Does Omeprazole Interact With Thyroid Medication?

Hi Abycat and thank you for reaching out to us.

There is a potential interaction between any proton pump inhibitor (e.g. Prilosec (omeprazole)) and most medications used to treat hypothyroidism (such as Cytomel (liothyronine) and Nature-Throid).

Proton pump inhibitors alter the acidity of the stomach, something which studies have shown can decrease the absorption of thyroid hormone prescription products.

Some of the published data on the matter is conflicting, but overall, it would be prudent to monitor for an altered response to your thyroid medications if you are taking a PPI.

Proton Pump Inhibitors

Omeprazole, or under the brand name Prilosec, is a proton pump inhibitor. It works by inhibiting the proton pumps in your stomach. This decreases the acidity of your stomach contents (which is why it can interact with thyroid prescription products).

It’s commonly prescribed to treat gastroesophageal reflux disease or a host of other stomach conditions. It is available over the counter and by prescription.

In regard to over the counter use, it is usually safe to take for a week or two, but oftentimes, people take it every day, and for longer periods of time.

Continuous use can lead to a lot of long term complications, such as vitamin and mineral deficiencies and an increased risk of infection. If you feel you need to use a PPI for a long period of time, be sure to see your doctor to make sure it represents the best therapy for you.

Cytomel & Nature-Throid

Cytomel (or by the generic name liothyronine) and Nature Thyroid are thyroid hormones taken to correct your own thyroid not producing enough thyroid hormone (or other associated conditions).

Specifically, Cytomel contains T₃, or liothyronine, while Nature-Throid is referred to as desiccated thyroid, and contains both T₃ and T₄.

Both are usually taken once a day, first thing in the morning on an empty stomach. They are taken this way so that they are absorbed consistently since thyroid hormones are difficult to dose. A small change in absorption may lead to decreased thyroid levels and you beginning to feel the effects of hypothyroidism.

The Interaction

Unfortunately, as mentioned, there is a known drug interaction between omeprazole (and other similar medications) and thyroid hormone drugs.

Omeprazole, regardless of when it is taken, reduces the amount of thyroid hormone that is absorbed and it is recommended to avoid the combination or, at the very least, be prudent in monitoring your thyroid levels if taken together.

One study on this interaction, published in the Journal of General Internal Medicine, concluded the following:

The concomitant use of LT4 [levothyroxine] and PPI showed a significant increase in TSH concentration. However, given the small number of studies, further research is needed to clarify the interfering role of PPI on LT4 intestinal absorption.

Even the medical guidelines for hypothyroidism reference the interaction between PPI drugs and thyroid hormone prescriptions (specifically levothyroxine):

The list of medications that can alter the absorption of LT4 [levothyroxine] is extensive and includes calcium carbonate, PPIs , bile acid sequestrants (cholestyramine and colesevelam), phosphate binders, ferrous sulfate, aluminum-containing antacids, and sucralfate.

If you are constantly having stomach issues and need to be on omeprazole or another proton pump inhibitor, your physician may at some point have to increase your thyroid hormone dose (based on what your labs are showing) to account for this decreased absorption.

I want to point out that most studies have researched the effects of PPIs and levothyroxine specifically, not necessarily Cytomel and Nature-Throid. Nevertheless, as they are all thyroid hormones, and have similar absorption properties, they are generally included with levothyroxine as far as interactions are concerned.

I also want to say that not every study shows these same results. Some smaller ones (such as this one) have noted no difference in thyroid levels in those taking a PPI.

The takeaway point is that there is likely a clinically significant interaction, but some people may be more affected than others.

What To Do

Simply separating the time you take PPI (such as omeprazole) from your thyroid medications will not avoid the interaction.

Proton pump inhibitors, when taken consistently, have a long duration of action. They can alter the stomach acid for well over 24 hours after dosing (which is why they are generally dosed once daily). So, unfortunately, taking, say, omeprazole in the morning and your thyroid medications in the evening, won't do much good.

If being on a PPI has been determined by you and your doctor to be your best treatment option, be sure to have your thyroid levels tested a few times after starting omeprazole. You may notice your TSH levels going up (which is indicative of hypothyroidism). From there, an adjustment to your dose may be necessary.

Overall, I would expect a few months where your TSH levels are fluctuating, but over time, things should get more consistent.

If you want to avoid PPIs, like omeprazole, you do have a few other over the counter options for occasional heartburn that don't have the associated interaction.

First, an antacid like calcium carbonate (Tums) is safe to take with thyroid hormones, as long as you are taking it at least 4 hours after your thyroid hormone dose. Also, over the counter famotidine (Pepcid) is a safer option than PPIs, if separated by 12 hours or more from thyroid hormones.

If you do experience frequent heartburn or GI symptoms, it might be a good idea to schedule an appointment and follow up with your physician.

Thanks for reaching out to us and I hope this helps!