Revised monograph for levothyroxine to be issued in USA

The US Pharmacopeial Convention is in the process of revising its monograph for levothyroxine sodium, a commonly-prescribed synthetic thyroid hormone branded as Synthroid in the USA and Eltroxin in Asia, Europe and Oceania. The revised monograph will go into effect on October 3, 2009, and is part of Food and Drug Administration's plan to address concerns about the variability in the stability profile of levothyroxine sodium products, particularly in achieving target thyroid levels in vulnerable patients.

The FDA narrowed the assay range for levothyroxine sodium in an attempt to standardize and limit potency across manufacturers. Recently, there has been a global public outcry among patients that have experienced adverse side effects due to differentiations in the formulation and manufacturing of the drug. The revised monograph supports the agency's goal of achieving stability through limiting allowable potency degradation over the drug's shelf life.

The FDA has worked closely with companies licensed to market levothyroxine sodium tablets in the USA to determine the new potency range, but many non-US markets have a local regulatory commitment to observe USP standards, and manufacturers in these countries will need to meet the revised standard once official. It is of high clinical importance that these firms are aware of the change so that the supply of levothyroxine sodium tablets is not disrupted by compliance issues.