Early authors suggested peak levels of 30 to 40 mg/L and trough levels of 5 to 10 mg/L,
but current recommendations are that peak levels need not be measured and that trough levels of 10 to 15 mg/L or 15 to 20 mg/L, depending on the nature of the infection and the specific needs of the patient, may be appropriate. Using measured vancomycin concentrations to calculate doses optimizes therapy in patients with augmented renal clearance. Biosynthesis
Vancomycin is made by the soil bacterium Amycolatopsis orientalis. Vancomycin biosynthesis occurs primarily via three nonribosomal protein syntheses (NRPSs) VpsA, VpsB, and VpsC. The enzymes determine the amino acid sequence during its assembly through its 7 modules. Before vancomycin is assembled through NRPS, the non-proteinogenic amino acids are first synthesized. L-tyrosine is modified to become the β-hydroxytyrosine (β-HT) and 4-hydroxyphenylglycine (4-Hpg) residues. 3,5 dihydroxyphenylglycine ring (3,5-DPG) is derived from acetate. Nonribosomal peptide synthesis occurs through distinct modules that can load and extend the protein by one amino acid per module through the amide bond formation at the contact sites of the activating domains. Each module typically consists of an adenylation (A) domain, a peptidyl carrier protein (PCP) domain, and a condensation (C) domain. In the A domain, the specific amino acid is activated by converting into an aminoacyl adenylate enzyme complex attached to a 4phosphopantetheine cofactor by thioesterification The complex is then transferred to the PCP domain with the expulsion of AMP. The PCP domain uses the attached 4-phosphopantethein prosthetic group to load the growing peptide chain and their precursors.
Intravenous vs oral administration
Vancomycin must be given intravenously (IV) for systemic therapy, since it is not absorbed from the intestine. It is a large hydrophilic molecule that partitions poorly across the gastrointestinal mucosa. Due to short half-life, it is often injected twice daily.The only approved indication for oral vancomycin therapy is in the treatment of pseudomembranous colitis, where it must be given orally to reach the site of infection in the colon. Following oral administration, the fecal concentration of vancomycin is around 500 µg/mL (sensitive strains of C. difficile have a mean inhibitory concentration of ≤2 µg/mL)
Inhaled vancomycin has also been used (off-label), via nebulizer, for treatment of various infections of the upper and lower respiratory tract. There is an ongoing debate as to whether vancomycin should be given through a central or peripheral line. According to a 2014 review, midline catheters are a safe option for administration. Vancomycin Flushing Reaction (aka "Red man syndrome")
Vancomycin is recommended to be administered in a dilute solution slowly, over at least 60 min (maximum rate of 10 mg/min for doses >500 mg) due to the high incidence of pain and thrombophlebitis and to avoid an infusion reaction known as vancomycin flushing reaction. This phenomenon has been often clinically referred to as "red man syndrome".