Three groups representing 4600 US endocrinologists have said in a public statement that they are “deeply disappointed” that the Food and Drug Administration has approved generic substitutes for brandname levothyroxine. Patient groups have welcomed the news, however, with one group announcing on its website: “The Generics are Coming, The Generics are Coming!!!” (www.thyroid.about.com/od/thyroiddrugtreatments/a/generic.htm).

Levothyroxine is the second most commonly prescribed drug in the United States, with sales worth $1.19bn (£0.64bn; €0.96bn) in 2003. Abbott Laboratories' market leader, Synthroid, had sales of nearly $820m, says IMS Health, a major pharmaceutical information and consulting company. More than 13 million people take the drug.

The American Thyroid Association, the Endocrine Society, and the American Society of Clinical Endocrinologists said: “Small differences between doses—well within the range of formulation differences that might …