Prescription medication · Muscle Relaxant

cyclobenzaprine

Name: cyclobenzaprine - FDA Drug Safety & Adverse Event Data
Creator: PlainMeds
License: https://creativecommons.org/publicdomain/zero/1.0/

Also sold as Flexeril, Amrix. This medicine treats muscle spasms caused by painful conditions.

Compiled by PlainMeds, Drug Information Editorial Process

Data updated 2026-05-15

47,426
FDA reportsOften reported: 17
InteractionsSeveral interactions: $0.02
Generic price (NADAC)

What the data shows

cyclobenzaprine (Flexeril) is a prescription Muscle Relaxant, reported at a middle-of-the-pack volume (47,426 FDA reports), with 17 documented drug interactions.

Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.

cyclobenzaprine (Flexeril) is a prescription Muscle Relaxant. This medicine treats muscle spasms caused by painful conditions.

Cyclobenzaprine is a muscle relaxant. It helps relieve muscle spasms and pain.

Verify with FDA → · CMS NADAC pricing →

Drug Pricing (NADAC)

Generic Price

$0.02/unit

Generic Available

Yes (13 manufacturers)

Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →

View Alternatives → Compare with Another Drug → Full Side Effects Report →

What it does

This medicine treats muscle spasms caused by painful conditions.

Common side effects

Drowsiness, Dry mouth, Fatigue

Key warnings

You should not take this medicine if you are allergic to any of its ingredients.

The sections below are summarized in plain English from cyclobenzaprine's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.

How It Works

Cyclobenzaprine works in the brain and spinal cord to relax your muscles. It reduces muscle spasms, which helps to relieve pain and improve movement. It does not directly work on the muscles themselves.

Side Effects (from patient reports)

Based on 47,426 FDA adverse event reports.

Pain

4,871
Fatigue

3,808
Nausea

3,303
Headache

3,292
Chronic Kidney Disease

2,749
Diarrhoea

2,426
Fall

2,334
Arthralgia

2,325
Toxicity To Various Agents

2,289
Dyspnoea

2,099

What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.

Reports over time

Adverse-event reports filed for cyclobenzaprine each year to the FDA Adverse Event Reporting System (FAERS).

Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.

Where cyclobenzaprine sits

cyclobenzaprine has more FDA adverse-event reports than 72% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.

fewest reports most reports

Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is cyclobenzaprine; the line is the median (50th percentile).

FDA Adverse Event Report Analysis

Detailed analysis of 47,426 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2003–2025.

Total Reports

47,426

Reports Mentioning Death

6,863

14.5% of reports — not proof of cause

Hospitalization Reports

13,293

Top Indication

Product Used For Unknown Indication

Gender Distribution

Female 31,623 (72%)

Male 12,204 (28%)

Age Distribution

0–17 446

18–44 7,427

45–64 15,065

65–74 4,969

75+ 2,540

Most Reported Adverse Reactions (FAERS)

#	Reaction	Reports
1	PAIN	4,871
2	FATIGUE	3,808
4	NAUSEA	3,303
5	HEADACHE	3,292
6	CHRONIC KIDNEY DISEASE	2,749
8	DIARRHOEA	2,426
9	FALL	2,334
10	ARTHRALGIA	2,325
11	TOXICITY TO VARIOUS AGENTS	2,289
12	DYSPNOEA	2,099
13	CONSTIPATION	2,064
14	BACK PAIN	2,048
15	COMPLETED SUICIDE	1,953
16	DIZZINESS	1,936
17	ANXIETY	1,929

Reactions in Death Reports

COMPLETED SUICIDE 1,948

DEATH 1,521

TOXICITY TO VARIOUS AGENTS 1,465

DRUG ABUSE 919

CARDIO-RESPIRATORY ARREST 478

CARDIAC ARREST 427

HYPERTENSION 376

RESPIRATORY ARREST 364

OVERDOSE 331

PAIN 322

Reactions in Hospitalization Reports

PAIN 1,737

FALL 1,481

NAUSEA 1,120

DYSPNOEA 1,111

PNEUMONIA 1,098

HYPOTENSION 1,052

TOXICITY TO VARIOUS AGENTS 1,049

FATIGUE 1,036

CONSTIPATION 990

HEADACHE 844

Source: FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation

Serious Warnings

You should not take this medicine if you are allergic to any of its ingredients. You should not take this medicine if you are taking a monoamine oxidase (MAO) inhibitor or have taken one in the past 14 days. Taking cyclobenzaprine with an MAO inhibitor can cause serious problems, including seizures and death. Also, do not take it if you have heart problems or an overactive thyroid.

