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Cyclobenzaprine Side Effects

The most commonly reported side effects of cyclobenzaprine include pain, fatigue, and nausea, based on 79,839 FDA adverse event reports from 2004 to 2025. 6.2% of reports found the drug to be ineffective.

Cyclobenzaprine side effects

Percentages show how often each reaction appears relative to total reports for cyclobenzaprine.

1
Pain8.2%6,530
2
Fatigue6.9%5,511
3
Drug Ineffective6.2%4,919
4
Nausea5.9%4,707
5
Headache5.7%4,583
6
Off Label Use4.5%3,553
7
Diarrhoea4.4%3,547
8
Arthralgia4.2%3,324
9
Chronic Kidney Disease4.1%3,306
10
Fall4.1%3,263
11
Dyspnoea3.6%2,882
12
Back Pain3.6%2,863
13
Dizziness3.5%2,823
14
Anxiety3.3%2,622
15
Vomiting3.2%2,591

These are voluntary reports and do not establish that cyclobenzaprine caused these reactions.

Report severity

64.9%Serious51,791 reports
28.3%Hospitalizations22,569 reports
11.4%Fatal9,067 reports

Seriousness is determined by the reporter, not by OpenClaim.

Cyclobenzaprine drug interactions

Other drugs that appear in adverse event reports alongside cyclobenzaprine. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Adalimumab6.7%5,329
2
Sodium-oxybate5.0%4,004
3
Omeprazole5.0%3,993
4
Lenalidomide4.6%3,643
5
Acetaminophen4.5%3,597
6
Esomeprazole4.1%3,288
7
Pantoprazole-sodium4.1%3,286
8
Oxycodone3.7%2,920
9
Etanercept3.6%2,895
10
Gabapentin3.2%2,589
11
Pregabalin3.2%2,520
12
Quetiapine-fumarate2.3%1,847
13
Lansoprazole2.3%1,841
14
Rituximab2.2%1,754
15
Tocilizumab2.2%1,754

Taken alongside

1
Acetaminophen29.9%23,892
2
Gabapentin20.3%16,239
3
Ergocalciferol18.5%14,777
4
Aspirin16.3%13,051
5
Albuterol16.3%13,042
6
Hydrocodone14.9%11,881
7
Omeprazole14.7%11,737
8
Levothyroxine-sodium14.3%11,433
9
Oxycodone14.1%11,236
10
Ibuprofen13.7%10,947
11
Fluticasone12.9%10,286
12
Tramadol-hydrochloride12.8%10,227
13
Prednisone12.4%9,880
14
Lisinopril11.6%9,271
15
Furosemide11.2%8,921

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports cyclobenzaprine side effects

68.8% of cyclobenzaprine adverse event reports involve female patients and 25.1% involve male patients. The largest age group is adult at 76%. These figures reflect who reports side effects, not underlying risk.

Sex

Female68.8%
Male25.1%
Unknown6.1%

Age group

< 20.2%
2–11<0.1%
12–170.8%
18–6476.0%
65+22.9%

What is cyclobenzaprine used for

Conditions and purposes for which patients were taking cyclobenzaprine when the adverse event was reported.

Abdominal PainAbdominal Pain UpperAbdominal RigidityAccident At WorkAccidental ExposureAccidental OverdoseAcneAcute Respiratory FailureAdnexa Uteri PainAdverse EventAffective DisorderAgitationAlopeciaAmenorrhoeaAnaesthesia

Showing 15 of 678 indications

Cyclobenzaprine brand names and reporting trend

Cyclobenzaprine is sold under the brand name Flexeril.

Brand names

Flexeril2,596

Quarterly reports (20042025)

20052010201520202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking cyclobenzaprine with another medication?

Ask OpenClaim about your specific drug combination. Get a sourced report using FDA data, drug labels, and medical literature.