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Tizanidine: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Feb 23, 2021.

1. How it works

  • Tizanidine may be used to treat spasticity associated with a brain or spinal injury.
  • Tizanidine works by a central mechanism (this means it acts in the brain) but experts are not sure exactly how it works to reduce muscle tone and spasm, but suggest it may be due to tizanidine increasing presynaptic inhibition of the nerves that supply the muscles. Tizanidine works more on polysynaptic pathways rather than monosynaptic spinal reflexes. Tizanidine relaxes muscles by dampening down nerve impulses that are sent from spasming muscles along nerve fibers to the brain.
  • Tizanidine belongs to the class of medicines known as central alpha-2-adrenergic agonists. It may also be called a centrally-acting muscle relaxant.

2. Upsides

  • May be used to reduce muscle spasms that are associated with cerebral (brain) or spinal injury.
  • May be used alone or together with other treatments for muscle spasm, such as baclofen.
  • Effective at relaxing muscles (reduces muscle spasms).
  • No direct effects on skeletal muscle fibers.
  • May improve pain associated with muscle spasm.
  • May be used on an as-needed basis.
  • Despite being structurally related to clonidine, tizanidine has only 1/10th to 1/50th of clonidine's antihypertensive effect which means it is less likely to lower blood pressure than clonidine.
  • Tizanidine is usually started as a dosage of 2mg to 4mg to minimize the risk of side effects; however, dosages less than 8mg have been shown to be ineffective in clinical trials. The dosage should be increased by 2-4mg daily for 2 to 4 weeks until the best effects are seen.
  • No dosage adjustments are needed for liver disease.
  • Generic tizanidine is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Low blood pressure, drowsiness, dizziness, energy loss, and a dry mouth.
  • Has been associated with hallucinations and rarely psychosis in approximately 3% of people.
  • The dosage of tizanidine needs to be individualized according to a person's requirements and response.
  • May not be suitable for people that rely on spasticity to sustain their posture and balance.
  • May cause a drop in blood pressure when going from a sitting or lying down position to standing. This may increase the risk of falls.
  • May affect a person's ability to drive or operate machinery. Alcohol should be avoided.
  • May cause withdrawal symptoms such as high blood pressure and a fast heartbeat if stopped abruptly after regular extended dosing (decrease dose slowly under a doctor's advice). Withdraw tizanidine slowly. Decrease by about 2mg to 4mg per day.
  • Seniors may be more susceptible to the side effects of tizanidine.
  • Tizanidine may cause allergic reactions in some people, such as anaphylaxis and urticaria.
  • May interact with a number of other drugs including those metabolized by hepatic enzymes CYP1A2 (such as fluvoxamine, ciprofloxacin, some antiarrhythmics), and oral contraceptives. Alcohol increases the peak concentration of tizanidine and also the likelihood of side effects.
  • Liver enzymes (specifically aminotransferase) should be monitored when starting treatment, when clinically indicated, and for at least one month after the maximum dosage is achieved.
  • The different dosage forms of tizanidine (for example, the tablets vs capsules) and modification of the administration of tizanidine (for example swallowing the capsules whole vs opening them up and sprinkling them on applesauce) may cause clinically important differences in effect, such as more side effects or a more rapid onset of activity.
  • Needs to be given every 6 to 8 hours. Maximum single dose is 16mg and maximum total daily dose is 36mg in 24 hours.
  • The safety and effectiveness of tizanidine has not been established for people aged under 18 years.
  • Lower total daily dosages may be necessary with kidney disease. Increase individual dosages if higher dosages are needed rather than increasing dosage frequency.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Tizanidine relieves muscle spasms but may cause sleepiness, a drop in blood pressure, and sedation. The dosage should be individualized and because it only lasts for a short time in the body, can be taken on an as needed basis. Monitoring of liver enzymes is required.

5. Tips

  • Capsules may be opened and the contents sprinkled on food.
  • Taking with food increases absorption by 20% but slows time for effect. Can be taken with or without food, but should be dosed consistently (either with or without food).
  • Tizanidine is relatively short-acting; therefore it should be taken at times when relief of spasticity is the most important (such as before activities of daily living).
  • Take tizanidine exactly as directed. Do not increase the dosage without your doctor's advice. Tizanidine tablets and capsules are not directly interchangeable; a dosage adjustment may be necessary (talk with your doctor).
  • Be careful when going from sitting or lying down position to standing as tizanidine may increase your risk of falls. Remove any fall hazards (such as loose rugs) from your home.
  • Seek immediate medical advice if you experience any worrying side effects including hallucinations, fainting, sleepiness, or allergic-type reactions.
  • Do not stop taking tizanidine suddenly without your doctor's advice as high blood pressure and a fast heartbeat may result.
  • Effects are dose-related (the bigger the dose, the stronger the effect, but the more noticeable any side effects are).
  • Tizanidine can make you sleepy. The risk is greater if you also take other drugs, such as benzodiazepines, or sleeping pills. Do not drink any alcohol while taking tizanidine.
  • Do not take any other medication, including medicines brought over-the-counter, in addition to tizanidine, without first checking with your doctor or pharmacist first to make sure they are compatible.

6. Response and effectiveness

  • The effects of tizanidine peak within 1-2 hours and start to wear off within 3 to 6 hours. Because of this short duration of effect, tizanidine may be dosed on an "as needed" basis during times when muscle spasms are at their most severe.

7. Interactions

Medicines that interact with tizanidine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with tizanidine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with tizanidine include:

  • acyclovir
  • amiodarone
  • anti-anxiety medications
  • anticonvulsants
  • antidepressants, such as amitriptyline, imipramine, nortriptyline
  • antihistamines that cause sedation, such as diphenhydramine
  • azelastine
  • chlormethiazole
  • ciprofloxacin
  • dronedarone
  • duloxetine
  • fluvoxamine
  • HIV medications such as saquinavir
  • medications that lower blood pressure, such as ACE inhibitors (eg, enalapril), barbiturates, beta-blockers (such as atenolol), or calcium channel antagonists (such as diltiazem)
  • medicines that inhibit CYP1A2 enzymes such as cimetidine or rifampin
  • metoclopramide
  • opioid analgesics such as oxycodone and morphine
  • other muscle relaxants such as methocarbamol
  • pimozide
  • sleeping pills, such as zolpidem
  • some chemotherapy treatments
  • some medications used to treat mental illness, such as clozapine and thioridazine
  • smoked tobacco
  • treatments for erectile dysfunction, such as sildenafil or tadalafil
  • topiramate
  • zolpidem.

Alcohol may worsen the side effects of tizanidine such as drowsiness and dizziness.

Note that this list is not all-inclusive and includes only common medications that may interact with tizanidine. You should refer to the prescribing information for tizanidine for a complete list of interactions.

References

Tizanidine. Revised 10/2020. Drugs.com. https://www.drugs.com/ppa/tizanidine.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use tizanidine only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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