I wondered too much to let it slide, so I found the answer at StraightDope.com:
What happened to Mercurochrome?
23-Jul-2004
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Dear Cecil:
I had skin surgery recently and was told to apply Mercurochrome to aid in scarless healing. The product, once widely available, is sold by only one vendor in Boise, and I'm told they manufacture their own. Another pharmacist told me they were not allowed to handle or sell it. What happened to this antiseptic that I grew up with? --David Young, Boise, Idaho
Cecil replies:
You're dating yourself, pops. Few under age 30 have ever heard of this stuff. In 1998, the U.S. Food and Drug Administration declared that Mercurochrome, generically known as merbromin, was "not generally recognized as safe and effective" as an over-the-counter antiseptic and forbade its sale across state lines. A few traditionalists complained: Whaddya mean, not generally recognized as safe? Moms have been daubing it on their kids' owies since the Harding administration! But the more reasonable reaction was: It's about time.
For many years the FDA, faced with the task of regulating thousands of pharmaceuticals and food additives, many of which long predated federal oversight, has maintained the so-called GRAS (generally recognized etc) list, originally compiled as a way of grandfathering in products like Mercurochrome that had been around for ages and hadn't hurt or killed a noticeable number of people. Recognizing that from a scientific standpoint such a standard left a lot to be desired, the FDA has been whittling away at the unexamined products on the GRAS list over time. Mercurochrome and other drugs containing mercury came up for scrutiny as part of a general review of over-the-counter antiseptics that began in 1978, and for good reason--mercury in large enough doses is a poison that harms the brain, the kidneys, and developing fetuses. While no one's offered evidence of mass Mercurochrome poisoning, the medical literature contains scattered reports of mercury toxicity due to use of the antiseptic, and these days the burden of proof is on drug manufacturers to show that their products' benefits outweigh the risks. In the case of Mercurochrome and many other mercury-containing compounds, that had never been done.
The FDA initially proposed clipping Mercurochrome's GRAS status in 1982 and asked for comment. Hearing little, the FDA classified the antiseptic as a "new drug," meaning that anyone proposing to sell it nationwide had to submit it to the same rigorous approval process required of a drug invented last month. (This took place in 1998--nobody's going to accuse the FDA of rushing to judgment.) It's not out of the question that a pharmaceutical company will do so someday--published research on Mercurochrome, though hardly abundant, suggests the stuff is reasonably effective. However, the approval process is time-consuming and expensive and any patent protection Mercurochrome might once have had surely expired long ago. For the foreseeable future those yearning for that delicious Mercurochrome sting will have to look somewhere else.
