Benadryl With Synthroid And Prednisone

Krush asked

Is Benadryl safe to take while on Synthroid and prednisone?

Answer

There is no drug interaction between Benadryl (diphenhydramine), Synthroid (levothyroxine) and prednisone. However, it is important to follow the recommended dosing instructions for all of these medications, especially Synthroid, to avoid potential interactions.

Synthroid (levothyroxine) should generally be taken by itself, on an empty stomach at least 30 minutes before food or beverages (besides water) for optimal absorption. Taking it at the same time as Benadryl or prednisone could potentially decrease absorption.

All in all, Benadryl and prednisone are considered safe to take the same day as Synthroid, just not at the same time.

There is a general precaution that you should be aware of concerning the administration of corticosteroids (like prednisone) and thyroid replacement medications (like Synthroid). I cover that in the next section.

Corticosteroids And Thyroid Function

It is important to note that taking a corticosteroid, such as prednisone, can cause short-term changes in thyroid hormone concentrations. The prescribing information for Synthroid states the following:

Short-term administration of large doses of glucocorticoids [e.g. prednisone] may decrease serum T3 concentrations by 30% with minimal change in serum T4 levels. However, long-term glucocorticoid therapy may result in slightly decreased T3 and T4 levels due to decreased TBG [ Thyroxine-binding globulin].

Nevertheless, the short-term use of prednisone generally does not elicit major changes. Thyroid hormones and corticosteroids are often used together without significant interactions.

However, if you do notice any side effects (e.g. fatigue, changes in mood, feeling of cold, etc...), be sure to see your doctor as there could potentially be a decrease thyroid hormone concentrations.