Causality assessment · Causality: well established

Lenalidomide (IMiDs) and Venous thromboembolism: is the FAERS signal real?

n=7,546 co-reports · PRR 5.1 · ROR 5.1

Lenalidomide (IMiDs) 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

Lenalidomide (IMiDs) ↔ Venous thromboembolism

n=7,546 co-reports · PRR 5.1 · ROR 5.1

Lenalidomide, used in multiple myeloma and some blood cancers, raises the risk of venous thromboembolism — deep vein thrombosis and pulmonary embolism — especially when combined with steroids or in myeloma, which is why routine thromboprophylaxis (aspirin or an anticoagulant) is standard during therapy. The risk is a genuine, label-warned effect tied to the drug's immunomodulatory and procoagulant actions. The very high FAERS count (7,546 co-reports, PRR 5.1) reflects both the real effect and the drug's extensive use.

Regulatory basis: lenalidomide prescribing information (boxed warning for venous thromboembolism; thromboprophylaxis recommendations).

Bradford Hill viewpoint	Status	Note
Temporality (necessary)	met	Clots occur during therapy and the risk falls after withdrawal and with prophylaxis
Strength	met	PRR 5 on a very large co-report count
Consistency	met	Reproduced across myeloma trials
Specificity	met	A recognised IMiD effect, worse with steroids
Biological gradient	partial	Related to combination therapy and disease type
Plausibility	met	Procoagulant effects of the drug are the proposed mechanism
Coherence	met	Coheres with the boxed warning and routine thromboprophylaxis
Experiment	met	A randomized trial recorded pulmonary embolism on lenalidomide versus placebo
Analogy	met	Analogous to VTE risk with thalidomide and pomalidomide

This page's own qualitative read, not an automated/citation-gated assessment.

✓ Trial evidence found — A Study to Evaluate the Efficacy and Safety of Lenalidomide as Maintenance Therapy for Patients With B-Cell Chronic Lymphocytic Leukemia (CLL) Following Second Line Therapy (NCT00774345), N=315

Term (as recorded)	Lenalidomide (n=158)	Placebo (n=157)
Pulmonary embolism — Respiratory, thoracic and mediastinal disorders	4	1

Serious pulmonary embolism occurred in 4 of 158 patients on lenalidomide versus 1 of 157 on placebo in this maintenance trial — echoing the venous-thromboembolism signal that dictates routine thromboprophylaxis with lenalidomide. View on ClinicalTrials.gov →