Bayer's Silver Bullet

Just two months ago, shares in the German chemical giant Bayer fell sharply after the company withdrew a cholesterol-lowering drug from the market in the wake of 52 related deaths. Now those shares have partly bounced back because of another tragedy: Bayers antibiotic Cipro is the drug of choice for treating anthrax, the deadly illness that has infected one person in Kenya, several in the U.S. — and terrorized millions around the world.

Talk about a silver lining. As worried Americans rushed out to buy Cipro — 14,800 prescriptions were filled in New York City in just one...