To what dose should a calculated 625 mg intravenous vancomycin be rounded?

Vancomycin Dose Rounding for 625 mg IV

Round 625 mg of IV vancomycin to 500 mg or 750 mg depending on the clinical context, with 500 mg being appropriate for non-severe infections and 750 mg (or higher) for serious infections requiring weight-based dosing of 15-20 mg/kg.

Rounding Algorithm Based on Clinical Context

For Non-Severe Infections

• Round down to 500 mg if the calculated dose of 625 mg represents a patient with a non-severe infection (e.g., uncomplicated skin/soft tissue infection) where traditional dosing of 1 g every 12 hours (500 mg every 6 hours) is adequate. 1
• This approach is supported for patients with normal renal function who are not obese and have non-severe infections. 2

For Serious Infections Requiring Weight-Based Dosing

• Round up to 750 mg if the 625 mg dose was calculated using 15-20 mg/kg for a serious infection (e.g., bacteremia, endocarditis, osteomyelitis, meningitis, pneumonia, necrotizing fasciitis). 1, 2
• Weight-based dosing of 15-20 mg/kg every 8-12 hours is the standard for serious MRSA infections, with a maximum single dose of 2 g. 2, 3
• Rounding to the nearest 250 mg increment (500 mg, 750 mg, 1000 mg, etc.) is standard practice to align with available vial sizes and minimize waste. 3

Key Dosing Principles

Standard Adult Dosing Framework

• The FDA label recommends 500 mg every 6 hours or 1 g every 12 hours (total 2 g/day) for adults with normal renal function. 3
• For serious infections, guidelines recommend 15-20 mg/kg/dose every 8-12 hours, not exceeding 2 g per dose. 1, 2
• Each dose should be administered over at least 60 minutes or at no more than 10 mg/min, whichever is longer. 3

Therapeutic Targets

• Target trough concentrations of 10-15 μg/mL for non-severe infections and 15-20 μg/mL for serious infections. 1, 2, 4
• The pharmacodynamic target is an AUC/MIC ratio >400, which correlates with clinical efficacy. 2

Common Pitfalls to Avoid

• Do not use fixed 1-gram doses in obese patients or those with serious infections, as this frequently results in subtherapeutic levels, especially in patients weighing >70 kg. 2
• Avoid rounding down excessively in serious infections, as underdosing can lead to treatment failure and promote resistance development. 2
• Consider the patient's actual body weight when calculating doses, not ideal body weight, particularly in obese patients. 2
• If the vancomycin MIC is ≥2 μg/mL, switch to an alternative agent (daptomycin, linezolid, ceftaroline) as target AUC/MIC ratios may not be achievable. 2, 4

Practical Rounding Guidance

• Rounding to the nearest 250 mg (500 mg, 750 mg, 1000 mg) aligns with standard vial sizes and infusion preparation. 3
• For a calculated dose of 625 mg in a serious infection requiring aggressive therapy, rounding up to 750 mg is more appropriate than rounding down to 500 mg. 2
• For non-severe infections where 625 mg was calculated, rounding down to 500 mg every 6 hours (or 1 g every 12 hours) is acceptable. 1, 3