Peptide Profile
Polymyxin B
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
Dose Range
1.5-2.5mg/kg
Frequency
Multiple times daily
Route
Intravenous infusion (primary systemic route)
Cycle Length
4-6 weeks
Onset
Rapid (hours to days)
Evidence
Strong
Compound Profile
Scientific & Efficacy Data
C₅₆H₉₈N₁₆O₁₃ (polymyxin B₁ free base)
Molecular Formula
1,203.5 g/mol (free base); ~1,385 g/mol (sulfate salt)
Molecular Weight
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
Half-Life
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
Bioavailability
1405-20-5 (polymyxin B sulfate)
CAS #
49800004
PubChem ID ↗
Developed By · 1947 (discovery); 1964 (FDA approval); 2000s (clinical resurgence for MDR Gram-negatives)
Bacillus polymyxa (natural source); Colistin Industries
Colistin Industries / Hospira Pharmaceuticals
Primary Benefits
Amino Acid Sequence
Dab-Dab-Dab-Phe-Dab-Phe-Dab-Asp-Dab-Dab (cyclic with fatty acid)Dosing
How much
do I take?
Starting Dose
Loading dose 2.0-2.5 mg/kg IV over 1 hour
Polymyxin B dosing begins with a loading dose to rapidly achieve therapeutic concentrations. Administer as IV infusion over 1-2 hours to minimize histamine-related infusion reactions. Calculate dose based on actual body weight (not ideal body weight). Pre-medication with antihistamine may reduce infusion reactions. Obtain baseline renal function (serum creatinine, BUN) before starting. This is an FDA-approved antibiotic — used under physician supervision in hospital settings.
Standard Dose
1.25-1.5 mg/kg IV every 12 hours (maintenance)
Standard maintenance dosing for serious systemic Gram-negative infections. Infuse over 1-2 hours. Monitor renal function (creatinine, BUN, urine output) at least every 48 hours. Target AUC₀₋₂₄ of 50-100 mg·h/L guided by TDM when available. Dose adjust for renal impairment per institutional guidelines. Combine with a second agent (carbapenem, rifampicin, or minocycline) for XDR infections. Duration guided by clinical response and source control.
Advanced Dose
Intrathecal: 5 mg/day; Inhaled: 2.5 mg/kg/day divided q12h; Topical: 10,000-25,000 units/g ointment
Specialized administration routes for specific indications. Intrathecal/intraventricular: 5 mg (50,000 units) daily for MDR Gram-negative meningitis/ventriculitis, preservative-free formulation required. Inhaled/nebulized: adjunct to IV therapy for MDR pneumonia. Topical: component of triple antibiotic ointment (Neosporin) for wound prophylaxis — safe for external use with minimal systemic absorption. All specialized routes require infectious disease specialist guidance.
Timing
Best time to take
Polymyxin B 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 Polymyxin B is not dependent on meal timing. Your healthcare team will provide specific instructions regarding food and fluid intake around treatment sessions.
If stacking
Polymyxin B 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.
Adjusting Your Dose
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
Calculate Your Exact Dose
Step 1: Peptide Weight
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Suitability
Is this
right for me?
Best For
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.
Consider Alternatives If
Who Should Avoid
Do not use if
- ×Known hypersensitivity to polymyxin B or polymyxin E (colistin)
- ×Severe pre-existing renal failure without dialysis support — nephrotoxicity may be life-threatening
- ×Concurrent use of other nephrotoxic agents (aminoglycosides, vancomycin, amphotericin B) without renal monitoring — additive nephrotoxicity risk
- ×Myasthenia gravis — polymyxin B can exacerbate neuromuscular blockade and precipitate respiratory failure
Use with caution if
- !You are taking other medications—discuss potential interactions with your healthcare provider
- !You have a history of liver or kidney disease
- !You are elderly or have multiple medical conditions
- !You are planning surgery in the near future—inform your surgeon about Polymyxin B use
- !You have any chronic health conditions that require regular monitoring
Administration
How do I
use it?
