administration
Bioavailability
High via intramuscular or subcutaneous injection
CAS Number
63958-90-7
Protocols
Dosing
tiers
Polymyxin B
Thymalin
Applications
Best
suited for
Polymyxin B
Treatment of life-threatening multidrug-resistant Gram-negative infections when carbapenems and other agents have failed
Polymyxin B is particularly well-suited for individuals focused on treatment of life-threatening multidrug-resistant gram-negative infections when carbapenems and other agents have failed. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Salvage therapy for carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infections and pneumonia
Polymyxin B is particularly well-suited for individuals focused on salvage therapy for carbapenem-resistant acinetobacter baumannii (crab) bloodstream infections and pneumonia. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Intrathecal/intraventricular treatment of MDR Gram-negative meningitis and ventriculitis
Polymyxin B is particularly well-suited for individuals focused on intrathecal/intraventricular treatment of mdr gram-negative meningitis and ventriculitis. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Inhaled therapy for MDR Gram-negative ventilator-associated pneumonia (VAP) as adjunct to systemic therapy
Polymyxin B is particularly well-suited for individuals focused on inhaled therapy for mdr gram-negative ventilator-associated pneumonia (vap) as adjunct to systemic therapy. Research and clinical experience suggest meaningful benefits in this area when used as part of a comprehensive treatment approach.
Thymalin
Aging Adults Seeking Immune Support
Thymalin is especially valuable for people over 55 whose thymus gland has naturally shrunk with age. By stimulating thymic function, it helps restore the immune training center that your body relies on to fight infections and stay healthy.
Longevity and Anti-Aging Protocols
Clinical studies tracking patients for 6-8 years showed Thymalin reduced mortality by 2.0-2.1-fold. Combined with Epitalon, the mortality reduction reached an impressive 4.1-fold, making this combination one of the most studied longevity peptide protocols.
Seasonal Illness Prevention
Research shows Thymalin cuts respiratory infection rates by 2.0-2.4-fold. A short 10-day course before cold and flu season can significantly boost your immune defenses for months afterward.
Safety Profile
Side
effects
Polymyxin B
Common
- Nephrotoxicity
- Infusion-related histamine release
- Neurotoxicity
- Skin hyperpigmentation
Uncommon
- Neuromuscular blockade
Serious
- Acute kidney injury requiring dialysis
Thymalin
Common
- No side effects in most patients
- Mild injection site reaction
Uncommon
- Transient low-grade fever
- Mild flu-like symptoms
- Temporary headache
Serious
- Severe allergic reaction
Research Status
Safety
& evidence
Polymyxin B
Evidence Level
Strong human trials (Phase 3 or FDA approved)
FDA Status
FDA approved for this use
Safety Overview
Polymyxin B carries significant nephrotoxicity risk (acute tubular necrosis) and neurotoxicity risk (peripheral neuropathy, neurological effects) requiring strict monitoring. Serum concentrations >5 mg/L associated with increased renal dysfunction; dosing adjusted for creatinine clearance to minimize accumulation. IV or intramuscular use only; intrathecal administration reserved for meningitis with careful dosing. Bacterial resistance monitoring essential as polymyxins remain reserved antibiotics.
Contraindications
- xKnown hypersensitivity to polymyxin B or polymyxin E (colistin)
- xSevere pre-existing renal failure without dialysis support — nephrotoxicity may be life-threatening
- xConcurrent use of other nephrotoxic agents (aminoglycosides, vancomycin, amphotericin B) without renal monitoring — additive nephrotoxicity risk
- xMyasthenia gravis — polymyxin B can exacerbate neuromuscular blockade and precipitate respiratory failure
Thymalin
Evidence Level
Limited human trials
FDA Status
Research compound
Safety Overview
Thymalin has an excellent safety profile based on over 40 years of clinical use in Russia. Most patients experience zero side effects, and the peptide complex has been described as 'practically non-toxic' in research literature. It has been used safely in thousands of patients, including elderly populations over extended periods.
Contraindications
- xActive thymic tumors or malignancies
- xKnown hypersensitivity to animal-derived peptide products
- xPregnancy and breastfeeding (insufficient safety data)
- xSevere uncontrolled autoimmune disease without medical supervision
Decision Guide
Which is
right for you?
Choose Polymyxin B if...
- Treatment of life-threatening multidrug-resistant Gram-negative infections when carbapenems and other agents have failed
- Salvage therapy for carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infections and pneumonia
- Intrathecal/intraventricular treatment of MDR Gram-negative meningitis and ventriculitis
- Inhaled therapy for MDR Gram-negative ventilator-associated pneumonia (VAP) as adjunct to systemic therapy
Choose Thymalin if...
- Immune system restoration in aging adults
- Longevity and healthy aging support
- Reducing infection frequency and severity
- Multi-system health optimization