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Alemtuzumab Side Effects

The most commonly reported side effects of alemtuzumab include headache, fatigue, and off label use, based on 19,417 FDA adverse event reports from 2004 to 2025. 5.0% of reports found the drug to be ineffective.

Alemtuzumab side effects

Percentages show how often each reaction appears relative to total reports for alemtuzumab.

1
Headache9.5%1,851
2
Fatigue9.3%1,815
3
Off Label Use8.1%1,571
4
Pyrexia7.9%1,531
5
Rash5.9%1,152
6
Nausea5.7%1,113
7
Drug Ineffective5.0%974
8
Dyspnoea4.6%899
9
Multiple Sclerosis Relapse4.6%891
10
Asthenia4.5%882
11
Lymphocyte Count Decreased4.5%866
12
Urinary Tract Infection4.0%786
13
Pain3.8%734
14
Condition Aggravated3.6%698
15
Platelet Count Decreased3.3%645

These are voluntary reports and do not establish that alemtuzumab caused these reactions.

Report severity

86.3%Serious16,748 reports
31.9%Hospitalizations6,189 reports
15.6%Fatal3,032 reports

Seriousness is determined by the reporter, not by OpenClaim.

Alemtuzumab drug interactions

Other drugs that appear in adverse event reports alongside alemtuzumab. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Fludarabine-phosphate17.2%3,339
2
Cyclophosphamide10.0%1,945
3
Mycophenolate10.0%1,942
4
Tacrolimus9.4%1,820
5
Cyclosporine8.6%1,663
6
Methylprednisolone8.1%1,582
7
Busulfan7.3%1,408
8
Melphalan6.0%1,174
9
Prednisone6.0%1,157
10
Rituximab5.6%1,097
11
Methotrexate3.6%696
12
Vincristine-sulfate3.1%599
13
Doxorubicin-hydrochloride2.9%564
14
Thiotepa2.7%523
15
Dexamethasone2.4%467

Taken alongside

1
Acyclovir9.6%1,862
2
Acetaminophen9.5%1,836
3
Methylprednisolone9.3%1,801
4
Diphenhydramine5.6%1,097
5
Ranitidine4.9%943
6
Sulfamethoxazole4.8%929
7
Ergocalciferol4.7%905
8
Trimethoprim3.9%758
9
Cyclosporine3.7%726
10
Fludarabine-phosphate3.6%701
11
Mycophenolate3.6%691
12
Cetirizine-hydrochloride3.5%675
13
Tacrolimus3.2%622
14
Prednisone3.1%603
15
Fluconazole2.9%565

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports alemtuzumab side effects

47.1% of alemtuzumab adverse event reports involve female patients and 33.7% involve male patients. The largest age group is adult at 77%. These figures reflect who reports side effects, not underlying risk.

Sex

Female47.1%
Male33.7%
Unknown19.3%

Age group

< 23.9%
2–117.7%
12–173.1%
18–6477.0%
65+8.3%

What is alemtuzumab used for

Conditions and purposes for which patients were taking alemtuzumab when the adverse event was reported.

Abdominal Wall OperationAcquired HaemophiliaActivated Pi3 Kinase Delta SyndromeAcute Disseminated EncephalomyelitisAcute Graft Versus Host DiseaseAcute Graft Versus Host Disease In IntestineAcute Graft Versus Host Disease In LiverAcute Graft Versus Host Disease In SkinAcute LeukaemiaAcute Lymphocytic LeukaemiaAcute Lymphocytic Leukaemia RecurrentAcute Myeloid LeukaemiaAcute Myeloid Leukaemia RecurrentAcute Promyelocytic LeukaemiaAdenomatous Polyposis Coli

Showing 15 of 522 indications

Alemtuzumab brand names and reporting trend

Alemtuzumab is sold under the brand name Campath.

Brand names

Campath14,361

Quarterly reports (20042025)

20052010201520202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking alemtuzumab with another medication?

Ask OpenClaim about your specific drug combination. Get a sourced report using FDA data, drug labels, and medical literature.