Warfarin and Warfarin-induced skin necrosis: is the FAERS signal real?
Warfarin ↔ Warfarin-induced skin necrosis
Warfarin can cause skin necrosis — a rare, painful, sometimes disfiguring reaction in which blood clots form in the small vessels of the skin, most often in the first days of therapy and in areas of fat such as the breast, thighs, and buttocks. It is thought to occur when warfarin's early depletion of protein C (a natural anticoagulant) briefly leaves the clotting system unbalanced, and it is why large loading doses are avoided and why protein-C-deficient patients are at particular risk. The 345 co-reports (PRR 11.7) reflect both the real effect and warfarin's enormous use.
Regulatory basis: warfarin prescribing information (skin necrosis warning; caution in protein C/S deficiency). Established warfarin-skin-necrosis literature.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | Necrosis appears in the first days of therapy and stops after withdrawal |
| Strength | partial | PRR 12 on a modest co-report count |
| Consistency | met | Reproduced across case series tied to protein C/S deficiency |
| Specificity | met | A distinctive warfarin effect |
| Biological gradient | partial | Linked to rapid initial dose and to protein-C deficiency |
| Plausibility | met | Early protein-C depletion unbalancing coagulation is the mechanism |
| Coherence | met | Coheres with the labelled caution and the avoidance of loading doses |
| Experiment | partial | Dechallenge (withdrawal, plus vitamin K in severe cases) resolves it; no randomized trial |
| Analogy | met | Analogous to skin necrosis reported with other vitamin-K antagonists |
This page's own qualitative read, not an automated/citation-gated assessment.