Is a BUN of 30 okay for ordering 500 mg of Levaquin (levofloxacin)?

Levofloxacin Dosing with Elevated BUN of 30

A BUN of 30 requires dosage adjustment for levofloxacin 500 mg, as this level indicates renal impairment that affects drug clearance. 1

Assessment of Renal Function

When considering levofloxacin administration with an elevated BUN of 30, it's critical to evaluate the patient's renal function more precisely:

• BUN of 30 mg/dL suggests impaired renal function, but creatinine clearance (CrCl) is the key parameter for dosing decisions
• The FDA label specifically states: "For patients with creatinine clearance < 50 mL/min, adjustment of the dosage regimen is necessary to avoid the accumulation of levofloxacin due to decreased clearance" 1

Recommended Dosage Adjustments

Based on the patient's likely impaired renal function:

1. Calculate creatinine clearance using the Cockcroft-Gault equation (requires serum creatinine, age, weight, and gender)

2. Adjust dosing according to CrCl:

   • If CrCl ≥ 50 mL/min: Standard dose of 500 mg daily
   • If CrCl 20-49 mL/min: 500 mg initially, then 250 mg every 24 hours
   • If CrCl 10-19 mL/min: 500 mg initially, then 250 mg every 48 hours
   • If CrCl < 10 mL/min: 500 mg initially, then 250 mg every 48 hours 2, 1

Important Clinical Considerations

• Levofloxacin elimination is primarily renal - approximately 80% is eliminated unchanged in urine through glomerular filtration and tubular secretion 3
• Accumulation risk - without dose adjustment, levofloxacin can accumulate in patients with renal impairment, potentially increasing toxicity 1
• Monitoring - careful clinical observation and appropriate laboratory studies should be performed prior to and during therapy 1
• Hydration - adequate hydration should be maintained to prevent the formation of highly concentrated urine and crystalluria 1

Administration Guidelines

• Administer levofloxacin at least two hours before or two hours after antacids containing magnesium or aluminum, sucralfate, metal cations like iron, and multivitamin preparations with zinc 1
• Levofloxacin can be administered without regard to food 1

Common Pitfalls to Avoid

1. Relying solely on BUN - BUN alone is insufficient for dosing decisions; creatinine clearance is the critical parameter
2. Failure to give loading dose - even with renal impairment, an initial full dose is recommended to achieve therapeutic levels quickly
3. Inadequate hydration - fluoroquinolones require adequate hydration to prevent crystalluria
4. Drug interactions - concurrent administration with divalent cations significantly decreases levofloxacin absorption 3

Remember that appropriate dosing of levofloxacin in renal impairment is essential to maintain efficacy while minimizing toxicity risks.