The prescribing information for metformin ER tablets, including the patient information leaflet printed in it, makes specific statements about kidney function, iodinated contrast imaging, surgery, alcohol and hepatic impairment. This guide reports those statements. They are label wording, not advice for any person, and a licensed provider decides what applies. The sections below take kidney function, contrast imaging and surgery, alcohol and hepatic impairment, and infection and fluid loss in turn.
Kidney function and eGFR
The label states numbers for eGFR in several places. The table gives them as the label words them.
| Question | What the source says |
|---|---|
| When are the tablets contraindicated? | The label's warnings section states that the tablets are contraindicated in patients with an eGFR less than 30. |
| What about starting the tablets? | The label's warnings section states that initiation is not recommended in patients with eGFR between 30 to 45. |
| What if eGFR falls? | The label's highlights say to assess risk/benefit of continuing if eGFR falls below 45. |
| How often is eGFR obtained? | The label's warnings section says to obtain an eGFR at least annually in all patients taking the tablets. |
The contraindications section also lists hypersensitivity to metformin and acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma. The patient information leaflet lists kidney problems among the things that give you a higher chance of getting lactic acidosis, and says people whose kidneys are not working properly should not take the tablets.
Contrast imaging, surgery and other procedures
For contrast imaging, the warnings section says to stop the tablets at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60. The label also says to re-evaluate eGFR 48 hours after the imaging procedure, and restart the tablets if renal function is stable. The patient information leaflet says that if you are going to get an injection of dye or contrast agents for an x-ray procedure, or are going to have surgery and not able to eat or drink much, the tablets will need to be stopped for a short time. It also says to talk to your healthcare provider about when you should stop the tablets and when you should start them again. The sections word this differently.
For surgery and other procedures, the warnings section states that withholding of food and fluids during surgical or other procedures may increase the risk for volume depletion, hypotension, and renal impairment. It says the tablets should be temporarily discontinued while patients have restricted food and fluid intake. The patient counseling section says to instruct patients to inform their doctor that they are taking the tablets prior to any surgical or radiological procedure, as temporary discontinuation may be required. The warnings statement concerns food and fluid restriction, and the counseling statement concerns telling the doctor.
Alcohol and hepatic impairment
The warnings section states that alcohol potentiates the effect of metformin on lactate metabolism and that patients should be warned against excessive alcohol intake while receiving the tablets.
The hepatic impairment subsection states that use of metformin in patients with hepatic impairment has been associated with some cases of lactic acidosis, and that the tablets are not recommended in patients with hepatic impairment.
Infection and fluid loss
The patient information leaflet says that when your body is under some types of stress, such as fever, trauma (such as a car accident), infection, or surgery, the amount of diabetes medicine that you need may change. It says to tell your healthcare provider right away if you have any of these problems.
The leaflet also describes getting dehydrated as losing a large amount of body fluids. It says this can happen if you are sick with a fever, vomiting, or diarrhea, and can also happen when you sweat a lot with activity or exercise and do not drink enough fluids.
What this does not tell you
These are statements from a label and the patient information printed in it. They do not say whether any statement applies to a particular person. The eGFR numbers are shown as the label's quoted passages give them, without units. The label's contrast statement is worded for patients with an eGFR between 30 and 60, and it does not say what applies in other situations. The quoted passages do not define how much alcohol is excessive. This guide does not cover the boxed warning wording, drug interactions or dosing. The leaflet says to tell a healthcare provider right away about stress such as fever or infection, and the counseling section says to tell the doctor about the tablets before any surgical or radiological procedure. A licensed provider reviews those details and decides.