Zanaflex Half-Life: How Long Does Tizanidine Stay in Your System?

Last Updated: March 25, 2024

Roger Weiss Authored by Roger Weiss, MD
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Tizanidine is used to treat muscle spasms caused by conditions such as multiple sclerosis, brain injury, or spinal cord injury. It is a fast-acting muscle relaxant that works by slowing the action in the brain and nervous system. However, a few things to note when taking this drug are how long does Tizanidine stay in your system?

Let’s first start by understanding Zanaflex half-life and how much longer it will stay in the system.

Zanaflex Half-Life

Zanaflex half-life refers to the time needed for a drug’s concentration in plasma to be reduced by a percentage of 50%. After the half-life of Zanaflex takes place, the drug’s level in the system will be only half of the initial dose and will help people understand how long Tizanidine lasts.

After administering either a tablet or a capsule of Zanaflex, the peak plasma concentrations of the drug take place one hour after ingestion. The half-life is about two hours to two hours and a half. Almost 95% of a dose is metabolized. The metabolites of Tizanidine are not known to be active, with a half-life varying between 20 and 40 hours.

Food does not influence Zanaflex half-life, but it does affect the peak plasma concentration. In fasting conditions, the peak plasma concentration is one hour after ingestion and has a half-life of around two hours. However, the plasma concentration rises by 30% to one hour and 25 minutes when administered with food.

Blue tablets and white bottle

How Long Does Tizanidine Stay in Your System? Zanaflex Detection Window

A Tizanidine drug test may include a blood, urine, or saliva test to detect the medication traces in the system.  All these tests have a different timeline for which they could pick up the medicine in the body. It has a short half-life of about 2.5 hours. Approximately 95% of the dose gets metabolized, out of which 60% of total radioactivity is recovered in urine. Therefore, a single dose of 4 mg can be detected in urine from 5 to 13 days.

How Long Does Zanaflex Stay in Urine?

It has a short half-life of about. Approximately 95% of the dose gets metabolized, out of which 60% of total radioactivity is recovered in urine. Therefore, a single dose of 4 mg can be detected in urine from 5 to 13 days.

How Long Does Zanaflex Stay in Blood?

A blood test is usually requested when the individual is suspected to be under the influence of a drug. When taken from the blood, Zanaflex drug maximum drug levels on day 1 and falls below the detectable limit by day 5 after ingestion.

How Long Does Zanaflex Stay in Hair?

Tizanidine can be detected in hair and is the most promising alternative test. The Tizanidine drug test is perfect for determining long-term exposure to this drug. The extended detection window for the hair follicle test makes it potentially well suited for detecting drugs. A hair follicle test can help detect the drug only a few days after use for up to 90 days.

How Long Does Zanaflex Stay in Saliva?

A saliva drug test can detect drug use within the first few hours after ingestion, in case it was not detected in urine. Oral secretions can be used to detect the drug in the system for up to 24 to 48 hours after its last use.

Does Zanaflex Show Up on a 12 Panel Drug Test?

Tizanidine is not a controlled drug. Therefore it will not appear on a 12-panel drug test. A 12-panel drug test can turn positive if it is done to detect this medication.

How Long Does Zanaflex Stay in Your System?

The Variables That Affect How Long Does Tizanidine Stay in Your System

Although the half-life of Zanaflex is around two and a half hours, how long does Tizanidine stay in your system varies from one person to another and depends on several factors and variables, which influence this period? The doctor should explain to the patient the Tizanidine mechanism of action, how long Tizanidine stays in your urine, blood, or saliva, as well as factors that play an important role in the drug’s presence in the body.

