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Causality: well established
Causality assessment · Causality: well established
Phenobarbital and Stevens-Johnson syndrome: is the FAERS signal real?
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.
Phenobarbital ↔ Stevens-Johnson syndrome
n=88 co-reports · PRR 5.8 · ROR 5.8
Phenobarbital, an aromatic anticonvulsant, can cause severe cutaneous adverse reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis, linked to HLA alleles and cross-reactive with carbamazepine and phenytoin; 88 co-reports give PRR 5.8. The label warns of serious skin reactions, especially early in treatment and on re-exposure.
Regulatory basis: phenobarbital prescribing information — serious skin reactions/SJS; aromatic-anticonvulsant cross-reactivity caution.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | First weeks, or on re-exposure |
| Strength | met | PRR 5.8 with 88 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-anticonvulsant risk |
| Experiment | n/a | Too rare for trial detection |
| Analogy | met | Analogous to carbamazepine and phenytoin SJS |
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 phenobarbital captured stevens-johnson syndrome as a tracked adverse event in a usable structure. A rare, genotype-linked mucocutaneous eruption cannot be detected in randomised trials.