USA – Good real-world outcomes for generic levothyroxine, despite narrow therapeutic index

Generic versions of levothyroxine – a treatment for hypothyroidism — are just as effective in restoring thyroid stimulating hormone levels as brand-name drugs in a real-world population, according to a recent study conducted by researchers from the US Food and Drug Administration, Yale University, and the Mayo Clinic.
 
Generic levothyroxine is prescribed about six-to-one over branded levothyroxine, but that still leaves generic prescriptions lagging behind prescribing rates in other drug categories, the FDA says. Part of the hesitancy to prescribe the generic version of the drug may stem from the fact that levothyroxine has a narrow therapeutic index
 
Additionally, endocrine professional societies raised safety concerns following FDA’s initial approval of several generic levothyroxine products. The groups called into question FDA’s method for determining bioequivalence for thyroid products. In response, the agency tightened the potency specifications for levothyroxine sodium, changing the potency specification from 90%-110% to 95%-105%…