Can Muscle Relaxers Cause Constipation? 5 Muscle Relaxers Side Effects

Last Updated: June 18, 2024

Dr. Norman Chazin Reviewed by Dr. Norman Chazin
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Muscle relaxers are prescription drugs that temporarily relieve pain, muscle spasms, and spasticity by acting on the central nervous system.

Even though muscle relaxants were initially approved for short-term treatment, skeletal muscle relaxants are now frequently used in the U.S. for chronic pain and other conditions despite limited evidence of their long-term effectiveness or safety.

While these medications might seem innocuous, side effects of muscle relaxers can be significant, especially with prolonged use or in combination with painkillers. Do muscle relaxers lower blood pressure, cause constipation, or induce drowsiness? Read on to understand the potential risks of muscle relaxant use.

Muscle Relaxers Overview

Muscle relaxers, such as cyclobenzaprine (Flexeril), methocarbamol (Robaxin), and carisoprodol (Soma), are a class of prescription medications that act on the central nervous system to alleviate muscle spasms, pain and stiffness.

These medications are particularly useful in managing acute musculoskeletal conditions and are often used in tandem with rest and physical therapy. Despite their benefits, muscle relaxers can make people feel dizzy and sleepy and even cause constipation.

In fact, muscle relaxers’ side effects can become significantly serious, particularly in older adults. Let’s review these adverse effects:

What Are The Side Effects Of Muscle Relaxers?

Muscle relaxant relief may come with a set of undesired adverse effects. From common problems like drowsiness and constipation to more severe concerns such as dependency and overdose, here we provide a list:


If you have noticed changes in your bowel during muscle relaxant treatment, you may have wondered: Do muscle relaxers cause constipation? The answer is yes.

Some muscle relaxers, such as cyclobenzaprine and baclofen, have anticholinergic effects. Anticholinergics block the action of acetylcholine, a neurotransmitter involved in muscle contraction and movement. By inhibiting acetylcholine, these drugs reduce the contractions of the intestinal muscles, making it harder for the bowel to move waste through the digestive system.

To manage muscle relaxers’ constipation, you can:

  • Eat high-fiber foods to add bulk to stool and promote regular bowel movements.
  • Consider fiber supplements such as psyllium (Metamucil) if dietary changes are insufficient.
  • Drink enough water throughout the day to help keep the stool soft and easier to pass.
  • Probiotics can help maintain a healthy balance of gut bacteria, improving digestion and regularity.
  • Discuss with your healthcare provider using OTC medication like mild laxatives (i.e., MiraLAX, Colace).

Dry Mouth

Dry mouth, or xerostomia, is another side effect of muscle relaxers, particularly those with anticholinergic properties like cyclobenzaprine and baclofen. Anticholinergic medications interrupt the neural stimulation of saliva secretion, reducing saliva flow and leading to hyposalivation.

Here are some strategies to help manage this muscle relaxant side effect:

  • Drink water frequently throughout the day to keep your mouth moist.
  • Limit intake of caffeine, alcohol and tobacco, as they can worsen dry mouth.
  • Use an alcohol-free mouthwash designed for dry mouth to avoid further irritation.
  • Over-the-counter saliva substitutes or oral moisturizers can provide temporary relief.
  • In severe cases, your doctor may prescribe medications that stimulate saliva production.

Hypotension or Low Blood Pressure

Muscle relaxers act on the central nervous system to reduce muscle tone and alleviate spasms. They can also relax blood vessels, decreasing vascular resistance and causing a decrease in blood pressure.

Do muscle relaxers raise blood pressure? No, muscle relaxers can cause hypotension. In a study, tizanidine in conjunction with strong CYP1A2 inhibitors, such as Fluvoxamine, Ciprofloxacin or Mexiletine, significantly increased severe hypotensive episodes.

Healthcare providers should avoid co-prescribing tizanidine with CYP1A2 inhibitors, especially in patients with multiple health conditions or those taking three or more antihypertensive medications. To manage low blood pressure due to muscle relaxers:

  • Regularly check your blood pressure at home when starting muscle relaxer treatment.
  • Drink plenty of fluids to help maintain blood volume and pressure.
  • Report any significant drops in blood pressure to your healthcare provider.
  • Avoid alcohol consumption, which can further lower blood pressure.
  • Discuss any symptoms of low blood pressure, such as dizziness or fainting, with your doctor.

Allergic Reactions

Eperisone and afloqualone are oral muscle relaxants that improve circulation and suppress pain reflexes.

