So the FDA changed the labeling on metformin a while back and made it a little easier to use the drug in more patients who have poor kidney function.  Whenever changes like this happen, I like to take a little time and digest the changes.

From a recent Medscape article, here’s what one physician, Dr Inzucch, interpreted, “What the guidelines now state is that, essentially, the drug may be used when the eGFR is between 45 and 60 mL/min per 1.73 m² — ie, mild chronic kidney disease (CKD). When the eGFR falls to between 30 and 45, which is moderate CKD, the FDA appropriately recommends further caution with a careful risk/benefit calculation before deciding to stop or continue the medication.”

So what patients am I going to look at in regards to potentially starting or changing metformin?  The new guidance is less restrictive, so in theory, we will likely see more patients on metformin going forward.  Here’s a few things I’ve thought about, assuming their kidney function falls within the new ranges.

• Patients who’ve been on numerous oral diabetes medications and whose kidney function was previously borderline might be good candidates for restart.
• Consider in patients who are on very expensive diabetes medications with borderline kidney function.
• Start low, go slow and possibly avoid max doses in those patients that have borderline kidney function.
• Consider in those with significant weight gain from other diabetes medications (i.e. sulfonylureas).
• I’ve seen situations where patients have had acute renal failure due to a UTI or other resolvable issue.  If kidney function is back to an acceptable range, consideration could be given to starting or restarting metformin.

I’ve had a couple of patients so far that I have recommended to relook at metformin as an option.

What other situations have you seen that might warrant starting or potentially restarting metformin in patients with kidney disease?

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