Aspirin vs Warfarin: side effects in FDA adverse event reports
At a glance
| Aspirin | Warfarin | |
|---|---|---|
| Drug class | Nonsteroidal Anti-inflammatory Drug, Platelet Aggregation Inhibitor | – |
| Brand names | Cardiaspirin Protect | Warfarin Sodium |
| FAERS reports | 533,828 | 126,271 |
| Serious | 71% | 80% |
| Death outcome | 48,985 | 16,103 |
| Boxed warning | No | Yes BLEEDING RISK Warfarin sodium can cause major or fatal bleeding [see Warnings and Precautions (5.1) ] . Perform regular monitoring of INR in all treated patient |
Signals both drugs share
| Reaction | Aspirin | Warfarin | Label screen (A / B) |
|---|---|---|---|
| Retroperitoneal haemorrhage | 412 · PRR 7.7 | 261 · PRR 19.5 | Not in label — unassessed / Not in label — unassessed |
Labeled signals distinctive to Aspirin
- None stood out among the strongest labeled signals.
Labeled signals distinctive to Warfarin
- Calciphylaxis — n=729, PRR 110.2 Labeled — boxed warning
- Vascular calcification — n=134, PRR 23.6 Labeled (related wording)
- Catheter site pruritus — n=84, PRR 17.5 Labeled (related wording)
Common questions
Which has more reported side effects, Aspirin or Warfarin?
Aspirin has 533,828 FAERS reports and Warfarin 126,271. 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 (71% vs 80%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Aspirin and Warfarin share?
Both drugs carry disproportionality signals for retroperitoneal haemorrhage. Shared signals often reflect a shared drug class or the condition both are used for.
Is Aspirin or Warfarin 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.