19 May 2017 - New medicines that win U.S. marketing approval without conclusive evidence of their effectiveness aren't always proven to work after they go on sale, a recent research review suggests.

Researchers focused on medicines approved for sale based on single pivotal trials or based on what's known as "surrogate markers," such as lab tests and signs of risk for disease such as cholesterol levels instead of true clinical outcomes like heart attacks or deaths. Many times no follow-up studies were published after these medicines went on sale, and when studies were published they often continued to rely on surrogate markers to suggest potential effectiveness.

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