01:10 - Source: CNN
Trouble sleeping? This may be why
Now playing
01:10
Trouble sleeping? This may be why
Woman pointing to area on mammogram x-ray, close-up
Getty Images/File
Woman pointing to area on mammogram x-ray, close-up
Now playing
01:19
Breast cancer: Know the facts
Laboratory Fertilization Of Eggs In IVF Treatment  Stock Photo:Image ID: 155727377
Shutterstock
Laboratory Fertilization Of Eggs In IVF Treatment Stock Photo:Image ID: 155727377
Now playing
03:06
Explain it to me: Fertility
Ways to treat heartburn_00000026.jpg
Ways to treat heartburn_00000026.jpg
Now playing
02:40
Ways to treat heartburn
CNN
Now playing
02:13
Why losing weight might protect you from Covid-19
this is your brain on pain health orig_00001025.jpg
CNN
this is your brain on pain health orig_00001025.jpg
Now playing
01:39
This is your brain on pain
Now playing
01:42
Here's why you can't stop eating pizza, ice cream and chocolate chip cookies
shutterstock
Now playing
01:49
These foods aren't as healthy as you think
Americans are still too fat according to a new study from JAMA. Two in three of Americans are registering as overweight or obese.
Shutterstock
Americans are still too fat according to a new study from JAMA. Two in three of Americans are registering as overweight or obese.
Now playing
01:15
What is obesity?
CNN
Now playing
01:17
Why your BMI matters
LONDON - MAY 16:  In this photo illustration a cigarette is seen burning on May 16, 2007 in London. Businesses and shops are gearing up for the introduction of the smoking ban on July 1 in England after similar bans have been introduced in Ireland, Scotland and Wales.  (Photo Illustration by Bruno Vincent/Getty Images)
Bruno Vincent/Getty Images Europe/Getty Images
LONDON - MAY 16: In this photo illustration a cigarette is seen burning on May 16, 2007 in London. Businesses and shops are gearing up for the introduction of the smoking ban on July 1 in England after similar bans have been introduced in Ireland, Scotland and Wales. (Photo Illustration by Bruno Vincent/Getty Images)
Now playing
01:07
What tobacco does to your health (2017)
Photo Illustration/Thinkstock
Now playing
01:12
World blood pressure rises (2016)
A surgeon sitting in front of screens of a Focal One device performs a robot-assisted prostate tumorectomy using ultrasound imaging on April 10, 2014 at the Edouard Herriot hospital in Lyon, center France. Focal One is the first robotic HIFU (high intensity focused ultrasound) device dedicated to the focal approach for prostate cancer therapy. According to EDAP TMS SA, a leader in therapeutic ultrasound, it combines the three essential components to efficiently perform a focal treatment: state-of-the-art imaging to localized tumors with the use of magnetic resonance imaging (MRI) combined with real-time ultrasound, utmost precision of robotic HIFU treatment focused only on identified targeted cancer areas, and immediate feedback on treatment efficacy utilizing Contrast-Enhanced Ultrasound Imaging. AFP PHOTO / JEFF PACHOUD        (Photo credit should read JEFF PACHOUD/AFP/Getty Images)
JEFF PACHOUD/AFP/AFP/Getty Images
A surgeon sitting in front of screens of a Focal One device performs a robot-assisted prostate tumorectomy using ultrasound imaging on April 10, 2014 at the Edouard Herriot hospital in Lyon, center France. Focal One is the first robotic HIFU (high intensity focused ultrasound) device dedicated to the focal approach for prostate cancer therapy. According to EDAP TMS SA, a leader in therapeutic ultrasound, it combines the three essential components to efficiently perform a focal treatment: state-of-the-art imaging to localized tumors with the use of magnetic resonance imaging (MRI) combined with real-time ultrasound, utmost precision of robotic HIFU treatment focused only on identified targeted cancer areas, and immediate feedback on treatment efficacy utilizing Contrast-Enhanced Ultrasound Imaging. AFP PHOTO / JEFF PACHOUD (Photo credit should read JEFF PACHOUD/AFP/Getty Images)
Now playing
01:21
What is prostate cancer?
Argosy
Now playing
00:53
What is Parkinson's disease?
Now playing
01:38
How Alzheimer's destroys the brain
(CNN) —  

Drugmaker Novartis said it is halting distribution of all ranitidine medicines made by Sandoz, a measure it called “precautionary” after the acid-reducing medications were found to contain an impurity.

The move comes after the US Food and Drug Administration and European Medicines Agency announced earlier this month that tests showed some ranitidine products contained NDMA, which is classified as a probable human carcinogen based on lab tests.

The FDA is evaluating whether the low levels of NDMA in ranitidine pose a risk to patients and said it will share the information when it is available.

Ranitidine is an over-the-counter and prescription histamine-2 blocker, which decreases the amount of stomach acid.

“A precautionary distribution stop of all Sandoz ranitidine-containing medicines in all our markets will remain in place under further clarification, this includes capsules in the USA. Our internal investigation is ongoing to determine further details. In case of concerns, adequate additional measures will be implemented in alignment with relevant Health Authorities as required,” Novartis said in a emailed statement.

Drugmaker Sanofi, which makes ranitidine medication sold under the brand name Zantac, said in a statement emailed on Thursday that it currently has “no plans to stop distributing or manufacturing Zantac or other ranitidine products outside of Canada.”

“The FDA reported that the levels of N-nitrosodimethylamine (NDMA) in ranitidine in preliminary tests barely exceed amounts found in common foods. We are working closely with the FDA and are conducting our own robust investigations to ensure we continue to meet the highest quality safety and quality standards,” Sanofi’s statement said.

The FDA has been investigating NDMA and other impurities in blood pressure and heart medicines known as ARBs since last year. Numerous recalls have been launched as the FDA found “unacceptable levels” of nitrosamines in those drugs.

The FDA says people don’t need to stop taking the ranitidine medication, but patients taking the prescription versions may want to talk to their doctors about other treatment options, and people taking the over-the-counter version can consider other medicines approved for their conditions.

Get CNN Health's weekly newsletter

Sign up here to get The Results Are In with Dr. Sanjay Gupta every Tuesday from the CNN Health team.

NDMA can cause harm in large amounts, but the levels the FDA found in preliminary tests of ranitidine “barely exceed amounts you might expect to find in common foods,” according to a statement last week from Dr. Janet Woodcock, research director for FDA’s Centers for Drug Evaluation and Research.

Woodcock said the agency is working with international regulators and industry partners to determine the source of the ranitidine impurity.

People can report adverse health reactions with ranitidine to the FDA’s MedWatch.