Side-by-Side Comparison · 2026

Polymyxin B vs Theta-Defensin

Polymyxin B vs Theta-Defensin — mechanism, half-life, dosing, and research status compared. Which is right for your protocol?

Polymyxin B
Antimicrobial Peptide

Polymyxin B is a cyclic lipopeptide antibiotic from Bacillus polymyxa that was approved in the 1960s and fell out of favor due to nephrotoxicity, but has experienced a major clinical resurgence as a last-resort treatment for carbapenem-resistant Gram-negative infections (Acinetob...

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Theta-Defensin
Antimicrobial Peptide

Theta-defensins are the only known cyclic peptides produced in the animal kingdom. Found in rhesus macaques and other Old World primates, they are formed by ligation of two 9-residue alpha-defensin gene products into an 18-residue macrocyclic structure....

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Key Parameters
Parameter Polymyxin B Theta-Defensin
Category Antimicrobial Peptide Antimicrobial Peptide
Research FDA Approved Preclinical
Half-Life 6-8 hours Extended (cyclic stability)
Typical Dose 15,000-25,000 units/kg/day IV N/A (research only)
Frequency Every 12 hours IV N/A
Route IV / IM / Topical / Intrathecal Systemic (research)
FDA Status Approved (systemic Gram-negative infections) Not approved

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Frequently Asked Questions
What is the difference between Polymyxin B and Theta-Defensin?
Polymyxin B: Polymyxin B is a cyclic lipopeptide antibiotic from Bacillus polymyxa that was approved in the 1960s and fell out of favor due to nephrotoxicity, but has experienced a major clinical resurgence as a l... Theta-Defensin: Theta-defensins are the only known cyclic peptides produced in the animal kingdom. Found in rhesus macaques and other Old World primates, they are formed by ligation of two 9-residue alpha-defensin ge...
Which has a longer half-life, Polymyxin B or Theta-Defensin?
Polymyxin B half-life: 6-8 hours. Theta-Defensin half-life: Extended (cyclic stability).
Can you stack Polymyxin B and Theta-Defensin?
Polymyxin B and Theta-Defensin are in the same category and used together in research protocols. Always consult relevant literature and follow appropriate guidelines.

For research use only. Not medical advice. ASCEND does not conduct or endorse any specific research protocol. Always consult relevant scientific literature and regulatory guidelines.