What is the appropriate vancomycin dose and interval for a 68-year-old patient weighing 63 kg with a serum creatinine of 0.72 mg/dL?

Vancomycin Dosing for 68-Year-Old Patient

For this 68-year-old patient weighing 63 kg with excellent renal function (SCr 0.72 mg/dL, estimated CrCl ~90-100 mL/min), initiate vancomycin at 1000 mg IV every 12 hours, infused over at least 60 minutes per dose. 1, 2, 3

Dosing Rationale

Weight-Based Calculation

• Standard dosing is 15-20 mg/kg actual body weight every 8-12 hours for adults with normal renal function 1, 2
• For this 63 kg patient: 15 mg/kg × 63 kg = 945 mg per dose, which rounds to 1000 mg 1, 3
• The FDA label confirms that 1 g every 12 hours is appropriate for adults with normal renal function 3
• This patient's excellent renal function (SCr 0.72) supports a 12-hour interval rather than 8-hour dosing 1, 2

Loading Dose Consideration

• A loading dose of 25-30 mg/kg is NOT necessary unless the patient has sepsis, bacteremia, endocarditis, meningitis, pneumonia, or other serious MRSA infection 1, 2
• If a loading dose is indicated: 25 mg/kg × 63 kg = 1575 mg (round to 1500-1750 mg), infused over 2 hours 1, 2
• The loading dose should be given regardless of renal function, as it fills the volume of distribution 2

Infusion Guidelines

Administration Rate

• Each 1000 mg dose must be infused over at least 60 minutes to minimize red man syndrome risk 1, 3
• The FDA label specifies a maximum rate of 10 mg/min, which for 1000 mg equals 100 minutes minimum 3
• For doses >1 gram, extend infusion to 1.5-2 hours 1

Concentration

• Reconstitute to 50 mg/mL, then dilute each 1000 mg dose in at least 200 mL of compatible solution (5% dextrose or 0.9% sodium chloride) 3
• Final concentration should not exceed 5 mg/mL (10 mg/mL maximum in fluid-restricted patients) 3

Therapeutic Monitoring

Trough Timing

• Obtain first trough level immediately before the 4th dose (at steady state, approximately 48-60 hours after initiation) 1, 4
• Draw within 30 minutes before the next scheduled dose 4

Target Trough Concentrations

• For serious infections (bacteremia, endocarditis, osteomyelitis, meningitis, pneumonia): 15-20 mg/L 1, 2, 4
• For non-severe infections (uncomplicated skin/soft tissue): 10-15 mg/L 1, 2
• Trough >20 mg/L significantly increases nephrotoxicity risk and requires immediate dose hold 1, 4

Monitoring Frequency

• Check serum creatinine at least twice weekly throughout therapy 4
• Recheck trough with each dose adjustment 4
• For stable patients on prolonged therapy, recheck trough weekly 4

Critical Pitfalls to Avoid

Common Dosing Errors

• Never use fixed 1 g every 12 hours without weight-based calculation - this approach fails to account for patient-specific factors 1, 2
• Never reduce or omit loading dose based on renal function in seriously ill patients - this delays therapeutic concentrations 2
• Never target 15-20 mg/L troughs for non-severe infections - this unnecessarily increases nephrotoxicity risk 1, 2

Monitoring Errors

• Never monitor peak levels - they provide no clinical value and trough-only monitoring is the standard 4
• Never draw trough before the 4th dose - steady state has not been achieved 4
• Never continue same dose when trough >20 mg/L - hold dose immediately and recheck before resuming 4

MIC Considerations

• If vancomycin MIC ≥2 μg/mL, switch to alternative agent (daptomycin, linezolid, or ceftaroline) as target AUC/MIC >400 is not achievable 1, 2, 4

Renal Function Monitoring

• This patient's estimated CrCl is approximately 90-100 mL/min based on age 68, weight 63 kg, and SCr 0.72 mg/dL 3
• Using Cockcroft-Gault: [(140-68) × 63] / (72 × 0.72) = 88 mL/min for males (multiply by 0.85 for females = 75 mL/min) 3
• Monitor for nephrotoxicity, especially if concurrent nephrotoxic agents (aminoglycosides, piperacillin-tazobactam, NSAIDs, contrast) 1, 2