How long does Zanaflex Stay in your System?

How long does Zanaflex Stay in your System?

Tizanidine, sold under the brand name Zanaflex, is a prescription medication used to treat the symptoms of muscle spasticity due to multiple sclerosis or spinal cord injury. The medication belongs to a class of drugs called Central Alpha-2-Adrenergic Agonist. It can be used along with other medicines or alone too. The drug was approved by FDA in 1996 in the United States for medical use. Zanaflex is available as a generic medication. With more than 8 million prescriptions, it was the 86th most commonly prescribed medication in the United States in 2018. Zanaflex is a central alpha-2-adrenergic receptor agonist & it reduces the spasticity by increasing the presynaptic inhibition of motor neurons. The effects of the medication are most remarkable on the polysynaptic pathways. The complete impact of these actions is thought to alleviate the simplification of spinal motor neurons. While oral administration of the drug, it is completely absorbed. (Kaddar, N., Vigneault, P., Pilote, S., Patoine, D., Simard, C. and Drolet, B., 2012)

Half-life of Zanaflex

The active ingredient in Zanaflex is Tizanidine and is used in treating antispastic in multiple sclerosis and spinal cord injury. The half-life of Zanaflex is approximately 2.5 hours, but its metabolites have a half-life of about 20 hours to 40 hours. Hence, a single dose of the medication will take approximately 80-90 hours to get out of the system completely. .After taking either a tablet or capsule of Zanaflex, the peak plasma concentrations occur an hour after ingestion. The half-life of the drug is about two hours to two and a half. Almost 95% of the dose is metabolized. With a half-life varying between 20 to 40 hours, the metabolites of Zanaflex are not known to be active. The half-life of Zanaflex is not influenced by food, but it does affect the peak plasma concentration. In the fasting state, the peak plasma concentrations. In a fasting state, the peak plasma concentration is one hour after ingestion & a half-life of about two hours.  However, Zanaflex, when administered with food, the plasma concentration rises by 30% to one hour and 25 minutes. (Granfors, M.T., Backman, J.T., Neuvonen, M. and Neuvonen, P.J., 2004)
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Factors that Affect how long Zanaflex Stay in your System

Though the half-life of Zanaflex is approximately 2 to 2.5 hours, it varies from person to person; how long will it stay in your system depending on several factors and variables? The healthcare physician must explain the mechanism of Zanaflex, how long it will remain in your system, urine, blood, or Saliva, and the factors that play a vital role in the drug’s presence in the body.

The factors include:

  • Age
  • Metabolism rate
  • Body mass and weight
  • Food intake
  • Co-administered drug
  • Kidney and liver health
  • Frequency of administration 

Zanaflex in Urine: It has a short half-life; approximately 95% of the dose gets metabolized, out of which 60% is recovered in urine. Therefore a single dose of 4mg can be detected in urine from 5 to 13 days.

Zanaflex in Blood: A blood test is requested when an individual is suspected to be under the influence of drugs. When taken from blood, Zanaflex is found maximum on day 1 & falls below the detectable limit by day 5 after ingestion.

Zanaflex stay in hair: Zanaflex can be detected in hair & is the most promising alternative test as it is perfect for examining long-term use of the drug. A hair follicle test can help detect the drug for up to 90 days.

Zanaflex stay in Saliva: A saliva drug test can detect the presence of drugs within a few hours after ingestion. Oral secretions may be able to show if you’ve been using for up to 24-48 hours, depending on how long it’s been used.

How to remove Zanaflex from the System Safely?

Knowing the mechanism of Zanaflex and what Zanaflex is can help us understand the working and efficiency of the medicine and how long it will remain in your system. For the individual who worries about the Zanaflex testing, there are many things they can do to help in order to get the medication eliminated from the system at a faster rate. Precautions are required, and these should be considered only under the guidance of your healthcare physician. Following are the methods-
  • Calcium D Glucarate
  • Activated Charcoal
  • Hydration
  • Acidification
It is always advised to talk or consult your healthcare physician regarding every concern about dependence on this drug. Seek immediate medical help if you are experiencing dry mouth, hypertension, dizziness, or other symptoms after administering the drug. Your healthcare physician might consider replacing it with any other medication. (Suárez-Lledó, A., Padullés, A., Lozano, T., Cobo-Sacristán, S., Colls, M. and Jódar, R., 2018)
Zanaflex vs Robaxin

Zanaflex vs Robaxin

The generic name for Zanaflex is tizanidine, and it acts as a short-acting muscle relaxer. It mainly works by blocking the pain sensations, i.e., nerve impulses directed to your brain. 

Conditions like cerebral palsy or other neurological disorders are treated by Zanaflex, which is a prescription medicine. The symptoms like muscle stiffness (spasticity) are associated with the neurological disorder is treated by this drug. Zanaflex may be safe and effective for children, but it’s not known if they work because there has never been a clinical trial on them before. The safety and effectiveness data explicitly related to children under 18 has not yet been published; however, this does not mean you shouldn’t give them one chance if your child falls.

The generic name of Robaxin is methocarbamol which is also a muscle relaxer to treat skeletal muscle conditions such as injury.mRobaxin is a prescription medicine used to treat the symptoms of muscle spasms caused by pain or injury and Tetanus. 

They belong in a group known as Skeletal Muscle Relaxants, which includes Valium, among others; not only does it help relieve your discomfort, there has been some evidence suggesting these drugs can actually decrease seizures from epilepsy conditions such as Lennox Gas taut Syndrome.

