Flexeril and Low thyroid - a phase IV clinical study of FDA data

Summary:

Low thyroid is reported as a side effect among people who take Flexeril (cyclobenzaprine hydrochloride), especially for people who are female, 40-49 old, have been taking the drug for 10+ years also take Synthroid, and have Pain.

The phase IV clinical study analyzes which people have Low thyroid when taking Flexeril. It is created by eHealthMe based on reports of 34,789 people who have side effects when taking Flexeril from the FDA, and is updated regularly.

What is Flexeril?

Flexeril has active ingredients of cyclobenzaprine hydrochloride. It is often used in muscle spasms. eHealthMe is studying from 38,307 Flexeril users. Check the latest studies of Flexeril.

What is Low thyroid?

Low thyroid (abnormally low thyroid hormone production) is found to be associated with 2,692 drugs and 2,633 conditions by eHealthMe. Check the latest studies of Low thyroid.

On Mar, 19, 2026

34,789 people reported to have side effects when taking Flexeril.
Among them, 274 people (0.79%) have Low thyroid.

Among these 274 people:

* Approximation only. Some reports may have incomplete information.

Do you take Flexeril and have Low thyroid?

- Check whether Low thyroid is associated with a drug or a condition
- Predict drug outcomes for up to one year with AI
- Get an AI agent to monitor your drugs continuously

Related studies:

Effectiveness of, long term effects of, and alternative drugs to Flexeril:

Flexeril (38,307 reports)

Low thyroid treatments and more:

Low thyroid (168,056 reports)

How severe was Low thyroid and when was it recovered:

Low thyroid in Flexeril

Expand to all the drugs that have ingredients of cyclobenzaprine hydrochloride:

Low thyroid and drugs with ingredients of cyclobenzaprine hydrochloride (637 reports)

Sub-studies by gender and age:

Female: 0-1 2-9 10-19 20-29 30-39 40-49 50-59 60+

Male: 0-1 2-9 10-19 20-29 30-39 40-49 50-59 60+

Browse all side effects of Flexeril:

a b c d e f g h i j k l m n o p q r s t u v w x y z

Browse all the drugs that are associated with Low thyroid:

Low thyroid (2,692 drugs)

Browse all the conditions that are associated with Low thyroid:

Low thyroid (2,633 conditions)

How the study uses the data?

The study uses data from the FDA. It is based on cyclobenzaprine hydrochloride (the active ingredients of Flexeril) and Flexeril (the brand name). Other drugs that have the same active ingredients (e.g. generic drugs) are not considered. Dosage of drugs is not considered in the study.

How to use the study?

DO NOT STOP MEDICATIONS without first consulting your doctor. If there are any serious or long term adverse effects discovered in the study, discuss the study with your doctor to ensure that proper medication management will be in place if applicable.

Who is eHealthMe?

With medical big data and proven AI/ML algorithms, eHealthMe provides a platform for everyone to run phase IV clinical trials. We study millions of patients and 5,000 more each day. Results of our real-world drug study have been referenced on 800+ peer-reviewed medical publications, including The Lancet, Mayo Clinic Proceedings, and Nature. Our analysis results are available to researchers, health care professionals, patients (testimonials), and software developers (open API).

WARNING, DISCLAIMER, USE FOR PUBLICATION

WARNING: Please DO NOT STOP MEDICATIONS without first consulting a physician since doing so could be hazardous to your health.

DISCLAIMER: All material available on eHealthMe.com is for informational purposes only, and is not a substitute for medical advice, diagnosis, or treatment provided by a qualified healthcare provider. All information is observation-only. Our phase IV clinical studies alone cannot establish cause-effect relationship. Different individuals may respond to medication in different ways. Every effort has been made to ensure that all information is accurate, up-to-date, and complete, but no guarantee is made to that effect. The use of the eHealthMe site and its content is at your own risk.

If you use this eHealthMe study on publication, please acknowledge it with a citation: study title, URL, accessed date.