Vancomycin is a powerful, "last-resort" glycopeptide antibiotic used to treat serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin was discovered in the 1950s as a powerful antibiotic against penicillin-resistant Staphylococcus. Initially, its use was limited due to perceived toxicity from impure early versions, which led to a condition nicknamed "Mississippi mud" for its brown color.
BRAND NAMES
Vancocin-It is offered in various formulations, including oral capsule form.
Firvanq- is specifically for vancomycin oral solution.
Tyzavan-it is in injection form.
MECHANISM OF ACTION
Vancomycin functions by binding to the D-alanyl-D-alanine ends of peptidoglycan precursors, blocking the transglycosylation and transpeptidation steps essential for bacterial cell wall synthesis. This disruption weakens the cell wall, ultimately causing bacterial cell death. Its activity is limited to gram-positive bacteria, as its large molecular size prevents it from penetrating the outer membrane of gram-negative organisms.
PHARMACOKINETICS
Absorption
Vancomycin has poor oral absorption, with less than 10% bioavailability in a normal, healthy gastrointestinal tract. It is a large, hydrophilic molecule that does not easily cross the intestinal wall into the bloodstream.
Distribution
Vancomycin is extensively distributed throughout body tissues and fluids, with a volume of distribution ranging from 0.4 to 1.0 L/kg. It has a protein binding rate of about 55%.
Metabolism
Vancomycin is minimally metabolized in the body and is mainly eliminated in its unchanged form. When administered intravenously, it is mainly eliminated via glomerular filtration in the kidneys, with up to 75% of the dose excreted in the urine. When taken orally, vancomycin is poorly absorbed by the intestines and therefore works locally within the gastrointestinal tract, where it is subsequently excreted in the feces.
Excretion
About 75-80% of an administered dose is excreted in the urine within the first 24 hours. Following intravenous administration, small amounts of vancomycin may be present in the bile and feces.
PHARMACODYNAMICS
Vancomycin pharmacodynamics refers to the relationship between the drug’s concentration in the body and its antimicrobial activity. The drug’s effectiveness is most accurately predicted by the ratio of the 24-hour area under the curve (AUC) to the minimum inhibitory concentration (MIC), aiming for an AUC/MIC of ≥ 400 to achieve successful clinical outcomes.
ADMINISTRATION
Vancomycin is administered either intravenously (IV) for serious systemic infections or orally for infections limited to the intestines. The correct route depends on the type and location of the infection, as vancomycin is poorly absorbed through the gut and is not effective orally for infections outside of the intestines.
DOSAGE AND STRENGTH
Vancomycin is available in two main dosage forms-
Oral capsules: Available in 125 mg and 250 mg strengths.
Oral solution or suspension: A liquid form for oral use.
DRUG INTERACTIONS
Vancomycin has notable drug interactions, especially with medications that can cause kidney damage or hearing damage. Co-administering vancomycin with other nephrotoxic drugs like aminoglycoside antibiotics, NSAIDs, and the antibiotic piperacillin-tazobactam significantly increases the risk of severe kidney injury. Other interactions include an increased effect of neuromuscular blockers used during anesthesia when combined with vancomycin, and a potential reduction in the effectiveness of certain live bacterial vaccines like the typhoid vaccine.
FOOD INTERACTIONS
Vancomycin has no known significant food interactions and can be taken with or without food. The specific use of vancomycin (oral vs. IV) is the key factor in how it works and what precautions are needed.
CONTRAINDICATIONS
The primary contraindication for vancomycin is a known hypersensitivity to the antibiotic, including severe reactions like anaphylaxis, Stevens-Johnson syndrome, and "Red Man Syndrome". Precautions and careful monitoring are necessary for patients with renal impairment, as vancomycin can cause nephrotoxicity, and those with pre-existing hearing loss, due to the risk of ototoxicity. Vancomycin solutions with dextrose should not be used in patients who have a corn allergy.
SIDE EFFECTS
Nephrotoxicity.
Hearing loss.
Severe skin reactions.
Low white blood cell count.
Injection site irritation.
Fever and chills.
Gastrointestinal issues.
Unpleasant taste in the mouth.
Headache.
Red Man Syndrome.
OVER DOSE
Acute kidney injury (AKI).
Ototoxicity.
Vertigo.
Hypotension.
Neurological symptoms.
Gastrointestinal issues.
Red Man Syndrome.
TOXICITY
Vancomycin toxicity results from excessively high doses, prolonged treatment, or reduced kidney function, leading to a build-up of the antibiotic in the bloodstream. In severe overdose cases, renal replacement therapy like hemodialysis may be necessary.