Are Robaxin and Zanaflex the same thing?

Zanaflex and Robaxin are both muscle relaxants which is used for relaxing the muscles in slightly different ways. Robaxin can be used with therapy and rest to treat skeletal muscle conditions such as injury and pain.

If your muscles suffer cramping after a workout or swimming, then you could use Zanaflex to treat them. It also uses for muscle tightness, the condition like spasm is caused by conditions such as spinal injury.

You may see similar side effects of Zanaflex and Robaxin, including dizziness, skin rash, drowsiness, vomiting, and constipation. It’s not like there are only similar side effects of Robaxin and Zanaflex; some side effects of Robaxin are different from Zanaflex that includes:

  • Nausea
  • Stomach upset
  • Confusion
  • Loss of balance or co-ordination
  • Headache
  • Blurred vision
  • Memory problems
  • Eye redness
  • Spinning sensation
  • Stuffy nose
  • Itching
  • Sleep problems
  • Double vision
  • Diarrhea
  • Dry mouth
  • Fever
  • Muscle weakness
  • Sweating
  • Fatigue
  • Numbness or tingling
  • Back pain
  • Increased muscle tone or spasms
  • Nervousness
  • Anxiousness

Studies have shown that both drugs Zanaflex and Robaxin may interact with some other medicines that can make your breathing slow and could make you dizzy and sleepy. Other drugs may include prescription cough medicines, anxiety, sleeping pills, and depression, narcotics, and muscle relaxers. It is seen that if consumption of Zanaflex stops suddenly after long-term use, then you may have some withdrawal symptoms like anxiety, fast heartbeats, tremors, and dizziness.

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Strength of Robaxin and Zanaflex

Strength of Robaxin and Zanaflex
  • Robaxin is available in round, a light orange film-coated tablet that contains 500 mg of methocarbamol and USP for oral administration.
  • Zanaflex capsules are available in three strengths containing tizanidine hydrochloride, a two-piece hard gelatin capsule. It has 2.29 mg. 4.58 mg and 6.87 mg, equivalent to 2 mg, 4 mg, and 6 mg tizanidine base.

How is Robaxin taken?

Doctors have recommended the doses of Robaxin so that you may not overdose on it. The recommended started dose is six grams a day for the first 48 to 72 hours of the treatment; after some time, you may reduce these doses to approximately 4 grams a day which might not affect you adversely.

If you are using the medicines regularly, tell your doctor or healthcare provider about all over-the-counter prescriptions, medications, and supplements you use.

Robaxin is prescribed for women during pregnancy, but research has not proven whether this drug passes into breast milk? So consult a doctor if you’re using this drug and breastfeeding.

How is Zanaflex taken?

consume robaxin

Zanaflex is a strong drug, and it should be taken only if recommended and precisely as prescribed; you can take it with or without food and be aware that you do not switch between capsules and tablets.

Patients must be informed about this drug that they should not consume Zanaflex more than prescribed because there might be a risk of adverse effects at single doses greater than 8 mg or total daily doses greater than 36 mg.

Like Robaxin, the patient must be informed about the Zanaflex that it should be suddenly stopped because tachycardia and rebound hypertension may occur.

Robaxin Precautions

First to remember, if you’re allergic to Robaxin, then tell your doctor or pharmacist about it to suggest you some advice. The drug may contain some inactive ingredients that may be harmful or cause some allergic reactions or other problems to your health. Talk to your pharmacist for more details.

If you’re suffering from any liver disease, telling your doctor must be the first thing to do before using this medication. If you’re taking Robaxin regularly, it may make you feel dizzy or make your vision blurry.

Do not drive or use machinery when you consume this medicine or do not do such activity that needs alertness until you can do it safely. Avoid alcohol or marijuana after or before taking Robaxin; if you take it, get ready to visit your doctor.

Zanaflex Precautions

Zanaflex Precautions

Precautions are almost similar to Robaxin; if you’re allergic to Zanaflex, consult your doctor and get the required information about the drug. If you’re suffering from any issue regarding low blood pressure, kidney disease, or liver disease, then ask your doctor for any help regarding the consumption of Zanaflex.

If you’re having any tooth surgery or body surgery, then tell your doctor or dentist about all the products you are taking, which may include herbal products, prescription drugs, and non-prescription drugs.

Studies have seen that side effects of this drug are more affected to the older adults as they are more sensitive to it, especially the effects may include drowsiness and dizziness, which may lead to a risk of falling.


Both Robaxin and Zanaflex are muscle relaxants and are prescribed by the doctors in proper proportion. These drugs may damage your health after being taken in excess proportion, so be aware of this condition and be in contact with your doctor for any issues.


  1. Poudel, R.R. and Kafle, N.K., 2015. Tizanidine-induced acute severe cystitis in a female taking famotidine. Clinical pharmacology: advances and applications7, p.83. Available at: Accessed on 01/10/2021
  2. Forsyth, H.F., 1958. Methocarbamol (Robaxin) in orthopedic conditions: Preliminary report of one hundred cases. Journal of the American Medical Association167(2), pp.163-168. Available at: Accessed on 01/10/2021
  3. McLain, D., 2002. An open label dose finding trial of Tizanidine [Zanaflex™] for treatment of fibromyalgia. Journal of Musculoskeletal Pain10(4), pp.7-18. Available at: Accessed on 01/10/2021
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