Indications
Polymyxin B is an antibiotic used in two main ways:
- On the eye, ear or skin: in drops, ointments and creams, usually combined with other antibiotics or a steroid, to treat bacterial infections such as conjunctivitis, outer ear infection and infected skin wounds.
- By injection: in hospital, for serious infections caused by certain bacteria (gram-negative bacteria such as Pseudomonas and Acinetobacter) that do not respond to other antibiotics.
How It Works
Polymyxin B attaches to the outer wall of certain bacteria and damages it, so the contents leak out and the bacteria die. It does not work against viruses or fungi.
Dosage and Administration
- Eye, ear and skin products: use as prescribed or as directed on the pack, usually several times a day for a short course of about 5 to 7 days. Do not let the dropper or tube touch the eye, ear or skin.
- Injection: given by a doctor or nurse in hospital, into a vein or muscle. The dose is worked out from body weight and kidney function, as prescribed. Kidney tests are checked during treatment.
Finish the course as advised, even if you feel better.
Interactions
These matter mainly for the injection. The risk of kidney and nerve damage rises with other medicines that can harm the kidneys or nerves, such as aminoglycosides (for example Gentamicin and Amikacin), Vancomycin, Amphotericin B and Colistin. It can strengthen muscle relaxants and some anaesthetics, which can affect breathing. Tell the doctor about all medicines.
Contraindications
- Allergy to polymyxin B or any ingredient of the product.
- Ear drops: a perforated eardrum, unless a doctor advises otherwise (some combination ear drops can harm hearing).
Side Effects
Eye, ear and skin use: mild stinging, itching, redness or rash where applied.
Injection: kidney damage, numbness or tingling around the mouth or in the hands and feet, dizziness, pain at the injection site, fever and skin rash.
Get urgent medical help for: muscle weakness or difficulty breathing, passing much less urine, signs of a severe allergic reaction (swelling of the face, lips or throat, difficulty breathing, widespread rash), or with eye or ear use, pain, swelling or sudden loss of sight or hearing.
Pregnancy and Lactation
Eye, ear and skin products absorb very little and may be used in pregnancy and breastfeeding if a doctor advises. The injection should be used in pregnancy only when the infection is serious and no safer option exists. Ask the doctor before breastfeeding during injection treatment.
Precautions and Warnings
The injection needs close monitoring of kidney function, nerve symptoms and breathing; the dose is adjusted for kidney problems. Use of eye, ear or skin products for longer than advised can allow resistant germs or fungi to grow. Do not wear contact lenses while using eye products unless the doctor says it is safe. See a doctor if the infection does not improve within a few days.
Overdose
An overdose of the injection can cause kidney failure, nerve damage and breathing paralysis. It is treated in hospital with breathing support and other care. Overuse of eye, ear or skin products is unlikely to cause serious harm.
Therapeutic Class
Polymyxin antibiotic.
Storage
Eye, ear and skin products: store below 30°C, away from light and out of the reach of children; throw away eye drops 4 weeks after opening. Injection vials are usually kept in a fridge at 2 to 8°C and are stored and prepared by hospital staff.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.