Side-by-Side Comparison · 2026

Colistin vs Theta-Defensin

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

Colistin
Antimicrobial Peptide

Colistin (polymyxin E) is a cyclic lipopeptide antibiotic structurally related to polymyxin B, differing in the fatty acid chain and one amino acid residue. Like polymyxin B, colistin targets LPS and disrupts outer membranes of Gram-negative bacteria....

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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 Colistin Theta-Defensin
Category Antimicrobial Peptide Antimicrobial Peptide
Research FDA Approved Preclinical
Half-Life Colistimethate (prodrug): 2-3 hours; active colistin: 14 hours Extended (cyclic stability)
Typical Dose 2.5-5 mg/kg/day CBA IV N/A (research only)
Frequency Every 8-12 hours N/A
Route IV (colistimethate) / Inhaled / Topical Systemic (research)
FDA Status Approved (systemic Gram-negative infections) Not approved

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Frequently Asked Questions
What is the difference between Colistin and Theta-Defensin?
Colistin: Colistin (polymyxin E) is a cyclic lipopeptide antibiotic structurally related to polymyxin B, differing in the fatty acid chain and one amino acid residue. Like polymyxin B, colistin targets LPS and ... 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, Colistin or Theta-Defensin?
Colistin half-life: Colistimethate (prodrug): 2-3 hours; active colistin: 14 hours. Theta-Defensin half-life: Extended (cyclic stability).
Can you stack Colistin and Theta-Defensin?
Colistin 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.