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DEAR DR. ROACH: I'm a relatively healthy 54-year-old male. My daily medications are 20 mg of lisinopril, 20 mg of atorvastatin, and 145 mg of fenofibrate. I also take a 500-mg dose of naproxen on an as-needed basis for various aches and pains from military-service-related conditions. My naproxen intake varies anywhere from 0-4 doses per week. I exercise regularly and stay hydrated as well.
Every six months, I see my primary care physician for a wellness check that includes a blood lipid panel. Over the past few visits, I noticed that my kidney function results indicated a "mild to moderate decrease in kidney function," according to the chart provided with the lab results. My doctor tells me that my results are fine and that I shouldn't worry about it. My question is, can my combined intake of fenofibrate and naproxen cause acute or, even worse, chronic kidney damage?
-- J.R.
ANSWER: There are several causes of a kidney injury, some of which are hard to identify. However, there are two points that are relevant to your situation and important to recognize:
The most important is naproxen. Naproxen is in the category of nonsteroidal anti-inflammatory drugs (NSAIDs), and all of these drugs have the risk of both acute and chronic kidney injury. Approximately 3% of people who are taking these drugs will develop kidney damage, including both acute and chronic. However, you're taking a modest dose, which reduces your risk. Most people with NSAID-induced kidney injuries have taken over 3,000 doses of the medication over a span of more than five years.
However, there's another possibility. Fenofibrate modestly increases blood creatinine levels, which are the most common way of monitoring kidney function, but it doesn't normally cause long-term damage. Lisinopril always increases blood creatinine levels, making it look as though the kidneys are damaged. However, this increase (up to about 25% or so) is expected.
Not only does this fail to harm the kidneys, lisinopril is associated with a marked decrease in kidney damage from many causes, especially kidney disease that's associated with high urine protein (such as diabetes). Still, a greater-than-expected increase in the creatinine level can signify poor blood flow to the kidneys, so physicians monitor blood levels after starting lisinopril and similar drugs.
The decision of whether to do a more extensive evaluation of the kidneys or hold off on naproxen and recheck your blood levels requires clinical judgment.