Zanaflex and Hypertonia - a phase IV clinical study of FDA data

Summary:

Hypertonia is reported as a side effect among people who take Zanaflex (tizanidine hydrochloride), especially for people who are female, 40-49 old, have been taking the drug for 6 - 12 months also take Avonex, and have Muscle spasticity.

The phase IV clinical study analyzes which people have Hypertonia when taking Zanaflex. It is created by eHealthMe based on reports of 16,325 people who have side effects when taking Zanaflex from the FDA, and is updated regularly.

What is Zanaflex?

Zanaflex has active ingredients of tizanidine hydrochloride. It is often used in muscle spasms. eHealthMe is studying from 17,476 Zanaflex users. Check the latest studies of Zanaflex.

What is Hypertonia?

Hypertonia (abnormal increase in muscle tension and a reduced ability of a muscle to stretch) is found to be associated with 487 drugs and 695 conditions by eHealthMe. Check the latest studies of Hypertonia.

eHealthMe: drug outcomes in the real world

eHealthMe runs one of the largest post-marketing drug safety studies in the world. We study millions of patients and 5,000 more each day. Our data-driven phase IV clinical trials have been referenced on 800+ peer-reviewed medical publications including The Lancet, Mayo Clinic Proceedings, and Nature. Tools to study our phase IV findings are available to the public, anonymous and free >>>.

On Sep, 02, 2026

16,325 people reported to have side effects when taking Zanaflex.
Among them, 61 people (0.37%) have Hypertonia.

Among these 61 people:

How long have people been on Zanaflex when they have Hypertonia? *

What is the gender of people who have Hypertonia when taking Zanaflex? *

female: 65.52 %
male: 34.48 %

What is the age of people who have Hypertonia when taking Zanaflex? *

What are other drugs people take besides Zanaflex? *

What are other side effects people have besides Hypertonia? *

Weakness: 11 people, 18.03%
Influenza Like Illness: 10 people, 16.39%
Multiple Sclerosis Aggravated (a nervous system disease that affects your brain and spinal cord. it damages the myelin sheath): 10 people, 16.39%
Fever: 9 people, 14.75%
Muscle Spasticity (tight or stiff muscles and an inability to control those muscles): 7 people, 11.48%
Lambert-Eaton Syndrome (this means your immune system mistakenly targets healthy cells and tissues in the body): 6 people, 9.84%
Musculoskeletal Stiffness (stiffness of the body's muscles, joints, tendons, ligaments and nerves): 6 people, 9.84%
Hypoaesthesia (reduced sense of touch or sensation): 6 people, 9.84%
Oedema Peripheral (superficial swelling): 5 people, 8.20%
Back Pain: 5 people, 8.20%

What are the existing conditions these people have? *

Muscle Spasticity (tight or stiff muscles and an inability to control those muscles): 12 people, 19.67%
Secondary Progressive Multiple Sclerosis (a stage of ms which comes after relapsing remitting ms in many cases): 2 people, 3.28%
Multiple Sclerosis (a nervous system disease that affects your brain and spinal cord. it damages the myelin sheath): 2 people, 3.28%
Nausea (feeling of having an urge to vomit): 1 person, 1.64%

* Approximation only. Some reports may have incomplete information.

Do you take Zanaflex and have Hypertonia?

- Check whether Hypertonia 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 Zanaflex:

Zanaflex (17,476 reports)

Hypertonia treatments and more:

Hypertonia (11,073 reports)

Browse all side effects of Zanaflex:

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 Hypertonia:

Hypertonia (487 drugs)

Browse all the conditions that are associated with Hypertonia:

Hypertonia (695 conditions)

How the study uses the data?

The study uses data from the FDA. It is based on tizanidine hydrochloride (the active ingredients of Zanaflex) and Zanaflex (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.