Zanaflex (Tizanidine) With Soma (Carisoprodol) Interaction

In our latest question and answer, the pharmacist discusses the potential interaction between Soma (carisoprodol) and Zanaflex (tizanidine).

Jul 29, 2018

NewtonT asked

I have Parkinson's disease and dystonia. I suffer from horrible muscle spasms, I have tried every muscle relaxer available and carisoprodol works best with little to no sedation. However I am only allowed to take 4-350mg tabs 4 times a day. Some days, the medicine just doesn't cut it so instead of taking more carisoprodol I will take a small dose of tizanidine. I have checked all over and see that there is either no interaction or a moderate interaction. Is this OK to do?


There is an interaction between Zanaflex (tizanidine) and Soma (carisoprodol) in that they can have additive side effects, like sedation and cognitive impairment, when used together. Both are actually classified as muscle relaxants and therefore, it is considered a 'duplicate therapy' to be on both.

Nevertheless, even though Zanaflex and Soma are both muscle relaxants, they do have slightly different mechanisms of action and it is certainly feasible that using both could confer additions benefits. However, you should speak with your doctor first before using both.

What Is Soma (Carisoprodol)?

Soma (Carisoprodol) is a centrally acting muscle relaxant, meaning that it works directly in the central nervous system (CNS). The exact mechanism of action isn't clear but it appears to interrupt neuronal communication within spinal cord. It is well known to cause CNS depression, which produces sedation and alters perception of pain.

In addition to its muscle relaxant properties, Soma also acts as a mild anxiolytic (i.e. anti-anxiety) and sedative agent. This is because one of the metabolites of Soma metabolism is meprobamate, a commercially available drug used for anxiety.

Soma can cause euphoria and there is a significant risk of withdrawal, tolerance, and dependence with extended use. Due to these characteristics, it is classified as a Schedule IV controlled substance.

What Is Zanaflex (Tizanidine)?

Unlike Soma, Zanaflex (tizanidine) is not considered a CNS depressant, but works as an alpha2-adrenergic agonist. This actions significantly reduces muscle tone and frequency of spasms. While Soma is generally used more for painful musculoskeletal conditions, Zanaflex is more helpful for the management of muscle spasticity.

Like Soma, Zanaflex can cause considerable sedation but is not thought to carry any risk for dependence. However, if you take Zanaflex for an extended period of time, it is recommended to be slowly tapered as abrupt withdrawal can actually cause high blood pressure and increased heart rate.

Some additional notes about Zanaflex include:

  • It has a short duration of action, around 3 to 6 hours.
  • Be sure to take it consistently with or without food as food significantly affects absorption.

Difference Between Soma And Zanaflex

To sum up the differences between Soma and Zanaflex:

  • Soma (carisoprodol) is a centrally acting muscle relaxant, working directly in the central nervous system.
  • Zanaflex (tizanidine) work as an alpha2-adrenergic agonist.
  • Soma is generally more helpful in reducing painful musculoskeletal conditions while Zanaflex is more helpful in reducing muscle spasticity.
  • Soma is a Schedule IV controlled substance, and can cause euphoria and dependence. Zanaflex is not a controlled substance.

Taking Soma With Zanaflex

As both Soma and Zanaflex are muscle relaxants, use together generally isn't recommended. However, they do work differently and can have different effects on an individual. In terms of an interaction, they can certainly cause additive sedation, drowsiness and increase the risk of mental confusion. Using both together can also increase your risk of rebound spasticity upon discontinuation.

If both drugs were not prescribed to you for use together, speak to your doctor about the most effective therapy options for your situation.

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