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New Standards Released for Drug Impurity Limits, Methods

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U.S. Pharmacopeial Convention (USP) in Rockville, Maryland has published two new standards governing elemental impurities in medications. USP says conformance to the standards will be required starting 1 May 2014.

Elemental impurities include catalysts and environmental contaminants such as lead or mercury that may be present in drugs. According to USP, elemental impurities can occur naturally, be added intentionally, or introduced inadvertently, such as through interactions with processing equipment.

The standards specify the limits for elemental impurities (General Chapter 232) and procedures for the detection of selected impurities in drug products based on current analytical methods (General Chapter 233). Of the 15 elemental impurities identified for testing in Chapter 232, 11 are catalysts, and thus says USP, their presence in a given drug product would be known through an assessment of the manufacturing process. The remaining four specified elements — arsenic, cadmium, lead, and mercury — are naturally occurring or environmental impurities, thus making it necessary to assess the likelihood of their presence.

USP says the analytical procedures in chapter 233 indicate the technologies inductively coupled plasma–atomic (optical) emission spectroscopy (ICP-AES) and inductively coupled plasma–mass spectroscopy (ICP-MS) to detect elemental impurities. The chapter also describes criteria for validation and verification of the procedures and for the establishment of acceptable alternative procedures.

According to USP, the previous standards for elemental impurities published in chapter 231 on heavy metals applied only to active pharmaceutical ingredients and excipients, such as inert diluting agents or delivery substances. The organization adds that the test methods described in that chapter are not considered sufficiently sensitive to detect some of the impurities at levels known to be toxic.

USP is a not-for-profit standards-setting organization that helps ensure the quality, safety, and benefit of medicines and foods. The texts of both general chapters can be accessed on USP’s Web site.

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