Nitrosamine impurities have been identified in samples of rifampin and rifapentine, according to the Food and Drug Administration (FDA).

Specifically, the rifampin samples included 1-methyl-4-nitrosopiperazine (MNP), while the rifapentine ones contained 1-cyclopentyl-4-nitrosopiperazine (CPNP). Both of these impurities belong to the nitrosamine class of compounds. Currently, there is no available evidence to assess the carcinogenic potential of MNP and CPNP.

Both rifampin and rifapentine are indicated for the treatment of tuberculosis. To avoid a potential shortage of these drugs, the FDA is allowing manufacturers to temporarily distribute products with impurities above the acceptable intake limits while an investigation into the source continues. In a press statement, the Agency noted that it “will not object to these higher exposures to maintain patient access to these life-saving medications.”

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In the meantime, the FDA is working to develop testing methods for manufacturers to aid in the detection of MNP and CPNP.  Products that show levels of nitrosamines that exceed the limits set forth by the Agency will need to be evaluated on a case-by-case basis before they are released for distribution.

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FDA works to mitigate shortages of rifampin and rifapentine after manufacturers find nitrosamine impurities. Accessed August 27, 2020.