Taking Cyclobenzaprine With Gabapentin

In our latest question and answer, the pharmacist discusses the potential interaction between cyclobenzaprine and gabapentin.

Apr 19, 2018

Theo asked

I have small cell AGGRESSIVE carcinoma, and also RLS. Am unable to sleep due to RLS, so was wondering what would happen if took both Flexeril and Gabapentin?


Taking cyclobenzaprine and gabapentin together may cause an increase in central nervous system (CNS) side effects. These side effects can include:

  • Problems with coordination and/or balance
  • Confusion
  • Drowsiness
  • Weakness
  • Respiratory depression

For most patients, this interaction is something that can be monitored. However, for a patient with small cell carcinoma, this interaction may pose a problem, especially with the potential for respiratory depression. Not knowing the particulars of your current health condition, it would be best to check with your current doctor. If these are drugs you have taken before without too many side effects and your health, particularly your lung function, is stable, your doctor may feel it is appropriate therapy for you to take both drugs at the same time. Below is some more information on both drugs.

Flexeril (Cyclobenzaprine)

Flexeril (Cyclobenzaprine) is a skeletal muscle relaxer. It is typically used for the short-term relief of muscle spasms. The most common side effects are:

  • Drowsiness
  • Dizziness
  • Dry mouth
  • Fatigue
  • Confusion/decreased mental acuity
  • Irritability
  • Nervousness

Patients should be cautious driving or operating machinery until the effects of the drug are known. Patients should also be cautious when combining with other medications that can cause the CNS side effects of drowsiness or respiratory depression.

Neurontin (Gabapentin)

While gabapentin is classified as an anticonvulsant used in the treatment of seizures and postherpetic neuralgia (complication of shingles), it is often used for off-label treatment of other conditions. Off-label use is when a drug is used for an unapproved indication and has not been approved by the FDA for that indication. Off-label uses of gabapentin include:

  • Treatment of alcohol dependence
  • Alcohol withdrawal
  • Chronic cough
  • Diabetic neuropathy
  • Fibromyalgia
  • Hiccups
  • Hot flashes
  • Neuropathic pain
  • Restless legs syndrome (RLS)
  • Social anxiety disorder
  • Chronic itching

The most common side effects of Gabapentin include:

  • Dizziness
  • Coordination problems
  • Fatigue
  • Nausea/vomiting
  • Diarrhea
  • Tremor
  • Dry mouth
  • Constipation
  • Headache

Taking Flexeril (Cyclobenzaprine) and Gabapentin together may result in an increase of CNS side effects like drowsiness, respiratory depression, confusion, balance problems or weakness. Patients who may have health problems, like small cell carcinoma, that could put them at an increased risk of side effects should check with their doctor before taking both drugs together.

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