Vancomycin is an antibiotic that has been around for the last forty years. Recently however, vancomycin has been increasing in popularity because of its effectiveness in treating resistant organisms.
Introduction:Vancomycin is an antibiotic that has been around for the last forty years. Recently however, vancomycin has been increasing in popularity because of its effectiveness in treating resistant organisms. One of two glycopeptide antibiotics in clinical use, vancomycin has a unique chemical structure. Vancomycin is comprised of a glycosylated hexapeptide chain containing unusual amino acids. In addition, vancomycin is fairly rigid because of aromatic rings that are halogenated and crosslinked by aryl ether bonds. Vancomycin is able to penetrate the gram positive cell wall and therefore is effective against gram positive organisms. Vancomycin shows no activity against gram negative organisms however, because it is unable to penetrate the gram negative cell wall.
Mechanism of Action:Vancomycin acts by inhibiting bacterial cell wall biosynthesis. Specifically, vancomycin binds to the D-Alanyl-D-Alanine portion of the dipeptide, a key component for the transpeptidase reaction, and forms three hydrogen bonds. By covering the substrate for cell wall transaminase, vancomycin prevents the molecule from being transported to the cell wall. Cross linking does not occur and the integrity of the bacterial cell wall is compromised. The bacterial cell cannot withstand changes in osmotic pressure and it will rupture and die. Vancomycin is bactericidal.
Resistance:Resistance to vancomycin is a fairly recent phenomenon. Bacterial resistance develops when one position in the D-Ala binding site structure is changed from a NH to an O. The presence of an O prevents the formation of one of the three essential hydrogen bonds. Vancomycin cannot tightly cover the substrate and bacterial cell wall biosynthesis continues. Since Vancomycin has not been widely used in the clinical setting, it had been proposed that the resistance that is being seen is a result of overuse of a structurally similar antibiotic, Avoparin, in the US agricultural setting..
Future of Vancomycin:Vancomycin is currently used as an "antibiotic of last resort" in the clinical setting. The emergence of resistance is extremely troubling since, at present, there are no antibiotic alternatives of vancomycin's utility. In the event of widespread vancomycin resistance, some bacterial infections would, once again, become untreatable. In order to minimize the spread of resistance, infection control policies in hospitals are essential to ensure the appropriate use of vancomycin. In addition, the use of Avoparin, or other similar analogs, in the agricultural setting should be seriously reconsidered.
Important Dispensing Information for Vancomycin:Clinical Use of Vancomycin:Vancomycin is FDA approved for the treatment several bacterial infections, including infections caused by susceptible staphylococcus, streptococcus, enterococcus, and diphtheroid organisms. Vancomycin is commonly used in clinical practice to treat endocarditis and meningitis.
Dose and Dosage Forms:Vancomycin is available for both oral and intravenous administration. Orally, vancomycin is available as 125 mg and 250 mg capsules. Vancomycin is also available as a powder for use as a suspension in 250 mg/ml and 500 mg/6 ml concentrations. For intravenous administration, vancomycin is available in 1 gm, 5 gm, 10 gm, and 500 mg preparations. It is important to note that vancomycin is renally eliminated and requires dose adjustment in patients with renal impairment.
Adverse Effects:The most common side effects associated with vancomycin include nausea and vomiting. Rarely, nephrotoxicity, ototoxicity, and neutropenia may occur.
Drug Interactions:Many drugs may increase the adverse effects of vancomycin. Medicines that affect the kidneys, such as aminoglycosides, may increase the risk of kidney damage and should be avoided. In addition, coadministation of vancomycin and succinylcholine may result in a prolonged neuromuscular blockade. Patients should be monitored and a dose adjustment may be necessary. Vancomycin also has been reported to moderately interact with warfarin, potentially increasing the risk of bleeding. Patients who take warfarin should be closely monitored as they initiate and stop vancomycin therapy.
Vancomycin is pregnancy category C.