Excipients are literally the stuff of placebos; they are the nonactive ingredients that allow manufacturers to compound a drug into a comestible pill with a reasonable shelf life. When Merck changed the excipients in the thyroid hormone replacement drug Levothyroxine from mannitol plus citric acid to lactose, it set off a virtual firestorm. Before releasing the new formulation, Merck had conducted a randomized bioequivalence study that found that the biological outcome measures were essentially identical and the new formulation was completely safe. Nonetheless, patients reported significant side effects; from hair loss, headaches, and weight gain, to diarrhea, extreme fatigue, and increased heart rates, the rash of side effects experienced by the tens of thousands of patients with hypothyroidism in France gave rise to more than sixty lawsuits accusing Merck and the French government of a “failure to assist a person in danger.”18
From:
The MIT Press Essential Knowledge
Placebos
Kathryn T. Hall