Bacitracin/polymyxin B

Bacitracin/Polymyxin B

Bacitracin and Polymyxin B are antibiotics commonly used in combination to treat bacterial infections, particularly those affecting the skin and eyes. This combination is often found in topical ointments and is known for its effectiveness against a variety of gram-positive and gram-negative bacteria.

Pharmacology

Bacitracin

Bacitracin is a polypeptide antibiotic that is primarily effective against gram-positive bacteria. It works by inhibiting bacterial cell wall synthesis, which ultimately leads to cell lysis and death. Bacitracin is often used topically due to its nephrotoxicity when administered systemically.

Polymyxin B

Polymyxin B is a cyclic peptide antibiotic that targets gram-negative bacteria. It disrupts the bacterial cell membrane by interacting with its phospholipids, leading to increased permeability and cell death. Polymyxin B is also used topically due to its potential for nephrotoxicity and neurotoxicity when used systemically.

Clinical Uses

The combination of Bacitracin and Polymyxin B is used in various topical formulations to treat superficial skin infections, minor cuts, scrapes, and burns. It is also used in ophthalmic preparations to treat bacterial conjunctivitis and other eye infections.

Mechanism of Action

The combination of Bacitracin and Polymyxin B provides a broad spectrum of antibacterial activity. Bacitracin targets gram-positive bacteria by inhibiting cell wall synthesis, while Polymyxin B targets gram-negative bacteria by disrupting cell membrane integrity. This dual action makes the combination effective against a wide range of bacterial pathogens.

Side Effects

Topical application of Bacitracin/Polymyxin B is generally well-tolerated. However, some individuals may experience allergic reactions, including rash, itching, or swelling at the site of application. Systemic absorption is minimal, reducing the risk of systemic side effects.

Resistance

Bacterial resistance to Bacitracin and Polymyxin B is relatively uncommon, but it can occur. Resistance mechanisms include alterations in the target sites, efflux pumps, and enzymatic degradation of the antibiotics.

Also see

• Antibiotic resistance
• Topical antibiotics
• Bacterial cell wall synthesis inhibitors
• Gram-positive bacteria
• Gram-negative bacteria