From the Guidelines
Metronidazole does not typically increase blood urea nitrogen (BUN) or serum creatinine levels in patients with normal kidney function. This is because the drug is primarily metabolized by the liver and does not directly impact kidney function in most patients 1. The guidelines for the treatment of Clostridioides difficile infection (CDI) recommend metronidazole as a first-line treatment option, with a dosage of 500 mg tid PO for 10 days, without mentioning any concerns about increased BUN or serum creatinine levels 1. However, it is worth noting that patients with pre-existing kidney disease may require dose adjustments, as metronidazole can accumulate in these patients. Additionally, while rare, there have been isolated case reports of acute kidney injury associated with metronidazole use, but this is not considered a common or expected side effect. Key points to consider include:
- Metronidazole is primarily metabolized by the liver, with approximately 60-80% of the drug metabolized hepatically and only about 20% excreted unchanged in urine 1.
- The medication's clearance is minimally affected by kidney function, which explains why it generally doesn't impact BUN and creatinine levels 1.
- Routine monitoring of BUN and creatinine is not typically required for metronidazole unless the patient has underlying kidney disease 1.
From the FDA Drug Label
Serum lithium and serum creatinine levels should be obtained several days after beginning metronidazole to detect any increase that may precede clinical symptoms of lithium intoxication.
The FDA drug label does not directly answer the question of whether metronidazole increases blood urea nitrogen (BUN) levels. However, it mentions that serum creatinine levels should be monitored, implying a potential impact on renal function.
- Key points:
- The label does not provide direct information on the effect of metronidazole on BUN levels.
- It suggests monitoring serum creatinine levels, which may indicate a potential effect on renal function.
- No conclusion can be drawn about the effect of metronidazole on BUN levels based on the provided information 2.
From the Research
Metronidazole and Kidney Function
- The provided studies do not directly address the effect of metronidazole on blood urea nitrogen (BUN) and serum creatinine levels 3, 4, 5.
- However, the studies discuss the importance of BUN and serum creatinine as markers of kidney function, and how they can be influenced by various renal and non-renal factors 4, 5.
- It is mentioned that elevations in BUN and serum creatinine levels do not necessarily indicate structural renal disease, and that normal levels do not rule out significant reduction in glomerular filtration rate 5.
- The studies also highlight the importance of considering the BUN to creatinine ratio and other biomarkers, such as urine albumin and kidney injury molecule-1 (KIM-1), in assessing kidney function and detecting drug-induced kidney toxicity 3, 4.
Biomarkers of Kidney Function
- The use of biomarkers, such as urine albumin, urine protein, and KIM-1, can provide a more accurate assessment of kidney function and detect early signs of kidney damage 3.
- These biomarkers can be used in conjunction with BUN and serum creatinine levels to provide a more comprehensive understanding of kidney function 3, 4.
- The studies suggest that a combined use of functional and damage markers may advance the field of biomarkers of drug-induced kidney toxicity 3.