Dapsone and Methaemoglobinaemia / haemolysis: is the FAERS signal real?
Dapsone ↔ Methaemoglobinaemia / haemolysis
Dapsone, used for leprosy, dermatitis herpetiformis, and some opportunistic infections, oxidises haemoglobin to methaemoglobin and can also cause haemolytic anaemia, particularly in people with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Methaemoglobinaemia produces cyanosis and breathlessness with a normal oxygen level on the monitor — a signature that is easy to misread — and reverses with methylene blue. The 480 co-reports (PRR 522.3) reflect both the real effect and the drug's narrower, mostly dermatology and infectious-disease use.
Regulatory basis: dapsone prescribing information (methaemoglobinaemia and haemolysis warnings; G6PD screening). Established dapsone-oxidative-haemolysis literature.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | Methaemoglobinaemia develops during therapy and reverses with methylene blue and withdrawal |
| Strength | met | Very high PRR, on a modest co-report count |
| Consistency | met | Reproduced across the dapsone literature |
| Specificity | met | A distinctive oxidative consequence of dapsone, unlike most drugs |
| Biological gradient | partial | Dose-related and much worse in G6PD deficiency |
| Plausibility | met | Direct oxidation of haemoglobin iron and oxidative red-cell injury are the mechanisms |
| Coherence | met | Coheres with the labelled warnings and G6PD screening |
| Experiment | partial | Dechallenge (withdrawal) plus methylene blue reverses it; no randomized trial |
| Analogy | met | Analogous to methaemoglobinaemia from other oxidising drugs (nitrites, prilocaine, some antimalarials) |
This page's own qualitative read, not an automated/citation-gated assessment.