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Side Effects of


Home>Side Effects>Biguanides

Description: Biguanides are a chemical class whose derivatives are used in the treatment diabetes mellitus and as antimalarials. Adverse reactions are similar across all medications within this class. (Japanese Journal of Clinical Medicine “Adverse effects of biguanides,” Sep 2002). Examples of drugs in this class include:

  • Metformin (Glucophage)
  • Phenformin
  • Buformin
  • Proguanil
  • Chlorproguanil

Common Side Effects

Metformin (brand name Glucophage) is used in the treatment of diabetes mellitus. It acts as an antihyperglycemic drug and is associated with a number of side effects. These include, according to the Glucophage label as reported by the U.S. Food and Drug Administration (FDA):

  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Loss of appetite
  • Hypoglycemia (low blood glucose concentration)
  • Flatulence (excessive gas)
  • Indigestion
  • Chills
  • Flu-like syndrome
  • Hepatitis (inflammation of the liver)
  • Flushing
  • Palpitations
  • Rash
  • Hyperhidrosis (increased amounts of sweating)
  • Infections
  • Myalgia (muscle pains)
  • Lightheadedness
  • Headaches

Proguanil (malarone) also known as chlorguanide and chloroguanide, is a medication used to treat and prevent malaria. Side effects include:

  • Pruritus
  • Nausea
  • Vomiting
  • Diarrhea
  • Mouth ulcers
  • Anorexia
  • Dyspepsia (indigestion)
  • Myalgia
  • Back pain

(Glaxo Smith Kline monograph on Malarone)

Understand Your Risk for Side Effects with the Rxight® Genetic Test

Some patients may react adversely to the medication while others don’t suffer. This interpatient variability is in part explained by inter-individual variation in the metabolism of medications. Pharmacogenetics refers to science of the variability in the genomes of different patients and how this can affect the efficacy of medications. Polymorphisms (individual variants) in genes that interact with drugs like metformin can increase the probability of developing side effects when taking those medications. The Rxight® test specifically evaluates genes and their alleles to determine how well you process hundreds of medications across over 50 pharmacological classes, including biguanides. The detailed results – which flag medications that could be problematic in either producing side effects or not being effective at standard doses – can then guide your prescriber in finding the right dose or an alternative and safer medication, tailored to your unique genotype.

Contributors to this Article:
Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry

Biguanides Tested Include:

Read more about Rxight® Drug Sensitivity Testing