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Antibiotics - Polymyxins: Nursing Pharmacology

Notes

Notes

ANTIBIOTICS: POLYMYXINS
DRUG NAME
polymyxin B; polymyxin E (Coly-Mycin M)
*High Alert Medications*

CLASS
Antibiotics (Polymyxins)
MECHANISM OF ACTION
Damage and disrupt bacterial membrane → bacterial cell death
INDICATIONS
Last resort for multi-resistant gram-negative bacteria: Echerichia coli, Pseudomonas aeruginosa, Klebsiella spp. and Shigella spp.
ROUTE(S) OF ADMINISTRATION
  • IM, IV, INH
  • Polymyxin B: intrathecal, ophthalmic
SIDE EFFECTS
  • Fever, rash, itching (IV administration)
  • Headache, neck stiffness (intrathecal polymyxin B)
  • Neurotoxicity and nephrotoxicity (boxed warning for polymyxin B)
CONTRAINDICATIONS AND CAUTIONS
  • Pregnancy and breastfeeding
  • Renal disease
  • Neuromuscular disease
  • Drug interactions:
    • Aminoglycosides (boxed warning for polymyxin B)
    • General anesthetics and neuromuscular blocking agents
NURSING CONSIDERATIONS
Assessment and monitoring: polymyxin B
Assessment
  • Weight
  • Vital signs, SpO2
  • Respiratory status
  • Fluid intake and output
  • Laboratory test results: CBC, renal function tests, urinalysis, culture and sensitivity results, ABGs
  • Diagnostic test results: chest X-ray or CT scan

Monitoring / interventions
  • Ensure adequate hydration
  • Urinary catheter
  • Patent IV
  • Confirm correct dose: units per kilogram and mL/hr to by infusion pump
  • Monitor insertion site for extravasation
  • Assess for neurotoxicity, nephrotoxicity
  • Evaluate therapeutic response: absence of fever and dyspnea; infection resolution

Client education
  • Purpose of medication: treatment for pneumonia
  • IV administration: loading dose; then every 12 hours
  • Report: drowsiness, dizziness, paresthesias
Memory Anchors and Partner Content
Transcript

Polymyxins are an older class of antibiotics, which are nowadays used as a last resort to treat bacterial infections when other antibiotics are either contraindicated or ineffective.

These medications affect susceptible gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella spp., and Shigella spp.

There are two approved medications in this class: polymyxin B and polymyxin E, also known as colistin. Both are available for intramuscular and intravenous use.

Additionally, polymyxin B can be given intrathecally, as an ophthalmic formulation, as well as by inhalation.

Once administered, polymyxins work by binding to the bacterial membrane and disrupting it, which ultimately leads to bacterial cell death.

Now, polymyxins can cause serious side effects like neurotoxicity and nephrotoxicity. In fact, that’s a boxed warning for polymyxin B!

Clients with neurotoxicity might experience facial flushing, drowsiness, dizziness, ataxia, and paresthesia. Sometimes, neurotoxicity can cause respiratory paralysis.

On the other hand, nephrotoxicity may present with a low urine output, albuminuria, cellular casts in the urine, and azotemia.

Finally, specific side effects associated with intravenous administration of polymyxins include fever, rash, and itching; while side effects of intrathecal polymyxin B use include headaches and neck stiffness.

Regarding contraindications, polymyxins should not be used during pregnancy and breastfeeding, as their safety hasn't been established.

These medications should be used cautiously in elderly clients, as well as in those with neuromuscular disease like myasthenia gravis, and in clients with renal disease.

Finally, polymyxins should not be combined with other neurotoxic or nephrotoxic medications, such as aminoglycosides. And again, that’s a boxed warning for polymyxin B!

Also, polymyxins shouldn't be used with general anesthetics and neuromuscular blocking agents, such as succinylcholine, rocuronium, vecuronium, and atracurium, as they can increase the risk of respiratory paralysis.

Now, when a client is diagnosed with hospital-acquired pneumonia and is prescribed polymyxin B, first, perform a baseline assessment including weight, vital signs, SpO2, respiratory status, as well as their fluid intake and output.

Next, review recent laboratory test results, specifically CBC, renal function tests, urinalysis, culture and sensitivity results, and arterial blood gas analysis.

Sources
  1. "Pharmacology" Elsevier Health Sciences (2014)
  2. "Polymyxins Revisited" Clinical Microbiology Reviews (2008)
  3. "Polymyxin B (Systemic, Topical)"  (25 Aug 2021)
  4. "Colistimethate"  (22 Mar 2021)
  5. "Focus on Nursing Pharmacology" LWW (2019)
  6. "Lehne's Pharmacology for Nursing Care" Elsevier Health Sciences (2014)
  7. "Polypeptide Antibiotics: Bacitracin, Colistin, Polymyxin B"  (May 2020)
  8. "International Consensus Guidelines for the Optimal Use of the Polymyxins: Endorsed by the American College of Clinical Pharmacy (ACCP), European Society of Clinical Microbiology and Infectious Diseases (ESCMID), Infectious Diseases Society of America (IDSA), International Society for Anti‐infective Pharmacology (ISAP), Society of Critical Care Medicine (SCCM), and Society of Infectious Diseases Pharmacists (SIDP)" Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy (2019)