Many women have, for decades, taken a drug called phenazopyridine to control pain from urinary tract infections. Sold under such brand names as Azo and Uristat, it’s available in most US pharmacies or groceries with a well-stocked health aisle and doesn’t require a prescription. Target Corp. and Walmart Inc. both offer their own generic versions.
Given the ease of purchase, it’s a good bet many users assume the drug has been vetted by US regulators and found to be safe and effective. It hasn’t. In fact, the Food and Drug Administration 20 years ago raised questions about whether it truly works, ...