metformin and contrast dye

[AMwilldoit]

Hi! Just wanted to ask if a 500 mg tablet of Metformin given to a pt with normal renal function on a day that he got a CT scan with contrast is enough to cause lactic acidosis. Thanks!

[nurseprnRN, BSN, RN]

What's the classic cause of lactic acidosis?

Hint: It has nothing to do with kidneys.

(Well, normal kidneys will try to compensate by retaining bicarb, but lactic acidosis tends to come on quickly so the primary compensation would be hyperventilation to blow off CO2 (an acid).)

You are sure that it's LACTIC acidosis this patient had, and not some other acidosis? What do you think?

[AMwilldoit]

This question is specifically about the relationship between Metformin and contrast dyes. We were taught that Metformin should be withheld on the same day and delayed till 48 hours after a diagnostic test involving contrast dye. One of the potential serious complications listed is lactic acidosis if not withheld. Related literature had conflicting information regarding the condition of the renal system. Some say that risk for lactic acidosis in this situation will be present only for those with compromised kidney function. Others say that there is a risk regardless of kidney function. Just wanted to know if this particular dose (500 mg) combined with contrast dye can cause lactic acidosis in a patient with normal kidney function, based on your experiences. Patient does not currently have this diagnosis. Thanks!

[Esme12, ASN, BSN, RN]

The danger is in the patient that has preexisting kidney failure OR develops kidney failure after the administration of contrast medium AND the administration of Metformin continues. The actual policy varies per the facilities. I have worked at some that request it to be held for 48 prior and 48 hours post procedure although evidence doesn't support the pre-procedure holding of Metformin prior to the procedure has any clinical significance.

Intravascular administration of iodinated contrast media to patients who are receiving metformin, an oral antidiabetic agent, can result in lactic acidosis. However, this rare complication occurs only if the contrast medium causes renal failure, and the patient continues to take metformin in the presence of renal failure. Because metformin is excreted primarily by the kidneys, continued intake of metformin after the onset of renal failure results in a toxic accumulation of this drug and subsequent lactic acidosis. To avoid this complication, metformin must be withheld after the administration of the contrast agent for 48 hours, during which the contrast-induced renal failure becomes clinically apparent. If renal function is normal at 48 hours, the metformin can be restarted. There is no scientific justification for withholding metformin for 48 hours before administration of the contrast medium, as currently recommended in the package insert.

IV CONTRAST AND METFORMIN

Metformin and contrast media: where is th... [Can Assoc Radiol J. 1998] - PubMed - NCBI

Contrast Administration in Patients Receiving Metformin | UCSF Department of Radiology & Biomedical Imaging

Metformin Contraindications

Lactate uptake by the liver is diminished with metformin administration because lactate is a substrate for hepatic gluconeogenesis, a process that metformin inhibits. In healthy individuals, this slight excess is simply cleared by other mechanisms (including uptake by the kidneys, when their function is unimpaired), and no significant elevation in blood levels of lactate occurs.

When there is impaired renal function, however, clearance of metformin and lactate is reduced, leading to increased levels of both and possibly causing lactic acidosis due to a buildup of lactic acid. Because metformin decreases liver uptake of lactate, any condition that may precipitate lactic acidosis is a contraindication to its use.

Common causes of increased lactic acid production include alcoholism (due to depletion of NAD+ stores), heart failure, and respiratory disease (due to inadequate oxygenation of tissues); the most common cause of impaired lactic acid excretion is kidney disease.

[nurseprnRN, BSN, RN]

:) Much better answer.

[AMwilldoit]

Thank you so much for the reply and reference. Really appreciate it!

[Esme12, ASN, BSN, RN]

You are welcome...Google is your friend if you know what to look for.

I always back up the answers I know with good references...you need to read them and learn you'll remember it better