Unit Converter
Vancomycin
(Glycopeptide Antibiotic - Requires AUC-Based Therapeutic Drug Monitoring to Prevent Nephrotoxicity)
Synonyms
- Vancomycin
- Vanc
- Glycopeptide antibiotic
- Intravenous vancomycin
- “Vanco” (informal)
- TDM for vancomycin
Units of Measurement
- µmol/L
- mg/L
- mg/dL
- mg/100 mL
- mg%
- µg/mL
Unit Conversions
Molecular Weight of Vancomycin = ~1449 g/mol
µmol/L → mg/L
1 µmol/L=1.449 mg/L1\ \text{µmol/L} = 1.449\ \text{mg/L}1 µmol/L=1.449 mg/L 1 mg/L=0.69 µmol/L1\ \text{mg/L} = 0.69\ \text{µmol/L}1 mg/L=0.69 µmol/L
mg/dL = mg/100 mL = mg%
1 mg/dL=10 mg/L1\ \text{mg/dL} = 10\ \text{mg/L}1 mg/dL=10 mg/L
µg/mL → mg/L
1 µg/mL=1 mg/L1\ \text{µg/mL} = 1\ \text{mg/L}1 µg/mL=1 mg/L
Description
Vancomycin is a glycopeptide antibiotic used to treat serious Gram-positive infections, especially:
- MRSA
- Enterococcus (if susceptible)
- Staphylococcus epidermidis
- Clostridium difficile (oral form only)
It inhibits cell wall synthesis by binding D-Ala-D-Ala terminals of peptidoglycan precursors.
Why Monitoring is Required
- Narrow therapeutic window
- Risk of nephrotoxicity ↑ with high levels
- Subtherapeutic levels → resistance & treatment failure
- AUC/MIC ratio is the pharmacodynamic goal
Pharmacology
- IV vancomycin is required for systemic infections
- Oral vancomycin stays in GI tract (only for C. difficile)
- Primarily eliminated by kidneys – GFR strongly influences dosing
- Half-life prolonged in renal impairment
- Poor tissue penetration compared to beta-lactams
Clinical Significance
ELEVATED LEVELS
Major Toxicities
- Nephrotoxicity (most important)
- Ototoxicity
- Red Man Syndrome (histamine release from rapid infusion)
- Neutropenia (rare)
High troughs (>20 mg/L) are associated with AKI.
LOW LEVELS
→ Risk of treatment failure, persistent MRSA bacteremia, resistance.
Seen in:
- Inadequate dosing
- High clearance states
- Obesity
- Burns
- Pregnancy
- Augmented renal clearance (ARC) in ICU patients
AUC-BASED TARGETS
Preferred Parameter
AUC24/MIC target=400–600\textbf{AUC}_{24}/\text{MIC target} = 400–600AUC24/MIC target=400–600
Trough-only monitoring is outdated, but still referenced where AUC not available.
Reference Intervals
(Useful when AUC monitoring unavailable)
Trough (pre-dose) Levels
| Clinical Situation | Target Trough |
| Uncomplicated skin/soft tissue | 10–15 mg/L |
| MRSA bacteremia | 15–20 mg/L |
| Pneumonia | 15–20 mg/L |
| Osteomyelitis | 15–20 mg/L |
| Endocarditis | 15–20 mg/L |
| CNS infections | 15–20 mg/L |
Toxic trough level: >20 mg/L
Peak levels are NOT routinely recommended
Diagnostic Uses
1. TDM in Serious Gram-Positive Infections
Ensures adequate exposure.
2. Adjusting Dosing in Renal Dysfunction
Dosing intervals change with declining GFR.
3. Preventing Nephrotoxicity
Avoid sustained levels >20 mg/L.
4. Monitoring in High-Risk Populations
- ICU patients
- Elderly
- Obese
- Pediatrics
- Dialysis patients
5. AUC-Based Dosing
Preferred in modern practice using Bayesian software or paired peak–trough.
Analytical Notes
- Timing is CRUCIAL:
- Trough: draw 30 minutes before next dose
- Trough: draw 30 minutes before next dose
- Avoid drawing during infusion
- Hemodialysis removes vancomycin inconsistently
- Measured by immunoassay or LC-MS/MS
Clinical Pearls
- Red Man Syndrome is NOT an allergy - slow infusion + antihistamine.
- For obese patients, dosing is based on actual body weight.
- Oral vancomycin does NOT require monitoring (not absorbed).
- High creatinine clearance (>130 mL/min) can cause subtherapeutic levels.
- Concomitant nephrotoxins (aminoglycosides, piperacillin-tazobactam) ↑ AKI risk.
Interesting Fact
Vancomycin was called “Mississippi Mud” when first developed because early formulations were brown and impure - modern purification has eliminated this issue.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - TDM
- IDSA/ASHP Vancomycin Monitoring Guidelines 2020
- ACCP Infectious Disease Pharmacotherapy
- Mayo Clinic Laboratories - Vancomycin Level
- ARUP Consult - Therapeutic Drug Monitoring
- NIH/MedlinePlus - Vancomycin Test