Reconstitution
What you need
- •Polymyxin B vial (lyophilized powder or solution)
- •Bacteriostatic water or sterile sodium chloride for reconstitution
- •Alcohol swabs for cleaning vial tops and injection sites
- •Appropriately sized syringes with fine-gauge needles (27-30 gauge)
- •Sharps disposal container
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
- •Abdomen (stomach area)—at least 2 inches from the belly button, most popular choice for self-injection
- •Front of thighs—middle to upper portion of the outer leg
- •Back of upper arm—outer area (may need assistance from another person)
Technique
- 1.Wash your hands thoroughly with soap and water before handling supplies
- 2.Clean the injection site with an alcohol swab and let it air dry completely
- 3.Pinch a fold of skin at the chosen injection site
- 4.Insert the needle at a 45-90 degree angle (depending on needle length and body composition)
- 5.Inject the medication slowly and steadily over 5-10 seconds
- 6.Release the skin fold and remove the needle, applying gentle pressure with a clean swab
- 7.Rotate injection sites to prevent tissue irritation or lipodystrophy
- 8.Dispose of the needle safely in a sharps container—never recap or reuse needles
Storage
Signs of degradation
Sample Daily Schedule
Safety
Is it
safe?
Safety Profile
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.
Clinical pharmacokinetic studies document polymyxin B mechanism through lipopolysaccharide binding (LPS) neutralization assays. Renal safety monitoring via creatinine clearance and cystatin C shows dose-dependent decline in GFR. Neurotoxicity correlates with serum levels >5 mg/L; electromyography studies show reversible neuromuscular junction effects. Meningitis studies show CSF penetration adequate for bacterial killing despite narrow therapeutic window.
Common Side Effects
Experienced by some users
Nephrotoxicity
Acute kidney injury reported in 34-60% of patients receiving IV polymyxin B. Manifests as rising serum creatinine, decreased urine output, and renal tubular injury. Typically appears within the first week of treatment. Risk increases with higher doses, longer duration, and concurrent nephrotoxic agents.
Management: Monitor renal function (creatinine, BUN, urine output) every 24-48 hours. Ensure adequate hydration. Avoid concurrent nephrotoxins when possible. Dose-adjust or switch agents if creatinine rises >2x baseline. Nephrotoxicity is usually reversible upon discontinuation.
Infusion-related histamine release
Flushing, pruritus, urticaria, chest tightness, and hypotension during IV infusion. Caused by direct polymyxin B-induced mast cell degranulation and histamine release. Dose-rate dependent.
Management: Infuse slowly over 1-2 hours (never IV push). Pre-medicate with diphenhydramine or H1-blocker if prior reaction. Reduce infusion rate if symptoms occur. Usually manageable without discontinuation.
Neurotoxicity
Perioral paresthesias (numbness/tingling around mouth), peripheral paresthesias in extremities, dizziness, and vertigo in 5-15% of patients. Dose-dependent and usually reversible.
Management: Monitor for neurological symptoms daily. Usually mild and self-limiting. Dose reduction may be needed if symptoms are significant. Resolves after treatment completion.
Skin hyperpigmentation
Progressive skin darkening, particularly in sun-exposed areas and head/neck region, with prolonged IV polymyxin B courses. Related to histamine-mediated stimulation of melanogenesis. Reported in 8-15% of patients.
Management: Cosmetic concern — not medically dangerous. Usually reversible over weeks to months after discontinuation. Sun protection may help minimize progression.
Less Common
- •Neuromuscular blockade
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 Polymyxin B
- ×Pregnancy or planning to become pregnant (unless specifically approved for use during pregnancy)
- ×Abnormal lab results or clinical markers that suggest adverse effects
Polymyxin B 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.
Interactions
With other peptides
- ✓May be used together under medical guidance.
- ✓May be used together under medical guidance.
- ✓May be used together under medical guidance.
With medications
- !Aminoglycosides (gentamicin, tobramycin, amikacin) — additive nephrotoxicity and neurotoxicity; use combination only when absolutely necessary with intensive renal monitoring - Use with caution—discuss with your healthcare provider.
- !Vancomycin at full doses — additive nephrotoxicity; if combination needed, monitor renal function daily - Use with caution—discuss with your healthcare provider.
- !Neuromuscular blocking agents (succinylcholine, vecuronium) — polymyxin B potentiates neuromuscular blockade, risk of prolonged paralysis and respiratory failure - Use with caution—discuss with your healthcare provider.
With supplements
- ✓Multivitamins - Generally safe to take alongside Polymyxin B. 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.
Effectiveness
Does it
work?
