U.S. flag An official website of the United States government
  1. Home
  2. Drug Databases
  3. Drug Safety-related Labeling Changes

Drug Safety-related Labeling Changes (SrLC)

Get Email Alerts | Guide

RIOMET ER (NDA-212595)

(METFORMIN HYDROCHLORIDE)

Safety-related Labeling Changes Approved by FDA Center for Drug Evaluation and Research (CDER)

Download Data

Expand all

08/11/2026 (SUPPL-2)

Approved Drug Label (PDF)

Boxed Warning

Additions and/or revisions underlined:

• Risk factors for metformin-associated lactic acidosis include renal impairment, concomitant use of certain drugs (e.g. carbonic anhydrase inhibitors such as topiramate), age 65 years old or greater, having a radiological study with contrast, surgery and other procedures, hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, hepatic impairment, and mitochondrial diseases [see Warnings and Precautions (5.1)].

5 Warnings and Precautions

5.1 Lactic Acidosis

Newly added information

      • Mitochondrial Diseases: Metformin may increase the risk of lactic acidosis in patients with mitochondrial diseases such as mitochondrial encephalomyopathy with lactic acidosis, and stroke-like episodes (MELAS) syndrome and maternally inherited diabetes and deafness (MIDD). RIOMET ER is not recommended in patients with mitochondrial diseases such as MELAS syndrome and MIDD.

        If a patient taking RIOMET ER develops elevated lactic acid levels (with or without accompanying neurologic signs and symptoms), discontinue RIOMET ER. Depending on the clinical context, consider evaluating the patient for MELAS, MIDD, or other mitochondrial disease.

17 PCI/PI/MG (Patient Counseling Information/Patient Information/Medication Guide)

PATIENT INFORMATION

Additions and/or revisions underlined:

RIOMET (ree oh met) ER (metformin hydrochloride

for extended-release oral suspension), for oral use

…

You have a higher chance for getting lactic acidosis if you:

…

  • have a genetically inherited disease affecting mitochondria (the energy-producing parts within cells) such as mitochondrial encephalomyopathy with lactic acidosis, and stroke-like episodes (MELAS) syndrome and maternally inherited diabetes and deafness (MIDD).

Before taking RIOMET ER, tell your healthcare provider about all of your medical conditions, including if you:

…

  • have a genetically inherited disease affecting mitochondria (the energy-producing parts within cells) such as MELAS syndrome or MIDD.

…