They are often prescribed in combination with painkillers like nonsteroidal anti-inflammatory drugs (NSAIDs) for enhanced pain relief. Despite their benefits, there are reports that these drugs can cause severe allergic reactions, including anaphylaxis, which is a life-threatening condition that requires immediate medical attention.

  • Symptoms can include rash, itching, swelling, dizziness, and difficulty breathing.
  • Anaphylaxis symptoms include throat and tongue swelling, difficulty breathing, and loss of consciousness.
  • If an allergic reaction occurs, stop taking the muscle relaxant immediately and seek medical attention.
  • After experiencing an allergic reaction, discuss alternative treatments with your doctor.
  • Inform your doctor of any known allergies or previous reactions to medications.


Dizziness is a common side effect of muscle relaxers. These medications act on the brain, slowing down the central nervous system, which can lead to dizziness.

This effect is particularly noticeable when standing up or moving quickly, and it can make it difficult to control your hands and feet. This dizziness can significantly increase the risk of falls, which can be particularly dangerous for older adults.

If you are feeling dizzy while taking muscle relaxants:

  • Rise slowly and hold onto something stable to prevent falls.
  • Avoid sudden movements and take your time when standing up to reduce dizziness.
  • Refrain from consuming alcohol, as it can enhance the dizziness caused by muscle relaxers.
  • Avoid the combination of painkillers and muscle relaxants, as it can worsen the side effects of muscle relaxers.
  • Avoid tasks that require motor skills or balance until you feel better.
  • If dizziness persists or worsens, talk to your healthcare provider.

Muscle Relaxers Side Effects

Long-Term Muscle Relaxers Side Effects

Remember that these medications are intended for short-term use only. Experts generally recommend limiting the use of these drugs to a maximum of three weeks because they have not proven effective for muscle spasms beyond that duration.

Extended use can lead to serious long-term side effects of muscle relaxers, such as:

  • Tolerance
  • Impaired thinking and functioning
  • Blurred vision
  • Liver damage
  • Muscle weakness
  • Abuse, drug addiction, and overdose

Muscle Relaxers Side Effects − Bottom Line

Muscle relaxants can be controversial alternatives for nonspecific back pain, muscle spasms, or spasticity due to the risks of adverse effects. Although they are not recommended as primary treatment, 18.5% of patients receive them as initial therapy.

Given the current use frequency of muscle relaxers, perhaps the most dangerous risk associated with these drugs is addiction. The sedative effects of muscle relaxers that cause relaxation and numbness may be the primary reason for their abuse potential.

It is crucial for healthcare providers to be well-informed about muscle relaxants use in the U.S. to prevent further worsening patient health outcomes. Prolonged use can lead to physical dependence, and individuals with addiction to this medication may require addiction treatment, including drug detox and rehabilitation programs.

People Also Ask

Do muscle relaxers make you last longer in bed?

No, muscle relaxers do not generally affect sexual performance by itself or increase stamina in bed.

Do muscle relaxers make you constipated?

Yes, muscle relaxers can cause constipation. They relax the muscles in the gut, slowing down bowel movements, and some have anticholinergic properties that further reduce gut motility.

Do muscle relaxers cause weight gain?

Weight gain is not a common side effect of muscle relaxers. However, their sedative effects can reduce physical activity, potentially leading to weight gain.

Page Sources

  1. Jackson, K. C., & Argoff, C. E. (2008). Skeletal Muscle Relaxants. Raj's Practical Management of Pain (Fourth Edition), 693-698.
  2. Long-term use of muscle relaxants has skyrocketed since 2005 - Penn Medicine. (n.d.).
  3. Harvard Health. (2019, October 22). What to do when medication makes you constipated.
  4. Arany et al. (2021). Anticholinergic medication: Related dry mouth and effects on the salivary glands. Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology, 132(6), 662–670.
  5. Tizanidine, a Frequently Used Muscle Relaxant, Is Associated with Severe Hypotension: Role of Cytochrome P450 1A2 Inhibition in Routine Clinical Practice - ACR Meeting Abstracts. (2018, August 24). ACR Meeting Abstracts.
  6. Hur, G., Hwang, E. K., Moon, J., Ye, Y., Shim, J., Park, H., & Kang, K. (2012). Oral muscle relaxant may induce immediate allergic reactions. Yonsei Medical Journal/Yonsei Medical Journal, 53(4), 863.
  7. Witenko, C., et al. (2014, June 1). Considerations for the appropriate use of skeletal muscle relaxants for the management of acute low back pain. PubMed Central (PMC).
Retrieved on June 18, 2024.

Published on: August 14th, 2019

Updated on: June 18th, 2024


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