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Letermovir Side Effects

The most commonly reported side effects of letermovir include off label use, cytomegalovirus infection reactivation, and death, based on 2,854 FDA adverse event reports from 2018 to 2025. 9.1% of reports found the drug to be ineffective.

Letermovir side effects

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

1
Off Label Use21.3%609
2
Drug Ineffective9.1%259
3
Cytomegalovirus Infection Reactivation7.0%199
4
Death6.2%178
5
Cytomegalovirus Infection5.9%169
6
Acute Kidney Injury5.7%163
7
Drug Interaction5.4%154
8
Product Use In Unapproved Indication5.0%144
9
Pancytopenia4.6%130
10
Drug Resistance3.1%88
11
Cytomegalovirus Viraemia3.0%86
12
Cystitis Haemorrhagic3.0%86
13
Hospitalisation2.9%84
14
Diarrhoea2.9%84
15
Bk Virus Infection2.9%84

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

Report severity

81.6%Serious2,330 reports
39.3%Hospitalizations1,123 reports
18.7%Fatal534 reports

Seriousness is determined by the reporter, not by OpenClaim.

Letermovir drug interactions

Other drugs that appear in adverse event reports alongside letermovir. 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
Tacrolimus12.6%361
2
Ganciclovir11.9%341
3
Mycophenolate10.5%300
4
Cyclosporine9.8%281
5
Cyclophosphamide9.3%266
6
Fludarabine-phosphate7.2%206
7
Prednisone7.1%203
8
Ruxolitinib6.7%190
9
Foscarnet-sodium6.1%174
10
Rituximab5.0%144
11
Acyclovir4.8%137
12
Methotrexate4.6%131
13
Methylprednisolone3.9%111
14
Posaconazole3.7%105
15
Sulfamethoxazole3.4%96

Taken alongside

1
Acyclovir26.8%764
2
Tacrolimus18.9%539
3
Prednisone13.1%374
4
Ursodiol12.0%342
5
Posaconazole10.8%307
6
Mycophenolate9.5%270
7
Ondansetron8.9%254
8
Pantoprazole-sodium8.8%252
9
Sulfamethoxazole8.5%243
10
Ganciclovir8.4%241
11
Trimethoprim7.9%226
12
Fluconazole7.6%216
13
Amlodipine7.0%201
14
Cyclosporine7.0%200
15
Acetaminophen7.0%199

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 letermovir side effects

36.5% of letermovir adverse event reports involve female patients and 48.6% involve male patients. The largest age group is adult at 72%. These figures reflect who reports side effects, not underlying risk.

Sex

Female36.5%
Male48.6%
Unknown14.9%

Age group

< 20.6%
2–114.9%
12–176.2%
18–6472.1%
65+16.1%

What is letermovir used for

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

Acute Graft Versus Host DiseaseAcute Lymphocytic LeukaemiaAcute Monocytic LeukaemiaAcute Myeloid LeukaemiaAllogenic Stem Cell TransplantationAntibiotic TherapyAntiviral ProphylaxisAntiviral TreatmentAplastic AnaemiaAbdominal PainAcute Graft Versus Host DiseaseAcute LeukaemiaAcute Leukaemia In RemissionAcute Lymphocytic LeukaemiaAcute Lymphocytic Leukaemia Recurrent

Showing 15 of 133 indications

Letermovir brand names and reporting trend

Letermovir is sold under the brand name Letermovir.

Brand names

Letermovir1,521

Quarterly reports (20182025)

20182020202220242025

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

Taking letermovir with another medication?

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