Known Drug Interactions

moderate clozapine

Anticholinergic Drugs Concomitant treatment with clozapine and other drugs with anticholinergic activity (e.g., benztropine, cyclobenzaprine, diphenhydramine) can increase the risk for anticholinergic toxicity and severe gastrointestinal adverse reactions related to hypomotility.

Mechanism: Both drugs have similar side effects that can slow down your digestive system and cause confusion or dry mouth. Combining them makes these side effects much more likely and can lead to severe constipation or toxicity.

moderate tapentadol

Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue). Due to the risk of respiratory depression with concomitant use of skeletal muscle relaxants and...

Mechanism: Taking these drugs together increases the risk of dangerous slowing of your breathing. They can also cause a serious buildup of a brain chemical called serotonin.

moderate tranylcypromine

Product Clinical Comment on Concomitant Use [See Contraindications (4.1)] ; Predominant Effect/Risk [Hypertensive Reaction (HR) [See Warnings and Precautions (5.3)] ; or Serotonin Syndrome (SS) [See Warnings and Precautions (5.7)] ] Altretamine Use with caution If not otherwise specified in this table, consider avoiding concomitant use (see also information on medication-free intervals , use agent at the lowest appropriate dose, monitor for effects of the interaction, advise the patient to report potential effects, and be prepared to discontinue the agent and treat effects of the...

Mechanism: Taking these drugs together can lead to a life-threatening reaction or a sudden, very high increase in blood pressure.

minor acetaminophen/oxycodone

Serotonergic Drugs The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system, such as selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), tryptans, 5-HT3 receptor antagonists, drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), and monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and...

Mechanism: Both drugs increase serotonin levels in the brain, which can cause a serious reaction called serotonin syndrome.

minor buprenorphine

Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue).

Mechanism: Both drugs increase serotonin levels in the brain, which can cause a serious and potentially dangerous reaction.

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This is a plain-language summary of FDA-label interaction records and does not provide individual medication-combination directions.

Common Questions

Can I drive while taking this medicine?

This medicine can cause drowsiness, so be careful driving or operating machinery until you know how it affects you.

Can I drink alcohol while taking this medicine?

Drinking alcohol can increase the drowsiness caused by this medicine. Avoid alcohol while taking cyclobenzaprine.

How long does it take for this medicine to work?

You should start to feel some relief from your muscle spasms within a few days.

Can I take this medicine with other medicines?

Talk to your doctor or pharmacist before taking this medicine with other medicines. Cyclobenzaprine can interact with other medicines, especially MAO inhibitors.

What should I do if I have side effects?

Tell your doctor if you have any side effects that bother you or do not go away.

Can I stop taking this medicine suddenly?

Talk to your doctor before stopping this medicine. Stopping suddenly may cause withdrawal symptoms.

Is cyclobenzaprine a painkiller?

No, cyclobenzaprine is a muscle relaxant. It helps to relieve muscle spasms, which can reduce pain.

Can I take cyclobenzaprine long term?

Cyclobenzaprine is only recommended for short-term use (up to 2 or 3 weeks).

What do the different colored pills mean?

Cyclobenzaprine tablets come in different strengths and colors. The color does not affect how the medicine works.

Can I crush or split the tablets?

Ask your pharmacist or doctor if it is okay to crush or split your specific tablet formulation.

What are the common side effects of cyclobenzaprine?

The registry lists Drowsiness, Dry mouth, Fatigue, Headache among the most-reported FAERS reaction terms for cyclobenzaprine. The compiled record contains 47,426 FDA adverse-event reports. These counts are not an individual symptom assessment.

Does cyclobenzaprine interact with other medications?

The registry has 17 documented interaction rows for cyclobenzaprine. Notable source-record pairings include clozapine, tapentadol, tranylcypromine. These rows are not a complete medication review.

What drug class is cyclobenzaprine?

cyclobenzaprine belongs to the Muscle Relaxant drug class. It requires a prescription (Rx). This medicine treats muscle spasms caused by painful conditions.

What pregnancy or breastfeeding source fields are listed for cyclobenzaprine?

The FDA label for cyclobenzaprine contains product-specific pregnancy or breastfeeding language. PlainMeds does not apply that source text to an individual.

Other drugs grouped near cyclobenzaprine - same-class peers and common alternatives.

baclofen

Lioresal, Gablofen

Baclofen is a muscle relaxant.