Tuberculosis Antibiotics Contain Potentially Cancer-Causing Impurities: FDA

Federal regulators indicate that the tuberculosis antibiotic drugs rifampin and rifapentine may have been distributed with nitrosamine impurities, which could increase the risk of cancer. However, patients taking the drugs are being advised to continue with the medication and consult their health care providers about any concerns.

In a press release issued on August 26, the FDA acknowledged that it become aware that manufacturers found 1-methyl-4-nitrosopiperazine (MNP) in some samples of rifampin, and 1-cyclopentyle-4-nitrosopiperazine (CPNP) in samples of rifapentine, which are above the acceptable intake limits.

Despite the potential presences of the cancer-causing impurities, the agency indicates that it will not object to the ongoing distribution of these medications, in order to mitigate or avoid shortages for the patients that rely on these antibiotics.

The FDA previously set acceptable limits of 0.16 parts per million (ppm) for MNP in rifampin, and 01. ppm for CPNP in rifapentine. However, the agency says it will accept levels of MNP as high as 5 ppm for rifampin, and any level below 14 ppm of CPNP in rifapentine. However, the agency is calling on manufactures to contact the Center for Drug Evaluation and Research’s Drug Shortages Staff when their testing of the drugs shows levels of the nitrosamine contaminants above the normally acceptable intake limits.

“FDA and manufacturers are investigating the origin of these impurities in rifampin and rifapentine, and the agency is developing testing methods for regulators and industry to detect MNP and CPNP in these medicines,” the press release states. “FDA continues its ongoing review, surveillance, compliance and pharmaceutical quality efforts across every product area and will continue to work with drug manufacturers to ensure safe, effective and high-quality drugs for the American public.”

Nitrosamine compounds are a class of chemicals identified as possible human carcinogens. However, the FDA indicates there is no data available which evaluates the cancer-causing potential of MNP or CPNP, which may be why the FDA is allowing drugs containing those compounds to stay on the market.

Another form of nitrosamine, N-nitrosodimethylamine (NDMA), which is strongly linked to a cancer risk, has caused a number of problems in recent months, leading to widespread Zantac recalls, valsartan recalls and metformin recalls.

The FDA is calling on health care professionals and patients who have adverse reactions to rifampin and rifapentine to file a report with the agency’s MedWatch Adverse Event Reporting Program.