Evidence Level
Strong human trials
What to Expect
Hours 0-24 (loading and early treatment)
What you might notice
- •Infusion-related reactions (flushing, pruritus) during IV administration
- •Rapid bactericidal activity begins within hours of achieving therapeutic levels
- •Perioral tingling or numbness may appear within first 24 hours
- •Baseline laboratory values established for monitoring
What's normal
- •Loading dose rapidly achieves therapeutic serum concentrations
- •Infusion reactions are common and manageable with slow infusion rate
- •Mild paresthesias are expected and dose-related
- •Blood cultures should be repeated at 48-72 hours to assess microbiological response
What's next
- →Transition to maintenance dosing (1.25-1.5 mg/kg q12h)
- →Monitor renal function within 24-48 hours of initiation
- →Assess clinical response (fever, hemodynamics, WBC) at 48-72 hours
- →Obtain TDM if available to guide dose optimization
Days 2-7 (active treatment)
What you might notice
- •Clinical improvement: defervescence, improving hemodynamics, decreasing WBC
- •Negative blood cultures (typically by day 3-5 if effective)
- •Possible rise in serum creatinine — nephrotoxicity often appears in first week
- •Skin hyperpigmentation may begin to appear with prolonged IV therapy
What's normal
- •Microbiological clearance should occur within 3-5 days if organism is susceptible
- •Mild creatinine rise is common and requires close monitoring but not necessarily dose change
- •Neurotoxic symptoms typically stabilize at a given dose
- •Combination therapy should show synergistic effects by this point
What's next
- →Continue treatment for total 7-14 days guided by infection type and clinical response
- →Renal function monitoring at least every 48 hours
- →De-escalate or stop polymyxin B as soon as clinically appropriate
- →Assess source control and repeat imaging if needed
Week 2-4 (completion and recovery)
What you might notice
- •Infection resolved — treatment typically completed at 7-14 days
- •Renal function recovery begins after discontinuation (may take 1-4 weeks)
- •Neurological symptoms resolve over days to weeks after stopping
- •Skin hyperpigmentation gradually fades over weeks to months
What's normal
- •Nephrotoxicity is usually reversible — creatinine should trend toward baseline after stopping
- •Full renal recovery may take 2-4 weeks in some patients
- •Neurotoxicity resolves completely in most patients after discontinuation
- •Post-treatment surveillance for infection relapse is standard practice
What's next
- →Complete any required follow-up cultures to confirm cure
- →Monitor renal function until return to baseline
- →Antimicrobial stewardship review for future infection prevention
- →Address underlying risk factors for MDR infection (ICU stay, invasive devices)
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 Polymyxin B over time
- ✓Reduction in symptom frequency or severity
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
"Polymyxins: pharmacology, pharmacokinetics, pharmacodynamics, and clinical applications"
Zavascki AP, Goldani LZ, Li J, Nation RL, 2007
Finding: Inhaled polymyxin B effectively treated pneumonia caused by multidrug-resistant Gram-negative bacteria when intravenous treatment had failed, achieving cure or improvement in 95% of cases.
View Study"Nephrotoxicity associated with intravenous polymyxin B: a systematic review and meta-analysis"
Rigatto MH, Behle TF, Falci DR, Freitas T, Lopes NT, Nunes M, 2015
Finding: Research (2015) on polymyxin b contributes important scientific knowledge about its biological and pharmacological properties.
View Study"Therapeutic drug monitoring of polymyxin B: target exposure and optimal dosing strategies"
Tsuji BT, Pogue JM, Zavascki AP, Paul M, Daikos GL, Forrest A, 2019
Finding: Research (2019) on polymyxin b contributes important scientific knowledge about its biological and pharmacological properties.
View Study"Polymyxin B for the treatment of multidrug-resistant Gram-negative infections: clinical outcomes and resistance mechanisms"
Elias LS, Konzen D, Krebs JM, Zavascki AP, 2010
Finding: Study (2010) elucidates the molecular mechanism of action and biological pathways by which polymyxin b produces therapeutic effects.
View Study"Polymyxin combination therapy for carbapenem-resistant organisms: systematic review and network meta-analysis"
Ni W, Han Y, Liu J, Wei C, Zhao J, Cui J, Wang R, Liu Y, 2022
Finding: Clinical evidence (2022) supports the therapeutic use of polymyxin b in medical treatment protocols.
View StudyFrequently Asked Questions