Decisions to approve, prescribe and consume medicines involve risk/benefit assessments by regulatory agencies, health care professionals and consumers. For serious or life threatening conditions, drugs with higher risks for adverse effects or for serious adverse effects are sometimes acceptable. For example, some life-saving cancer chemotherapies are known human carcinogens. However, if one is suffering from a life threatening tumor, a 5% risk of a secondary, treatment-related tumor is generally considered acceptable. Arguably, the same is not true for impurities found in drug substances and drug products; impurities convey only risk with no associated benefit. Drug impurities might be viewed as “pollutants” in the pharmaceutical world. Much like pollutants in the environment, few people believe that they can be entirely eliminated. The challenge for regulatory agencies is to promulgate standards that assure that unavoidable drug impurities impart no or acceptable levels of risk.
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