Causality assessment · Causality: well established

Allopurinol and Toxic epidermal necrolysis: is the FAERS signal real?

n=1,170 co-reports · PRR 11.3 · ROR 11.3

Allopurinol side-effect profile All assessments See in the full list

A written Bradford Hill assessment of one drug–event pair. The grade is a judgement about the signal, not a statement that this drug causes this event in any one person; FAERS counts are reports, not rates.

Causality: well established

Allopurinol ↔ Toxic epidermal necrolysis

n=1,170 co-reports · PRR 11.3 · ROR 11.3

Allopurinol can trigger toxic epidermal necrolysis and Stevens-Johnson syndrome, a severe cutaneous reaction closely associated with the HLA-B*5801 allele; 1,170 co-reports give PRR 11.3. The label recommends screening in high-prevalence ancestries and stopping the drug immediately if a rash develops.

Regulatory basis: allopurinol prescribing information — SJS/TEN and HLA-B*5801 screening.

Bradford Hill viewpoint	Status	Note
Temporality (necessary)	met	Days to weeks after start
Strength	met	PRR 11.3 with 1,170 co-reports
Consistency	met	Reproduced across cohorts
Specificity	met	Strong HLA association
Biological gradient	not established	Not clearly dose-related
Plausibility	met	Immune-mediated mechanism
Coherence	met	Fits aromatic-drug hypersensitivity
Experiment	n/a	Too rare for trial detection
Analogy	met	Analogous to carbamazepine SJS/TEN

This table is this page's own qualitative read of the literature cited above, not an automated or citation-gated assessment — see the note at the bottom of this page.

✗ No ClinicalTrials.gov results-posting trial in the top search hits for allopurinol captured toxic epidermal necrolysis as a tracked adverse event in a usable structure. Randomised gout trials were far too small to capture a rare HLA-linked eruption.