THURSDAY, Sept. 13, 2018 (HealthDay News) -- People who took recalled blood pressure drugs containing a carcinogen do not appear to have a markedly increased short-term risk of cancer, a new study reports.
Doctors are reluctant to say they're fully in the clear, however.
The U.S. Food and Drug Administration in July recalled valsartan medicines manufactured by the Chinese company Zhejiang Huahai Pharmaceuticals.
The FDA and European health agencies took this step after learning that these products could have been contaminated with N-nitrosodimethylamine (NDMA), which is believed to cause cancer.
But Danish patients exposed to NDMA in valsartan products do not appear to be more likely to develop cancer, according to the study. It was published Sept. 13 in the BMJ.
"We found no evidence of an increase in short-term risk of cancer from exposure to NDMA-contaminated valsartan products in this study of all adult valsartan users in Denmark," said co-researcher Dr. Kasper Kristensen. He's a doctoral student with the University of Southern Denmark's public health department.
However, it's too soon to tell whether people exposed to NDMA through valsartan have a long-term higher risk of cancer, Kristensen added.
In addition, researchers did find some evidence that valsartan might influence short-term risk of colon and uterine cancer, although the results were not statistically significant.
One U.S. expert not involved with the study expressed caution.
"I don't think there's any reason to say this research sounds the all-clear," said Dr. James Januzzi, a cardiologist with Massachusetts General Hospital and member-elect of the American College of Cardiology Board of Trustees.
"I literally just got off the phone with a patient who called me about this question and I switched them off of generic valsartan to another drug," Januzzi said. "It's very much on everyone's mind."
Not all valsartan medicines for high blood pressure or heart failure have been recalled, only certain brands, the FDA says.
The recalled products include valsartan distributed by Major Pharmaceuticals, Solco Healthcare and Teva Pharmaceuticals Industries Ltd. They also include valsartan/hydrochlorothiazide formulations distributed by Solco Healthcare and Teva.
"The attributable cancer risk with NDMA contamination of generic valsartan seems to be very small, and certainly the research would support that fact," Januzzi said. "But to the extent this is a well-known carcinogen that is found in unacceptably high concentrations within the generic preparations in question, one should not discount the potential risk."
No one's exactly sure how NDMA wound up in valsartan, said Dr. Guy Mintz, director of cardiovascular health at North Shore University Hospital in Manhasset, N.Y.
"We don't know if it's a side product or byproduct of the reaction of creating valsartan medication, or some other form of contamination that hasn't quite been identified," Mintz said.
To see whether valsartan users are at increased risk, researchers identified 5,150 Danish patients with no history of cancer who took valsartan products between January 2012 and June 2018.
The researchers used prescription records to sort patients into two groups: those never exposed to NDMA and those probably or possibly prescribed valsartan products laced with NDMA.
The patients then were tracked for an average 4.6 years.
People prescribed valsartan containing NDMA did not have an overall increased risk of cancer, and there was no evidence that risk increased with the amount taken, researchers reported.
"Our results are in general reassuring," Kristensen said. "However, we cannot positively exclude a modest increase in cancer risk and have no information on late cancer risk. Hence, it is too early to state that the NDMA contamination has not posed a significant risk."
Dr. Satjit Bhusri, a cardiologist with Lenox Hill Hospital in New York City, agreed.
"This study may give some reassurance to people already exposed to this additive, but this should not prevent patients from routine cancer screening and future avoidance of this additive," Bhusri said.
Mintz said he too has had patients ask to be taken off valsartan and put on another blood pressure drug.
"I'll explain there's no recall with regard to other products in the valsartan family and tell them I think this is a very well-tolerated drug," he said.
Mintz added that it's critical patients not stop taking blood pressure or heart failure drugs containing valsartan without first speaking with their physician.
"The last thing you want is to have a patient with a weak heart muscle to stop their medication," Mintz said. "The work of the heart increases and you can precipitate heart failure. Make an appointment and see your doctor. We have many different alternatives there for you."
The American Heart Association has more about blood pressure medications.