Causality assessment · Expected pharmacological effect

Fluorouracil and Neutropenia: is the FAERS signal real?

n=5,175 co-reports · PRR 10.8 · ROR 11.5

Fluorouracil 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.

Expected pharmacological effect

Fluorouracil ↔ Neutropenia

n=5,175 co-reports · PRR 10.8 · ROR 11.5

Fluorouracil is an antimetabolite that causes myelosuppression with neutropenia, risk being higher in DPD deficiency; 5,175 co-reports give PRR 10.8. The label advises blood-count monitoring and awareness of dihydropyrimidine-dehydrogenase deficiency.

Regulatory basis: fluorouracil prescribing information — myelosuppression; blood-count monitoring and DPD caution.

Bradford Hill viewpoint	Status	Note
Temporality (necessary)	met	Days to weeks
Strength	met	PRR 10.8 with 5,175 co-reports
Consistency	met	Consistent across cohorts
Specificity	not established	Neutropenia has many causes
Biological gradient	met	Dose/metabolism-dependent
Plausibility	met	Known antimetabolite mechanism
Coherence	met	Fits fluorouracil myelosuppression
Experiment	n/a	Often coded in trials
Analogy	met	Analogous to capecitabine myelosuppression

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.

✓ Trial evidence found — Study of Nivolumab in Combination With Ipilimumab Compared to the Standard of Care (Extreme Regimen) as First Line Treatment in Patients With Recurrent or Metastatic Squamous Cell Carcinoma of the Head and Neck (NCT02741570)

Adverse event	Nivolumab + Ipilimumab (n=468) · EXTREME Regimen (n=441)
Neutropenia	0/468	2/441

Post-marketing signal terms appear in this trial's posted adverse-event tables; per-arm counts shown as affected/at-risk. View on ClinicalTrials.gov →