April 30, 2017
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(metformin hydrochloride) Oral Solution



  • Lactic acidosis is a rare but serious complication that can occur due to metformin accumulation. The risk increases with conditions such as sepsis, dehydration, excess alcohol intake, hepatic impairment, renal impairment, and acute congestive heart failure [see WARNINGS AND PRECAUTIONS].
  • The onset is often subtle accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, increasing somnolence, and nonspecific abdominal distress. Laboratory abnormalities include low pH, increased anion gap, and elevated blood lactate [see WARNINGS AND PRECAUTIONS].
  • If acidosis is suspected Riomet should be discontinued and the patient hospitalized immediately [see WARNINGS AND PRECAUTIONS].


Riomet (metformin hydrochloride oral solution) is an oral antihyperglycemic drug used in the management of type 2 diabetes. Metformin hydrochloride, USP (N,N­dimethylimidodicarbonimidic diamide hydrochloride) is not chemically or pharmacologically related to any other classes of oral antihyperglycemic agents. The structural formula is as shown:

RIOMET® (metformin hydrochloride) Structural Formula Illustration

Metformin hydrochloride, USP is a white crystalline powder with a molecular formula of C4H11N5•HCl and a molecular weight of 165.62. Metformin hydrochloride, USP 2.0 g is soluble in 20 mL of water. The pKa of metformin is 12.4. The pH of a 1% aqueous solution of metformin hydrochloride is 6.68. It is freely soluble in water; slightly soluble in alcohol; practically insoluble in acetone and in methylene chloride.

Riomet (Cherry Flavor) contains 500 mg of metformin hydrochloride, USP per 5 mL and the following inactive ingredients: Artificial cherry flavor, hydrochloric acid, potassium bicarbonate, purified water, saccharin calcium, and xylitol.

Riomet (Strawberry Flavor) contains 500 mg of metformin hydrochloride, USP per 5 mL and the following inactive ingredients: Hydrochloric acid, N&A strawberry flavor (propylene glycol and glycerin), potassium bicarbonate, purified water, sucralose, and xylitol.

What are the possible side effects of metformin (Fortamet, Glucophage, Glucophage XR, Glumetza, Riomet)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

This medication may cause lactic acidosis (a build-up of lactic acid in the body, which can be fatal). Lactic acidosis can start slowly and get worse over time. Get emergency medical help if you have even mild symptoms of lactic acidosis, such as:

  • muscle pain or weakness;
  • numb or cold feeling in your arms and legs;
  • trouble...

Read All Potential Side Effects and See Pictures of Riomet »

What are the precautions when taking metformin hcl (Riomet)?

See also Warning section.

Before taking this medication, tell your doctor or pharmacist if you are allergic to metformin; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: severe breathing problems (such as obstructive lung disease, severe asthma), blood problems (such as anemia, vitamin B12 deficiency), kidney disease, liver disease.

Before having surgery or any X-ray/scanning procedure using injectable iodinated contrast material, tell your doctor that you are taking this medication. You will need to temporarily stop this medication before...

Read All Potential Precautions of Riomet »

Last reviewed on RxList: 3/7/2017
This monograph has been modified to include the generic and brand name in many instances.

Riomet - User Reviews

Riomet User Reviews

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