21 May 2021
Levothyroxine: New prescribing advice for Health Professionals
The UK’s Medicines and Healthcare products Regulatory Authority (MHRA) has issued new prescribing advice for health professionals regarding patients who experience issues when switching between different levothyroxine products.
Many of us on lifelong levothyroxine tablets are given a different make of the drug with each prescription. While many of us see no difference, some people may experience variable thyroid function and the symptoms that accompany that.
However, now, if a patient reports persistent symptoms when switching between different levothyroxine tablet formulations, doctors are being asked to consider consistently prescribing a specific product known to be well tolerated by the patient. In addition, if those symptoms or the poor control of thyroid function persist (despite adhering to a specific product), doctors should consider prescribing levothyroxine in an oral solution formulation.
To reach this decision, the MHRA considered a variety of data, including 335 Yellow Card reports submitted between 2015-2019 (mainly from patients) reporting problems when switching between different makes of levothyroxine.
It’s great that these people have been listened to and the advice updated accordingly. This will certainly come as a relief to those people who are particularly sensitive to switching makes of levothyroxine. If you are one of those people, then make sure your GP knows about this update, and work with them and your endocrinologist to find the best formulation for you.
Why do Some People Struggle with Different Formulations?
The underlying causes for the symptoms experienced by patients switching between levothyroxine products are generally unclear, but could include:
- gut problems that affect levothyroxine absorption
- use of stomach acid-reducing medicines (such as PPIs) at the same time, which can also affect levothyroxine absorption
- very low thyroid reserve
- intolerance or allergy to an excipient in a particular brand
- a person’s genetic make-up altering how thyroid hormone is taken in by the body, or how it works
Who is Prescribed Levothyroxine?
The majority of our members taking levothyroxine will have had thyroid surgery to remove the gland due to medullary thyroid cancer, and have multiple endocrine neoplasia (MEN) type 2A or MEN type 2B. Many people with MEN2B also have gut issues that may affect levothyroxine absorption. Those with MEN type 1 may also be on levothyroxine after removal of parathyroid glands embedded within the thyroid gland.