Such Factors Are:

  • Age: No specific study was conducted to test this. However, a cross-study comparison of the data suggests that young patients can clear out the drug faster from their system compared to elderly patients.
  • Metabolism rate: It has a half-life of 2.5 hrs, where 95% of the dose is metabolized. The metabolites remain inactive and stay up to 20-40 hours.
  • Body mass and weight: A patient's body weight and mass must be calculated before administering any dose. Dose adjustment is required in the case of obese patients. As the drug clearance rate is high for an obese patient so an amount based on lean body weight is recommended, rather than total body weight.
  • Food intake: When the dose was administered with food, the absorption rate increased anywhere between 10 to 30% for capsule and tablet, respectively.
  • Co-administered drugs: such as combining Tizanidine and Flexeril together It's always best to check with the doctor before it in combination with other medications. Tizanidine and Flexeril are both muscle relaxants and should be discussed beforehand with the doctor.
  • Kidney and liver health: Tizanidine is not recommended to patients with Hepatic impairment as it is extensively metabolized in the liver. When it comes to patients with renal problems, Zanaflex half-life must be administered cautiously. Clearance of this drug is reduced by 50% when it is administered to patients with renal impairment.
  • Frequency of administration: In the case of administering a 2 mg dose, a maximum of 3 doses should be taken within 24 hrs, where the effects last for about 6-8 hrs for each dose.

How To Remove Zanaflex From System Safely

Knowing what Tizanidine is and what its mechanism of action is can help the user understand how the medication works and how long Tizanidine lasts in their system. For those who worry about Zanaflex drug testing, there are several things that they can do to help the medication be eliminated from the system faster.

Caution is required, and these should be tried only after asking the doctor about their efficacy and safety.

Calcium D Glucarate

This supplement is said to have detoxifying properties, clearing out the kidneys’ pathways. As most of the Tizanidine is excreted by the kidneys and cleared out through urine, it would make sense that Calcium D Glucarate would help rid the system from the drug faster.

Activated Charcoal

Activated charcoal is sometimes successfully used to treat poisoning or a drug overdose. It decreases the systematic absorption of most toxic substances, as contagions and drugs bind to activated charcoal, helping clean the body and reducing the withdrawal symptoms.


Although drinking water and other liquids will not significantly speed up the elimination of Tizanidine from the body, it can still offer some benefit. Liquid makes the clearance of drugs faster through urine. It should be noted that drinking too much water can be toxic and do more harm than good. Also, hydration might help with some of the Zanaflex side effects, such as dry mouth and constipation.


People that have highly alkaline urine might reabsorb the medication before it is excreted. The pH influences the possibility of the medicine being reabsorbed before excretion. If the drug is reabsorbed, it means that it is re-circulated in the system. To avoid keeping the pH level of urine close to neutral by steering away from red meat, cranberry juice, orange juice, alcohol, and coffee.

Woman with the glass of water

Find The Help One Needs

Knowing the half-life of Tizanidine can help in a possible Tizanidine drug test but also helps the individual to avoid any possible unpleasant withdrawal symptoms if the medication is quit cold turkey. That is why it is important to talk to the doctor or a specialist from a recovery facility regarding any concerns about a possible dependence on this drug. Consult the doctor immediately if faced with hypotension, dry mouth, dizziness, or other symptoms. The doctor might consider replacing the medication with another one.

Any individual can access effective treatment for addiction to drugs in specialized facilities all over the country.

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Page Sources

  1. PRESCRIBING INFORMATION. Zanaflex Capsules. U.S. Food And Drug Administration.,021447s002lbl.pdf
  2. Magnetic molecularly imprinted polymer nanoparticles for selective solid-phase extraction and pre-concentration of Tizanidine in human urine. J Chromatogr B Analyt Technol Biomed Life Sci. 2016.
  3. Barras, M., & Legg, A. (2017). Drug dosing in obese adults. Australian prescriber, 40(5), 189–193.
  4. National Library of Medicine, Tizanidine, 2015
  5. ZANAFLEX- Tizanidine hydrochloride capsule ZANAFLEX- tizanidine hydrochloride tablet Acorda Therapeutics, Inc.

Published on: February 19th, 2020

Updated on: March 25th, 2024

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