A 76-year-old patient with osteoarthritis is started on nabumetone (podcast) for chronic knee pain. A few weeks later, the patient reports that both legs and ankles are becoming swollen. The edema is attributed to “fluid retention,” and Lasix (furosemide) 20 mg daily is started.
The patient starts taking the Lasix and notices that the swelling improves. However, a routine laboratory panel a couple of weeks later shows that the serum creatinine has increased from 1.0 mg/dL to 1.6 mg/dL.
Nabumetone is an NSAID, and NSAIDs can cause sodium and fluid retention, which can contribute to peripheral edema (excellent board exam nugget). Instead of recognizing the edema as a potential adverse effect of the NSAID, a diuretic was added to treat the consequence of the original medication.
Now there is another problem. NSAIDs can reduce prostaglandin-mediated dilation of the afferent arteriole, decreasing renal blood flow. Furosemide can contribute to volume depletion and dehydration, particularly when the patient doesn’t have a strong indication for the diuretic or isn’t maintaining adequate fluid intake. The combination can put additional stress on kidney perfusion and contribute to an increase in serum creatinine or acute kidney injury.
This is a good example of why adding a medication for a new symptom isn’t always the best first step. The edema wasn’t necessarily a new disease that required another medication. It was likely an adverse effect of nabumetone. Nabumetone should have been reduced or changed to an alternative agent. The Lasix prescription could have been avoided, and the rise in creatinine would likely have been avoided as well.
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