Polymyxin B


Generic Medicine Info
Indications and Dosage
Intramuscular
Susceptible infections
Adult: 25,000-30,000 U/kg daily in divided doses 4-6 hrly. Max: 2,000,000 U/day.
Child: <2 yr 40,000 U/kg daily in divided doses 6 hrly (not routinely recommended due to pain at injection sites); ≥2 yr Same as adult dose but not routinely recommended due to pain at injection sites.

Intrathecal
Meningitis
Adult: 50,000 U once daily for 3-4 days, then on alternate days for at least 2 wk after CSF cultures are negative and CSF glucose content is normal. Max: 2,000,000 U/day.
Child: <2 yr 20,000 U once daily for 3-4 days or 25,000 U on alternate days, followed by the latter dose for at least wk after CSF cultures are negative and CSF glucose content is normal; ≥2 yr Same as adult dose.

Intravenous
Susceptible infections
Adult: 15,000-25,000 U/kg daily by continuous IV drip or intermittent infusion 12 hrly at 60-120 min duration. Max: 2,000,000 U/day.
Child: <2 yr 40,000 U/kg daily in divided doses 12 hrly; ≥2 yr Same as adult dose.

Ophthalmic
Ocular infections
Adult: As soln/oint w/ neomycin and dexamethasone: Soln: Instill 1-2 drops into affected eye up to 6 times daily, may be used hrly in severe cases. Oint: Apply a small amount into the conjunctival sac(s) up to 3-4 times daily.
Child: Same as adult dose.

Otic/Aural
Otic infections
Adult: As otic susp containing 3.5 mg neomycin base, 10,000 U and 10 mg hydrocortisone: Instill 4 drops into the affected ear canal 3-4 times daily for up to 10 days.
Child: As otic susp containing 3.5 mg neomycin base, 10,000 U and 10 mg hydrocortisone: Instill 3 drops into the affected ear canal 3-4 times daily for up to 10 days.

Subconjunctival
Ocular infections
Adult: Up to 100,000 U daily.

Topical/Cutaneous
Skin infections
Adult: As 0.1% soln or oint in combination other drugs: Apply onto affected area 1-3 times daily.
Child: Same as adult dose.
Renal Impairment
Intramuscular, Intravenous, Intrathecal:
Reduce dose. Max: 15,000 U/kg/day.
Reconstitution
Intravenous:
Dissolve 500,000 U in 300-500 mL of D5W for continuous IV drip, or intermittent infusion.
Intramuscular:
Dissolve 500,000 U in 2 mL sterile water for inj or NaCl 0.9% inj or 1% procaine HCl inj.
Intrathecal:
Dissolve 500,000 U in 10 mL NaCl 0.9% inj for 50,000 U/mL dosage unit.
Subconjunctival:
Dissolve 500,000 U in 20-50 mL sterile water for inj or NaCl 0.9% inj for a 10,000-25,000 U/mL concentration.
Incompatibility
Cloxacillin.
Contraindications
Hypersensitivity to polymyxins; perforated ear drums (otic). Concurrent use w/ nephrotoxic and/or neurotoxic drugs and neuromuscular blockers.
Special Precautions
Patients w/ pre-existing nitrogen retention. Renal impairment. Pregnancy and lactation.
Adverse Reactions
Facial flushing, fever, rash, pruritus, urticaria, skin exanthema, eosinophilia, dizziness, ataxia; severe pain at inj sites (IM), thrombophlebitis (IV) at inj sites. Ophth: ocular discomfort, keratitis, eye irritation.
Potentially Fatal: Nephrotoxicity, neurotoxicity (higher doses or in patients w/ renal impairment); resp paralysis, anaphylaxis, Clostridium difficile-associated diarrhoea and pseudomembranous colitis.
Ophth/Otic/Topical: C (FDA pregnancy category C applies to polymyxin B in combination w/ other drugs.)
Patient Counseling Information
Eye drop/oint may cause temporary blurred vision or other visual disturbances which may affect ability to drive or operate machinery.
Monitoring Parameters
Monitor renal function; neurologic symptoms; signs of superinfection.
Drug Interactions
Potentially Fatal: Additive neurotoxic or nephrotoxic effect w/ bacitracin, streptomycin, neomycin, kanamycin, gentamicin, tobramycin, amikacin, cephaloridine, paromomycin, viomycin, colistin. Increased risk of resp paralysis w/ neuromuscular blockers (e.g. anaesthetics, muscle relaxants).
Action
Description: Polymyxin B disrupts the bacterial cytoplasmic membrane of mostly gm-ve organisms allowing leakage of intracellular constituents by binding to membrane phospholipids.
Pharmacokinetics:
Absorption: Minimal from the GI tract except in infants (≤10% of a dose). Time to peak plasma concentration: W/in 2 hr (IM).
Distribution: Widely distributed; extensively bound to cell membranes in the tissues. Plasma protein binding: Low.
Excretion: Via urine (approx 60% as unchanged drug). Half-life: 6 hr.
Chemical Structure

Chemical Structure Image
Polymyxin B

Source: National Center for Biotechnology Information. PubChem Database. Polymyxin b, CID=49800004, https://pubchem.ncbi.nlm.nih.gov/compound/Polymyxin-b (accessed on Jan. 21, 2020)

Storage
Powd for inj: Store between 20-25°C. Protect from light. Reconstituted soln: Store between 2-8°C, stable for 72 hr. Do not store in alkaline soln. Ophth soln/oint: Store below 25°C. Otic soln: Store between 15-25°C. Topical soln/oint: Store between 15-25°C.
MIMS Class
Ear Anti-Infectives & Antiseptics / Eye Anti-Infectives & Antiseptics / Other Antibiotics / Topical Antibiotics
References
Anon. Polymyxin B. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 16/06/2015.

Bacitracin Zinc, Neomycin Sulfate and Polymyxin Sulfate Ointment. DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/06/2015.

Buckingham R (ed). Polymyxin B Sulfate. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 16/09/2015.

McEvoy GK, Snow EK, Miller J et al (eds). Polymyxin B Sulfate. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 16/06/2015.

Neomycin and Polymyxin B Sulfates and Hydrocortisone Solution. DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/06/2015.

Neomycin Sulfate, Polymyxin B sulfate and Gramicidin Solution/Drops. DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/06/2015.

Polymyxin B Sulfate Injection, Powder, for Solution. DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 17/06/2015.

Wickersham RM. Polymyxin B Sulfate. Facts and Comparisons [online]. St. Louis, MO. Wolters Kluwer Clinical Drug Information, Inc. https://www.wolterskluwercdi.com/facts-comparisons-online/. Accessed 17/06/2015.

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