What the label lists and what reports show

Imatinib side effects

Imatinib's FDA label: “The most frequently reported adverse reactions (greater than or equal to 30%) were edema, nausea, vomiting, muscle cramps, musculoskeletal pain, diarrhea, rash, fatigue and abdominal pain.” FAERS holds 41,417 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is nausea (2,848 reports).

Generic listed

Check it at the source: the imatinib FDA label on DailyMed (effective September 8, 2026, Apotex Corp); the FDA FAERS public dashboard.

What does the label list?

From the label: adverse reactions
The most frequently reported adverse reactions (greater than or equal to 30%) were edema, nausea, vomiting, muscle cramps, musculoskeletal pain, diarrhea, rash, fatigue and abdominal pain.

A table the label prints in its adverse reactions section without a title; its column headings name the groups compared

Preferred term	Imatinib mesylate N = 551 (%)	IFN+Ara−C N = 533 (%)	Imatinib mesylate N = 551 (%)	IFN+Ara−C N = 533 (%)
Fluid retention	61.7	11.1	2.5	0.9
− Superficial edema	59.9	9.6	1.5	0.4
− Other fluid retention reactions 2	6.9	1.9	1.3	0.6
Nausea	49.5	61.5	1.3	5.1
Muscle cramps	49.2	11.8	2.2	0.2
Musculoskeletal pain	47	44.8	5.4	8.6
Diarrhea	45.4	43.3	3.3	3.2
Rash and related terms	40.1	26.1	2.9	2.4
Fatigue	38.8	67	1.8	25.1
Headache	37	43.3	0.5	3.8
Joint pain	31.4	38.1	2.5	7.7
Abdominal pain	36.5	25.9	4.2	3.9
Nasopharyngitis	30.5	8.8	0	0.4
Hemorrhage	28.9	21.2	1.8	1.7
- GI hemorrhage	1.6	1.1	0.5	0.2
- CNS hemorrhage	0.2	0.4	0	0.4
Myalgia	24.1	38.8	1.5	8.3
Vomiting	22.5	27.8	2	3.4
Dyspepsia	18.9	8.3	0	0.8
Cough	20	23.1	0.2	0.6
Pharyngolaryngeal pain	18.1	11.4	0.2	0
Upper respiratory tract infection	21.2	8.4	0.2	0.4
Dizziness	19.4	24.4	0.9	3.8
Pyrexia	17.8	42.6	0.9	3
Weight increased	15.6	2.6	2	0.4

Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.

From the label: adverse reactions, continued
The following serious adverse reactions are described elsewhere in the labeling: Fluid Retention and Edema [see Warnings and Precautions ( 5.1 )] Hematologic Toxicity [see Warnings and Precautions ( 5.2 )] Congestive Heart Failure and Left Ventricular Dysfunction [see Warnings and Precautions ( 5.3 )] Hepatotoxicity [see Warnings and Precautions ( 5.4 )] Hemorrhage [see Warnings and Precautions ( 5.5 )] Gastrointestinal Disorders [see Warnings and Precautions ( 5.6 )] Hypereosinophilic Cardiac Toxicity [see Warnings and Precautions ( 5.7 )] Dermatologic Toxicities [see Warnings and Precautions ( 5.8 )] Hypothyroidism [see Warnings and Precautions ( 5.9 )] Growth Retardation in Children and Adolescents [see Warnings and Precautions ( 5.11 )] Tumor Lysis Syndrome [see Warnings and Precautions ( 5.12 )] Impairments Related to Driving and Using Machinery [see Warnings and Precautions ( 5.13 )] Renal Toxicity [see Warnings and Precautions ( 5.1 4 ) ] The most frequently reported adverse reactions (greater than or equal to 30%) were edema, nausea, vomiting, muscle cramps, musculoskeletal pain, diarrhea, rash, fatigue and abdominal pain. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Apotex Corp. at 1-800-706-5575 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. …

Source: FDA drug label, Apotex Corp, effective September 8, 2026 (SPL set 0291eca5-7a1d-4a79-30be-252224d96509), via openFDA; the full label on DailyMed

What do FAERS reports show?

41,417 reports list imatinib among the medicines taken, each a report of something that happened, not proof the medicine caused it; 8,912 are coded as a death and 9,005 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 21 reactions below, 14 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.

Reports received each year

The 25 most reported reactions

Death (an outcome recorded in the report)5,158
Nausea (named in the label)2,848
Drug Ineffective (a use or a product term, not a reaction)2,817
Diarrhoea (named in the label)2,511
Fatigue (named in the label)2,118
Vomiting (named in the label)1,795
Dyspnoea (named in the label)1,475
Malignant Neoplasm Progression1,427
Rash (named in the label)1,394
Malaise1,378
Drug Intolerance1,221
Drug Resistance1,219
Asthenia (named in the label)1,181
Pyrexia (named in the label)1,170
Anaemia (named in the label)1,136
Muscle Spasms (named in the label)1,128
Headache (named in the label)1,030
Pleural Effusion (named in the label)1,025
Arthralgia (named in the label)1,000
Abdominal Pain (named in the label)953
Disease Progression (a use or a product term, not a reaction)914
Off Label Use (a use or a product term, not a reaction)898
Neoplasm Malignant868
Chronic Myeloid Leukaemia860
Pain853

Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms

What next?

Imatinib: the full record: label, generics, price, shortages, recalls
Report a side effect to the FDA: MedWatch
Side effects hub: the most reported medicines and reactions