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Antibiotics have been one of the miracles of modern medicine and can be lifesavers in the right context. Unfortunately, there are significant downsides to many of these antibiotics and those suffering from thyroid conditions have to be aware of a specific class of antibiotics known as quinolones or fluoroquinolones.

This group consists of more than 60 generic versions – here are a few:

Ciprofloxacin Cipro Ciloxan eye drops Levofloxacin
Levaquin Quixin Moxifloxacin Avelox
Vigamox eye drops Norfloxacin Noroxin Ofloxacin
Ocuflox Floxin Floxin Otic Floxacin
Trovafloxacin Trovan Alatrofloxacin Baxdela
Factive Avelox Delafloxacin gemifloxacin


For people with thyroid disease, these antibiotics are especially worrisome because the quinolone antibiotics are built with a fluoride backbone. It is important to note that fluoride is extremely toxic to your thyroid and I am not a fan of fluoride coming anywhere near your thyroid gland.

Fluoride like bromide, iodide, and chloride are all halides and structurally similar. This structural similarity allows the fluoride molecules in these antibiotics to compete for the iodide receptors in the thyroid gland which uses iodine to make thyroid hormones. This competition for binding sites in the thyroid can create havoc for this important and sensitive gland.

Furthermore combining quinolone antibiotics withT4 drugs (Levothyroxine – Synthroid, Tirosint, Levoxyl, Unithroid, Levo-T) can alter the absorption of thyroid medicine and lead to changes in TSH making it difficult to manage the dosing of the prescription.

Some of these medications have been pulled off the market, and the remaining drugs have a “Black Box” warning on them from the FDA.

If prescribed an antibiotic PLEASE check with your physician or pharmacist to see if it is in the fluoroquinolone family. Ask for alternatives and point out that the FDA only recommends this class of antibiotics for serious infections.

Side effects can look like just about every thyroid symptoms out there and include severe insomnia, hypnic jerks, tendon and cartilage tears, brain fog, skin crawling sensations, headaches, buzzing, pain, tinnitus (ear ringing), severe fatigue, moving abdominal pain and many more.

If you have questions about any of this, please don’t hesitate to reach out. It is my mission to make sure you are able to feel your best and managing your health and well-being is a huge part of that.

-Dr. Jerome Craig


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