Drug class · FAERS comparison

Nucleoside Metabolic Inhibitor side effects compared: 11 drugs, 284,852 FDA adverse event reports

Class as assigned in the FDA label (Established Pharmacologic Class) · data 2026-09-14

How to read this page. Report counts are not incidence rates: a drug with more reports is usually older, more widely used or more publicised, not more dangerous. Signals are screened against each product's FDA label on its own page; a term flagged across most of a class usually reflects the shared mechanism or the shared patient population.

Members

Drug	FAERS reports	Serious	Death outcome	Boxed warning	Top labeled signals	Unlabeled (unassessed)
Capecitabine	90,995	82%	18,292	boxed	Mucosal inflammation; Metastases to liver; Metastases to bone	Palmar-plantar erythrodysaesthesia syndrome; Metastases to lung
Fluorouracil	76,905	95%	10,861	boxed	Mucosal inflammation; Skin toxicity; Gastrointestinal toxicity	Dermatitis acneiform; Colorectal cancer metastatic
Cytarabine	59,730	97%	13,675	boxed	Secondary immunodeficiency; Abscess bacterial; Cytarabine syndrome	Febrile bone marrow aplasia; Neutropenic colitis
Azacitidine (Vidaza)	29,492	95%	10,775	–	Pneumonia fungal; Differentiation syndrome; Parainfluenza virus infection	Minimal residual disease; Allogenic stem cell transplantation
Azacitidine For (Azacitidine)	18,083	97%	5,996	–	Differentiation syndrome; Tissue infiltration	Myelosuppression; Pneumonia fungal
Decitabine	4,243	95%	1,154	–	Febrile neutropenia; Myelosuppression; Neutropenia	Bone marrow failure; Septic shock
Clofarabine	2,271	95%	900	–	Febrile neutropenia; Sepsis; Mucosal inflammation	Multiple organ dysfunction syndrome; Haematotoxicity
Pentostatin (Nipent)	1,048	92%	255	boxed	Neutropenia; Febrile neutropenia; Neutrophil count decreased	Lymphopenia; Thrombotic microangiopathy
Nelarabine	956	96%	210	boxed	Febrile neutropenia; Neurotoxicity; Neuropathy peripheral	Septic shock; Polyneuropathy
Cedazuridine and Decitabine (Inqovi)	875	82%	176	–	Cytopenia; Platelet count decreased; White blood cell count decreased	Transfusion
Gemcitabine Intravesical (Inlexzo)	254	23%	2	–	Dysuria; Micturition urgency; Haematuria	Pollakiuria

Class-wide signals (flagged in at least 6 of 11 members)

No term is flagged in at least half the members.

Member-specific signals (flagged in exactly one drug)

Reaction	Drug	Reports	PRR	Label screen
Lymphoid tissue hypoplasia	Cytarabine	144	16,580.1	Likely indication confounding
Thymus hypoplasia	Cytarabine	147	2,207.7	Not in label — unassessed
Human bocavirus infection	Cytarabine	132	814.2	Not in label — unassessed
Myelodysplastic syndrome transformation	Azacitidine	129	231.7	Likely indication confounding
Fingerprint loss	Capecitabine	74	194.8	Labeled (related wording)
Ductal adenocarcinoma of pancreas	Fluorouracil	108	176.5	Likely indication confounding
Cystitis bacterial	Cytarabine	110	168.1	Not in label — unassessed
Mantle cell lymphoma recurrent	Cytarabine	125	144.9	Likely indication confounding
Caecitis	Cytarabine	124	131.4	Not in label — unassessed
Dysuria	Gemcitabine Intravesical	54	117.4	Labeled adverse reaction
Diffuse large b-cell lymphoma refractory	Cytarabine	226	112.8	Likely indication confounding
Pik3ca-activated mutation	Capecitabine	107	112.7	Not in label — unassessed
Mycobacterium chelonae infection	Cytarabine	176	110.3	Not in label — unassessed
Dysaesthesia pharynx	Capecitabine	56	108.4	Not in label — unassessed
Disseminated aspergillosis	Cytarabine	106	102.6	Not in label — unassessed
Diffuse large b-cell lymphoma recurrent	Cytarabine	481	101.4	Likely indication confounding
Pollakiuria	Gemcitabine Intravesical	51	98.1	Not in label — unassessed
Secondary immunodeficiency	Cytarabine	256	95.8	Labeled — boxed warning
Abscess bacterial	Cytarabine	73	90.1	Labeled (related wording)
Colorectal cancer metastatic	Fluorouracil	561	88.6	Not in label — unassessed
Fusarium infection	Cytarabine	133	84.8	Not in label — unassessed
Malignant transformation	Cytarabine	86	83.2	Not in label — unassessed
Portal venous gas	Fluorouracil	81	81.3	Not in label — unassessed
Oesophageal fistula	Fluorouracil	70	76.9	Not in label — unassessed
Central hypothyroidism	Cytarabine	55	76.0	Not in label — unassessed

Common questions

Which nucleoside metabolic inhibitor has the most FDA adverse event reports?

Capecitabine has the most FAERS co-reports in this class (90,995), followed by Fluorouracil (76,905). Report volume tracks how widely and how long a drug has been used, and how much attention it has had, far more than its risk.

Which side effects are shared across nucleoside metabolic inhibitor drugs?

No reaction term is flagged in at least half of the members; the signals in this class are largely product-specific or population-specific.

Does a FAERS signal mean the drug causes the reaction?

No. These are disproportionality signals from voluntary reports with no denominator. Each is screened against the FDA label (known vs unlabeled) on the drug pages; causality needs temporality, dose-response, plausibility and trial or cohort evidence.

Sources: openFDA FAERS pair statistics (OpenPV build 2026-09-14), FDA labels via openFDA, seriousness and death counts from openFDA count queries. Generated 2026-10-08. Not medical advice.