Polymyxin: Types, uses, Dosage and Side Effects

Polymyxin B is a polymyxin antibiotic used to cure bacterial infections. It is ineffective against colds, measles, and other viral infections. The medication is mainly used to treat various infections, including urinary tract infections, meningitis, blood infections, and eye infections.

Polymyxin B Tablet Uses

Polymyxin B is used to treat and prevent minor skin infections caused by small wounds, scrapes, or burns. It is not suitable for large areas of the body. Consult your doctor before using this medication for skin injuries or diseases. This product contains antibiotics neomycin, bacitracin, and polymyxin, which work by preventing bacteria from growing. It is only effective against bacterial skin infections and is ineffective against other types of skin infections (e.g., fungal or viral infections).

Conditions Polymyxin B Tablet Treats

• Severe Pseudomonas aeruginosa infections
• Acinetobacter baumannii bloodstream infections
• Klebsiella pneumoniae pneumonia
• Meningitis caused by susceptible Gram-negative bacteria
• Complicated urinary tract infections from resistant organisms

Secondary Uses of Polymyxin B

• Topical skin infections, often combined with neomycin
• Bacterial conjunctivitis as an ophthalmic drop
• Prophylaxis of meningitis in neurosurgical procedures
• Inhalation therapy for cystic fibrosis patients with Pseudomonas
• Part of the combination regimens against multidrug-resistant infections

How Does Polymyxin B Work?

Mechanism of Action

Polymyxin B attaches to and disrupts the outer membrane of Gram-negative bacteria, causing the cell contents to leak out and leading to bacterial death. It targets lipopolysaccharides and phospholipids in the bacterial cell wall, which human cells do not possess, making it effective against resistant infections.

Hormone Interaction and Nervous System Action

Polymyxin B does not interact with human hormones. At therapeutic doses, it has a minimal effect on the human nervous system. However, high systemic levels can cause neurotoxicity, leading to symptoms like dizziness or tingling. This is due to interference with nerve cell membranes, so patients are monitored for nervous system side effects.

Polymyxin B Dosage

Typical Dosage Instructions (as per doctor's advice)

For intravenous use, the dose is weight-based, typically 1.5 to 2.5 mg/kg/day, divided into two doses every 12 hours, and adjusted for kidney function. For topical use (skin or eyes), follow the specific ointment or drop instructions commonly applied two to four times daily. Always use the exact dose and duration prescribed by your physician.

What Should I Do If I Miss a Dose?

If you miss an intravenous dose of Polymyxin B, take it as soon as you remember unless it's within 4 hours of the next dose. In that case, skip the missed dose and resume your regular schedule. Do not double up. For topical or ophthalmic forms, apply the missed application as soon as you recall, then continue normally without additional applications.

What Happens If an Overdose?

An overdose of Polymyxin B can lead to severe kidney damage and neurotoxic effects, such as muscle weakness, difficulty breathing, dizziness, or numbness. If an overdose is suspected, seek emergency medical care immediately. Treatment focuses on stopping Polymyxin B, providing supportive care (e.g., hydration, electrolyte monitoring), and addressing kidney and nerve function until recovery.

Polymyxin Side Effects

Polymyxin antibiotics may cause kidney toxicity and nerve damage because they disrupt cell membranes, not only of bacteria but also of human cells, especially in the kidneys and nerves. High doses or prolonged use increase the risk of these effects.

Common side effects of Polymyxin B include:

• Burning sensation
• Eye irritation
• Pain
• Redness
• Swelling at the injection site
• Flushing
• Dizziness
• Drowsiness
• Fever
• Headache
• Back pain
• Stiff neck
• Unsteadiness
• Hives
• Rash

While under treatment, if side effects persist or worsen, contact your doctor immediately.

Precautions

Before using Polymyxin B, inform your doctor if you are allergic to it or any related medications. The medication may contain inactive ingredients that can cause serious allergic reactions or other problems. Also, discuss your medical history with your doctor, especially if you have:

• Kidney disease
• Stomach ulcers or abdominal pain

Possible Interactions with Other Medications (Drug Interactions)

Overview of Drug Interactions

Polymyxin B can increase nephrotoxicity when given with other kidney-damaging drugs such as aminoglycosides (e.g., gentamicin), vancomycin, amphotericin B, or cyclosporine. Concurrent use with neuromuscular blockers (e.g., pancuronium) may enhance neuromuscular blockade, leading to muscle weakness or respiratory depression. Inform your doctor about all medications you take so they can adjust doses and monitor kidney function closely.

Possible Impact When Combined with Supplements or Herbal Products

• High-Dose Vitamin C or Herbal Diuretics: Supplements like vitamin C or herbs such as dandelion may stress the kidneys; combining them with polymyxin B can further increase the risk of renal damage.
• St. John's Wort: Although not directly interacting, it may induce liver enzymes and alter levels of co-administered drugs, potentially impacting overall treatment.
• Herbal Neuromuscular Agents (e.g., kava, valerian): These may potentiate neuromuscular blockade effects, increasing the chance of weakness or respiratory difficulties.
• Probiotics: Generally safe and may help restore gut flora; take them a few hours apart to avoid any theoretical reduction in antibiotic concentration in the gut.

How Should Polymyxin B Be Stored?

Recommended Storage Temperature for Polymyxin B

Store polymyxin B vials or bottles in their original packaging at room temperature, ideally between 20 °C and 25 °C (68 °F and 77 °F). Short excursions between 15 °C and 30 °C (59 °F and 86 °F) are acceptable. Keep the container tightly closed to protect from moisture and light.

What Happens If Polymyxin B Is Not Stored Properly?

• Reduced Potency: Exposure to heat or humidity can degrade the active ingredient, making treatments less effective and increasing the risk of treatment failure.
• Physical Changes: Capsules or solutions may discolour, become cloudy, or precipitate, leading to inaccurate dosing and potential safety issues.
• Contamination Risk: Storing in damp or unsanitary environments can encourage microbial growth, which poses infection risks if the medication is administered.

Polymyxin B vs Colistin

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