Cyclobenzaprine - Dosage | Adverse effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Cyclobenzaprine is a chemical substance (drug) that acts by relaxing the muscles and belongs to a group of drugs called centrally-acting muscle relaxants. It has a similar chemical structure as tricyclic antidepressants but the way it works is much more complex. It works by blocking the broadcast of signals (pain) from the nerve to the brain and thereby alleviates pain. So far, it has mostly been tested on animals. It is used in the following conditions:

  • Relief of the symptoms of muscle spasm (cramps)
  • Relief of the symptoms of a pulled muscle
  • Relief of the symptoms of muscle injuries
  • Fibromialgia1

The most common indication is a pain in the lower back. Although some authors argue that this medicine can also be used for the treatment of migraine and insomnia, there are no clinical studies that confirm the beneficial effect of this drug in these situations.


Cyclobenzaprine can cause tachyarrhythmia2, and should not be used in patients who already have problems with heart rhythm.

Cases of Cyclobenzaprine-induced rhabdomyolysis have been reported, and this drug should not be used in patients who already have muscle damage/muscle disorder or take other medicines that can cause rhabdomyolysis (e.g. drugs that lower cholesterol).

Cyclobenzaprine can cause respiratory failure in approximately 3% of patients, so be sure to tell your doctor if you have a lung disease.

Due to its anticholinergic effects, it should be avoided in the following patients:

  • Patients who have enlarged prostate
  • Patients who have elevated intraocular pressure

The anticholinergic effects of this drug can lead to extreme drying of the mouth. You can use lip balm to alleviate this side effect. If this side effect does not stop after three weeks, inform your doctor.

As it has shown a moderate inhibitory effect on the serotonin reuptake and considering its similar chemical structure with tricyclic antidepressants, it should never be used simultaneously with other anti-depressants which are known as MAO inhibitors. If you are taking or have taken any of the MAO inhibitors (e.g. selegiline, rasagiline, isocarboxazid and others) in the past two weeks, then you should not start taking Cyclobenzaprine.

Cyclobenzaprine, pregnancy and lactation

There is one case in which the use of Cyclobenzaprine in the last trimester of pregnancy led to increased pressure in the pulmonary artery which caused respiratory insufficiency in the newborn.3 Other adverse effects in newborns have not been reported. Consult your doctor if you are pregnant or breastfeeding.

Do not breastfeed your baby while you are on treatment with this drug.


The recommended dose is 15-30 mg daily for 14 days.

The dose should be reduced in elderly patients and in patients with hepatic impairment.

Application longer than 14 days may lead to withdrawal syndrome after stopping the drug. Your doctor will explain how to gradually reduce the dosage of the drug before you completely stop using it.

Swallow the capsule whole, with sufficient liquid.


About 700 interaction of Cyclobenzaprine with other drugs is known, of which about 80 are classified as significant.

Significant interactions of Cyclobenzaprine with other drugs are listed in the table below:

Drugs that may interact with Cyclobenzaprine Reason why concomitant use is not recommended
5-hydroxytryptophan and tryptophan
Amoxapine and doxepin Increased risk of serotonin syndrome (a serious, potential life-threatening disorder)
MAO inhibitors
Amitriptyline, chlorimipramine and other tricyclic antidepressants
Buprenorphine Increased risk of respiratory failure
Potassium preparations Increased risk of adverse effects on the digestive tract
Propoxyphene Increased risk of side effects (e.g. drowsiness, confusion, and impaired thinking)

This table does not contain all known interactions. Tell your doctor if you are taking any other medicines.

Adverse effects

Cyclobenzaprine may cause the following side effects:

  • Drowsiness
  • Confusion
  • Blurred vision
  • Dry mouth
  • Urinary retention and trouble urinating
  • Hallucinations
  • Unusual dreams
  • Depression
  • Seizures
  • Respiratory distress
  • Restlessness and agitation
  • Digestive disorders
  • Serotonin syndrome
  • Tachyarrhythmia
  • Vasodilation

Tell your doctor if you notice any other side effects.


  1. NCBI link 1
  2. NCBI link 2
  3. NCBI link 3

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