The worsening of symptoms in 52% of previously stabilized patients with heartburn or gastroesophageal reflux disease when their treatment is switched from omeprazole to lansoprazole therapy as described by Nelson et al1 raises several disturbing issues. First, this switch was made after the Pharmacy and Therapeutics Committee of Unity Health Plans declared the 2 drugs to be "therapeutically interchangeable."1 Even if it is assumed that omeprazole and lansoprazole have equivalent therapeutic efficacy, this does not mean the drugs will have similar efficacy in individual patients. Among other drug groups, switching treatment from therapeutically equivalent drugs such as ibuprofen to celecoxib or fluoxetine to sertraline frequently produces altered responses.
Cohen JS. Clinical and Ethical Concerns About Switching Patient Treatment to "Therapeutically Interchangeable" Medications. Arch Intern Med. 2001;161(17):2153-2154. doi: