What the label lists and what reports show
Cyclobenzaprine side effects
Cyclobenzaprine's FDA label: “Incidence of most common adverse reactions in the two double-blind*, placebo-controlled 5 mg studies (incidence of >3% on cyclobenzaprine hydrochloride 5 mg): Cyclobenzaprine Hydrochloride 5 mg N=464 Cyclobenzaprine Hydrochloride 10 mg N=249 Placebo N=469 …” FAERS holds 50,442 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is pain (5,150 reports).
- Generic listed
Check it at the source: the cyclobenzaprine FDA label on DailyMed (effective February 21, 2025, Jubilant Cadista Pharmaceuticals Inc.); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of cyclobenzaprine hydrochloride extended-release capsules?Cyclobenzaprine hydrochloride extended-release capsules may cause serious side effects, including: Serotonin syndrome is a serious medical condition that may happen when cyclobenzaprine hydrochloride extended-release capsules are taken with certain other medicines. Call your healthcare provider right away or go to the nearest hospital emergency room if you have some or all of these symptoms suggestive of serotonin syndrome: agitation, hallucinations, coma, or other changes in mental status coordination problems or muscle twitching (overactive reflexes) fast heartbeat, high or low blood pressure sweating or fever nausea, vomiting, or diarrhea muscle stiffness or tightness Cyclobenzaprine hydrochloride extended-release capsules may cause serious side effects that may lead to heart attack or stroke. […]
Source: FDA drug label (Cyclobenzaprine Hydrochloride), Teva Pharmaceuticals USA, Inc., effective May 31, 2024 (SPL set ca74d27a-f7c6-462d-a913-1cfa061bd8f3), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsIncidence of most common adverse reactions in the two double-blind*, placebo-controlled 5 mg studies (incidence of >3% on cyclobenzaprine hydrochloride 5 mg): Cyclobenzaprine Hydrochloride 5 mg N=464 Cyclobenzaprine Hydrochloride 10 mg N=249 Placebo N=469 Drowsiness 29% 38% 10% Dry Mouth 21% 32% 7% Fatigue 6% 6% 3% Headache 5% 5% 8% *Note: Cyclobenzaprine hydrochloride 10 mg data are from one clinical trial.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
| Reaction | Cyclobenzaprine Hydrochloride 5 mg N=464 | Cyclobenzaprine Hydrochloride 10 mg N=249 | Placebo N=469 |
|---|---|---|---|
| Drowsiness | 29% | 38% | 10% |
| Dry Mouth | 21% | 32% | 7% |
| Fatigue | 6% | 6% | 3% |
| Headache | 5% | 5% | 8% |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedIncidence of most common adverse reactions in the two double-blind*, placebo-controlled 5 mg studies (incidence of >3% on cyclobenzaprine hydrochloride 5 mg): Cyclobenzaprine Hydrochloride 5 mg N=464 Cyclobenzaprine Hydrochloride 10 mg N=249 Placebo N=469 Drowsiness 29% 38% 10% Dry Mouth 21% 32% 7% Fatigue 6% 6% 3% Headache 5% 5% 8% *Note: Cyclobenzaprine hydrochloride 10 mg data are from one clinical trial. Cyclobenzaprine hydrochloride 5 mg and placebo data are from two studies. Adverse reactions which were reported in 1% to 3% of the patients were: abdominal pain, acid regurgitation, constipation, diarrhea, dizziness, nausea, irritability, mental acuity decreased, nervousness, upper respiratory infection, and pharyngitis. The following list of adverse reactions is based on the experience in 473 patients treated with cyclobenzaprine hydrochloride 10 mg in additional controlled clinical studies, 7,607 patients in the postmarketing surveillance program, and reports received since the drug was marketed. The overall incidence of adverse reactions among patients in the surveillance program was less than the incidence in the controlled clinical studies. The adverse reactions reported most frequently with cyclobenzaprine were drowsiness, dry mouth and dizziness.
Source: FDA drug label, Jubilant Cadista Pharmaceuticals Inc., effective February 21, 2025 (SPL set 592871f6-0eb2-4624-9e10-bd8bf767c002), via openFDA; the full label on DailyMed
What do FAERS reports show?
50,442 reports list cyclobenzaprine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 7,185 are coded as a death and 14,099 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 22 reactions below, 11 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Cyclobenzaprine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions