Morphine vs Fentanyl: side effects in FDA adverse event reports
At a glance
| Morphine | Fentanyl | |
|---|---|---|
| Drug class | Opioid Agonist | Opioid Agonist |
| Brand names | Opium | Fentanyl System |
| FAERS reports | 120,577 | 97,898 |
| Serious | 86% | 85% |
| Death outcome | 34,831 | 27,747 |
| Boxed warning | No | Yes SERIOUS AND LIFE-THREATENING RISKS FROM USE OF FENTANYL TRANSDERMAL SYSTEM . WARNING: SERIOUS AND LIFE-THREATENING RISKS FROM USE OF FENTANYL TRANSDERMAL SYSTEM |
Signals both drugs share
| Reaction | Morphine | Fentanyl | Label screen (A / B) |
|---|---|---|---|
| Radiculopathy | 189 · PRR 13.4 | 179 · PRR 15.5 | No label text to screen / Not in label — unassessed |
| Female genital tract fistula | 167 · PRR 18.6 | 153 · PRR 20.8 | No label text to screen / Not in label — unassessed |
| Vaginal flatulence | 142 · PRR 151.4 | 125 · PRR 148.5 | No label text to screen / Not in label — unassessed |
Labeled signals distinctive to Morphine
- None stood out among the strongest labeled signals.
Labeled signals distinctive to Fentanyl
- Serotonin syndrome — n=1,318, PRR 15.8 Labeled adverse reaction
- Respiratory depression — n=920, PRR 17.3 Labeled — boxed warning
- Prescription drug used without a prescription — n=629, PRR 24.5 Labeled (related wording)
- Hyperthermia malignant — n=225, PRR 38.4 Labeled (related wording)
- Accidental death — n=148, PRR 18.5 Labeled (related wording)
- Intensive care unit acquired weakness — n=60, PRR 39.8 Labeled (related wording)
Common questions
Which has more reported side effects, Morphine or Fentanyl?
Morphine has 120,577 FAERS reports and Fentanyl 97,898. More reports does not mean more dangerous: volume follows how widely and how long a drug has been used, prescription vs over-the-counter status, and publicity. The seriousness share (86% vs 85%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Morphine and Fentanyl share?
Both drugs carry disproportionality signals for radiculopathy, female genital tract fistula, vaginal flatulence. Shared signals often reflect a shared drug class or the condition both are used for.
Is Morphine or Fentanyl safer?
FAERS cannot answer that: it has no denominator and no comparator. Use this page to see which risks are already on each label and which signals are unlabeled, then check the prescribing information and your clinician for your situation.
Sources: openFDA FAERS pair statistics (OpenPV build 2026-09-14), FDA labels via openFDA, openFDA count queries for seriousness and deaths. Pair chosen because it is a commonly searched comparison. Generated 2026-10-08.