Bacitracin

BRAND NAMES

Common brand names for bacitracin include Neosporin, Polysporin, Triple Antibiotic, and Baciguent. These products often combine bacitracin with other antibiotics to broaden their antibacterial coverage.

Combination products containing bacitracin:

Medi-Quik – another triple antibiotic formula

Mycitracin – older brand with bacitracin (often discontinued or regional)

MECHANISM OF ACTION

Bacitracin disrupts bacterial cell wall synthesis by blocking the dephosphorylation of a lipid carrier molecule responsible for transporting peptidoglycan precursors across the cell membrane. It binds to the pyrophosphate group on this lipid carrier, preventing its recycling. This interruption stops the construction of the bacterial cell wall, ultimately causing cell lysis.

PHARMACOKINETICS

Absorption

Bacitracin is poorly absorbed through intact skin and the gastrointestinal tract but is effectively absorbed when administered intramuscularly. However, topical bacitracin can be absorbed through damaged or burned skin, and systemic absorption may also occur following intra-abdominal use. Once absorbed, bacitracin distributes widely throughout the body, undergoes partial metabolism, and is primarily excreted by the kidneys.

Distribution

Although bacitracin distributes widely throughout the body after intramuscular (IM) injection, precise data on its volume of distribution in humans are limited. This lack of information is largely due to the infrequent use of systemic bacitracin, as it carries a high risk of toxicity.

Metabolism

Bacitracin is primarily metabolized into smaller peptides and amino acids through hydrolysis, with its breakdown and elimination varying depending on the route of administration. Due to its polypeptide structure, it is expected to be broken down by the body's proteases. 

Excretion

When administered intramuscularly, bacitracin is primarily excreted by the kidneys, with about 87% of the dose eliminated in the urine within 6 hours. In contrast, after oral administration, bacitracin is poorly absorbed and is mainly excreted in the feces, as it acts locally within the intestines rather than systemically.

PHARMACODYNAMICS

Bacitracin's pharmacodynamics involve its role as a cell wall synthesis inhibitor, mainly targeting gram-positive bacteria. It works by blocking the dephosphorylation of a lipid carrier responsible for transporting peptidoglycan precursors across the bacterial cell membrane. Depending on the concentration, bacitracin can be either bacteriostatic or bactericidal. By disrupting cell wall formation, it ultimately leads to bacterial cell death.

ADMINISTRATION

Bacitracin is mainly used topically as an ointment for minor skin infections and as an eye ointment for bacterial eye infections. It’s poorly absorbed through intact skin but can be absorbed through damaged skin. Systemic use via intramuscular injection is rare due to kidney toxicity risks, with most of the drug excreted in urine. Oral use is uncommon and acts locally in the gut, as it’s poorly absorbed and excreted in feces.

DOSAGE AND STRENGTH

Topical ointment: 

Bacitracin ointment is a common OTC product used to help prevent infection in minor cuts, scrapes, and burns. A typical strength is 500 units per gram (500 units/g). It is generally applied to the affected area.

Ophthalmic (eye) ointment:

For treating certain eye infections, a sterile ophthalmic ointment form of bacitracin is available. This form is typically 500 units/g. A small amount of ointment is applied to the eye. Follow the directions of a healthcare professional for frequency and duration of application.

Intramuscular (IM) injection:

This form of bacitracin is used for treating serious systemic infections when caused by susceptible bacteria. Its use is less common now due to the potential for kidney damage and the availability of alternative treatments. It is typically provided in vials for reconstitution. Dosage is determined by a healthcare professional based on factors such as the patient's age and weight. The injectable form is intended for intramuscular use only. 

FOOD INTERACTIONS

Bacitracin generally has minimal to no significant food interactions because it is mostly used topically or poorly absorbed when taken orally. Since it acts locally on the skin or in the intestines (when given orally), food does not typically affect its effectiveness or absorption.

However, if bacitracin is used systemically (which is rare), there are no well-documented food interactions, but it’s always best to follow your healthcare provider’s advice.

DRUG INTERACTIONS

Serious drug interactions with bacitracin mainly arise with its intramuscular form, which is seldom used today because of the high risk of nephrotoxicity. When administered systemically, bacitracin should not be combined with other medications that can harm the kidneys. In contrast, topical bacitracin ointments have minimal systemic absorption and are associated with very few drug interactions.

CONTRAINDICATIONS

• Known hypersensitivity or allergy to bacitracin or any component of the formulation. Use should be avoided in patients with a history of allergic reactions to prevent severe hypersensitivity or anaphylaxis.

• Use in large areas of damaged skin or severe burns with caution, as increased systemic absorption can lead to toxicity.

• Intramuscular or systemic use is generally contraindicated or avoided due to the risk of nephrotoxicity.

• Use in patients with kidney impairment should be cautious if systemic administration is considered, due to potential accumulation and toxicity.

Topical bacitracin is generally safe when used as directed but should not be applied to deep puncture wounds, serious burns, or large open areas without medical supervision.

SIDE EFFECTS

• Skin irritation.

• Allergic contact dermatitis.

• Itching and hives.

• Swelling of the face, lips, tongue, or throat.

• Difficulty breathing or swallowing.

• Dizziness or fainting.

• Tightness in the chest.

• Acute kidney injury.

• Blood dyscrasias.

• Gastrointestinal issues.

OVERDOSE

• Stomach pain.

• Vomiting.

• Eye redness, pain, and itching (from eye contact).

Allergic reaction:

• Redness and itching of the skin.

• In severe cases, difficulty swallowing or breathing.

• Dizziness or fainting.

• Joint pain.

TOXICITY

Toxicity from topical bacitracin is uncommon but can still cause severe reactions in some cases. In contrast, systemic use, particularly via intramuscular injection, is linked to significant toxicity, including nephrotoxicity and renal failure. Topical toxicity symptoms may include skin rashes or allergic reactions, while ingesting large amounts can result in stomach upset. Severe systemic toxicity can lead to more serious complications such as bone marrow suppression and kidney failure.