POLYMYXIN B SULFATE

POLYMYXIN B SULFATE
(pol-i-mix'in)
Classifications: antibiotic;
Therapeutic: antibiotic

Pregnancy Category: B

Availability

500,000 unit injection

Action

Antibiotic derived from strains of Bacillus polymyxa. Binds to lipid phosphates in bacterial membranes and, through cationic detergent action, changes permeability to permit leakage of cytoplasm from the bacterial cell, resulting in cell death.

Therapeutic Effect

Bactericidal against susceptible gram-negative but not gram-positive organisms.

Uses

Topically and in combination with other anti-infectives or corticosteroids for various superficial infections of eye, ear, mucous membrane, and skin. Concurrent systemic anti-infective therapy may be required for treatment of intraocular infection and severe progressive corneal ulcer. Used parenterally only in hospitalized patients for treatment of severe acute infections of urinary tract, bloodstream, and meninges; and in combination with Neosporin for continuous bladder irrigation to prevent bacteremia associated with use of indwelling catheter.

Contraindications

Hypersensitivity to polymyxin antibiotics; concurrent and sequential use of other nephrotoxic and neurotoxic drugs; concurrent use of skeletal muscle relaxants, ether, or sodium citrate; lactation. Safety in children <2 mo is not established.

Cautious Use

Impaired kidney function, renal failure; myasthenia gravis; pulmonary disease; pregnancy (category B).

Route & Dosage

Infections
Adult/Child: IV 15,000–25,000 U/kg/day divided q12h IM 25,000–30,000 U/kg/d divided q4–6h Intrathecal 50,000 U x 3–4 d then every other day;  >2 y, 20,000 U x 3–4 d, then 25,000 U every other day
Infant: IV/IM Up to 40,000 U/kg/d

Administration

Intramuscular
  • Routine administration by IM routes not recommended because it causes intense discomfort, along the peripheral nerve distribution, 40–60 min after IM injection.
  • Make IM injection in adults deep into upper outer quadrant of buttock. Select IM site carefully to avoid injection into nerves or blood vessels. Rotate injection sites. Follow agency policy for IM site used in children.
Intravenous

PREPARE: Intermittent: Reconstitute by dissolving 500,000 U in 5 mL sterile water for injection or NS to yield 100,000 U/mL. Withdraw a single dose and then further dilute in 300–500 mL of D5W.  

ADMINISTER: Intermittent: Infuse over period of 60–90 min. Inspect injection site for signs of phlebitis and irritation.  

INCOMPATIBILITIES Solution/additive: Amphotericin B, cefazolin, cephalothin, cephapirin, chloramphenicol, heparin, nitrofurantoin, prednisolone, tetracycline.

  • Protect unreconstituted product and reconstituted solution from light and freezing. Store in refrigerator at 2°–8° C (36°–46° F). Parenteral solutions are stable for 1 wk when refrigerated. Discard unused portion after 72 h.

Adverse Effects (≥1%)

Body as a Whole: Irritability, facial flushing, ataxia, circumoral, lingual, and peripheral paresthesias (stocking-glove distribution); severe pain (IM site), thrombophlebitis (IV site), superinfections, electrolyte disturbances (prolonged use; also reported in patients with acute leukemia); local irritation and burning (topical use), anaphylactoid reactions (rare). CNS: Drowsiness, dizziness, vertigo, convulsions, coma; neuromuscular blockade (generalized muscle weakness, respiratory depression or arrest); meningeal irritation, increased protein and cell count in cerebrospinal fluid, fever, headache, stiff neck (intrathecal use). Special Senses: Blurred vision, nystagmus, slurred speech, dysphagia, ototoxicity (vestibular and auditory) with high doses. GI: GI disturbances. Urogenital: Albuminuria, cylindruria, azotemia, hematuria.

Interactions

Drug: anesthetics and neuromuscular blocking agents may prolong skeletal muscle relaxation. aminoglycosides and amphotericin B have additive nephrotoxic potential.

Pharmacokinetics

Peak: 2 h IM. Distribution: Widely distributed except to CSF, synovial fluid, and eye; does not cross placenta. Metabolism: Unknown. Elimination: 60% excreted unchanged in urine. Half-Life: 4.3–6 h.

Nursing Implications

Assessment & Drug Effects

  • Lab tests: Obtain C&S tests prior to first dose and periodically thereafter to determine continuing sensitivity of causative organisms. Perform baseline serum electrolytes and kidney function tests before parenteral therapy. Frequent monitoring of kidney function and serum drug levels is advised during therapy. Monitor electrolytes at regular intervals during prolonged therapy.
  • Review electrolyte results. Patients with low serum calcium and low intracellular potassium are particularly prone to develop neuromuscular blockade.
  • Inspect tongue every day. Assess for S&S of superinfection (see Appendix F). Polymyxin therapy supports growth of opportunistic organisms. Report symptoms promptly.
  • Monitor I&O. Maintain fluid intake sufficient to maintain daily urinary output of at least 1500 mL. Some degree of renal toxicity usually occurs within first 3 or 4 d of therapy even with therapeutic doses. Consult physician.
  • Withhold drug and report findings to physician for any of the following: Decreases in urine output (change in I&O ratio), proteinuria, cellular casts, rising BUN, serum creatinine, or serum drug levels (not associated with dosage increase). All can be interpreted as signs of nephrotoxicity.
  • Nephrotoxicity is generally reversible, but it may progress even after drug is discontinued. Therefore, close monitoring of kidney function is essential, even following termination of therapy.
  • Be alert for respiratory arrest after the first dose and also as long as 45 d after initiation of therapy. It occurs most commonly in patients with kidney failure and high plasma drug levels and is often preceded by dyspnea and restlessness.

Patient & Family Education

  • Report to physician immediately any muscle weakness, shortness of breath, dyspnea, depressed respiration. These symptoms are rapidly reversible if drug is withdrawn.
  • Stop drug administration immediately and report to physician if you experience eyelid irritation, itching, and burning with ophthalmic drops.
  • Report promptly to physician transient neurologic disturbances (burning or prickling sensations, numbness, dizziness). All occur commonly and usually respond to dosage reduction.
  • Report promptly to physician the onset of stiff neck and headache (possible symptoms of neurotoxic reactions, including neuromuscular blockade). This response is usually associated with high serum drug levels or nephrotoxicity.
  • Report promptly S&S of superinfection (see Appendix F).

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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