What the label lists and what reports show
Fentanyl side effects
Fentanyl's FDA label: “As with other opioid agonists, the most common serious adverse reactions reported to occur with fentanyl are respiratory depression, apnea, rigidity and bradycardia; …” FAERS holds 114,879 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 drug abuse (12,447 reports).
- Generic listed
- In shortage
- Boxed warning
- DEA Schedule II
Check it at the source: the fentanyl FDA label on DailyMed (effective March 6, 2026, Hikma Pharmaceuticals USA Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsAs with other opioid agonists, the most common serious adverse reactions reported to occur with fentanyl are respiratory depression, apnea, rigidity and bradycardia; if these remain untreated, respiratory arrest, circulatory depression or cardiac arrest could occur.
Table 3. Adverse Reactions Reported by ≥1% of Fentanyl Transdermal System-treated…
This table is printed in the FENTANYL TRANSDERMAL label published by SpecGx LLC of April 30, 2026; the label quoted above does not print one.
| System/Organ ClassAdverse Reaction | Fentanyl Transdermal System%(N=216) | Placebo%(N=200) |
|---|---|---|
| Palpitations | 4 | 1 |
| Vertigo | 2 | 1 |
| Nausea | 41 | 17 |
| Vomiting | 26 | 3 |
| Constipation | 9 | 1 |
| Abdominal pain upper | 3 | 2 |
| Dry mouth | 2 | 0 |
| Fatigue | 6 | 3 |
| Feeling cold | 6 | 2 |
| Malaise | 4 | 1 |
| Asthenia | 2 | 0 |
| Edema peripheral | 1 | 1 |
| Anorexia | 5 | 0 |
| Muscle spasms | 4 | 2 |
| Somnolence | 19 | 3 |
| Dizziness | 10 | 4 |
| Insomnia | 10 | 7 |
| Depression | 1 | 0 |
| Hyperhidrosis | 6 | 1 |
| Pruritus | 3 | 2 |
| Rash | 2 | 1 |
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, continuedThe following serious adverse reactions are described, or described in greater detail, in other sections: Addiction, Abuse, and Misuse [see Warnings and Precautions (5.1 )] Life-Threatening Respiratory Depression [see Warnings and Precautions (5.2) ] Interactions with Benzodiazepines and Other CNS Depressants [see Warnings and Precautions (5.4) ] Severe Cardiovascular Depression [see Warnings and Precautions (5.6 )] Opioid-Induced Hyperalgesia and Allodynia [see Warnings and Precautions (5.7) ] Serotonin Syndrome [see Warnings and Precautions (5.8) ] Gastrointestinal Adverse Reactions [see Warnings and Precautions (5.11 )] Seizures [see Warnings and Precautions (5.12) ] The following adverse reactions associated with the use of fentanyl were identified in clinical studies or postmarketing reports. Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. As with other opioid agonists, the most common serious adverse reactions reported to occur with fentanyl are respiratory depression, apnea, rigidity and bradycardia; if these remain untreated, respiratory arrest, circulatory depression or cardiac arrest could occur. …
Source: FDA drug label, Hikma Pharmaceuticals USA Inc., effective March 6, 2026 (SPL set ce5db1c2-feb1-4ad2-847a-d02e865bd47e), via openFDA; the full label on DailyMed
What do FAERS reports show?
114,879 reports list fentanyl among the medicines taken, each a report of something that happened, not proof the medicine caused it; 33,716 are coded as a death and 36,144 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 19 reactions below, 8 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?
- Fentanyl: 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