Levothyroxine Formulations

Two new brands of levothyroxine were added to the Pharmaceutical Benefits Scheme (PBS) on 1st February 2022. These new brands, Eltroxin® and Levoxine®, join the existing listings of Eutroxsig® and Oroxine®. 

These medications are all indicated for the treatment of thyroid hormone deficiency and to suppress thyroid-stimulating hormone (TSH) in the management of TSH-responsive tumours. However, not all brands are considered bioequivalent.  

Eutroxsig® and Oroxine® are the same formulation and can be used interchangeably. Eltroxin® is a more stable formulation, enabling it to be stored at room temperature (below 25°C). However, this formulation change is thought to lower its bioavailability, and it should not be used interchangeably with other brands. If patients are switched to or from the Eltroxin® brand, TSH levels should be evaluated and the levothyroxine dose adjusted, if necessary. The Levoxine® brand is also shelf-stable but is considered bioequivalent to Eutroxsig® and Oroxine®.  

A summary of these differences is shown in Table 1. 

Table 1. Overview of levothyroxine brands 

  * Levoxine®, Eutroxsig®, and Oroxine® are a-flagged on the PBS.