Applies to letermovir: oral tablet. Other dosage forms:

• intravenous solution

Serious side effects of Letermovir

Along with its needed effects, letermovir may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking letermovir:

More common

• Bloating or swelling of the face, arms, hands, lower legs, or feet
• rapid weight gain
• tingling of the hands or feet
• unusual weight gain or loss

Less common

• Dizziness
• fainting
• fast, pounding, or irregular heartbeat or pulse

Other side effects of Letermovir

Some side effects of letermovir may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• Cough
• diarrhea
• headache
• nausea
• stomach pain
• unusual tiredness or weakness
• vomiting

For Healthcare Professionals

Applies to letermovir: intravenous solution, oral tablet.

General

Side effects included those reported during treatment with study medication or within 2 weeks of study medication completion/discontinuation; the time for reporting side effects and laboratory abnormalities averaged about 22% longer with this drug compared to with placebo. The side effects most commonly reported included nausea, diarrhea, vomiting, peripheral edema, cough, headache, fatigue, and abdominal pain.^[Ref]

Hematologic

Decreased hemoglobin (less than 6.5 g/dL: 2%; 6.5 to less than 8 g/dL: 14%; 8 to less than 9.5 g/dL: 41%), platelets (less than 25,000 cells/mcL: 27%; 25,000 to less than 50,000 cells/mcL: 17%; 50,000 to less than 100,000 cells/mcL: 20%), and absolute neutrophil count (less than 500 cells/mcL: 19%; 500 to less than 750 cells/mcL: 4%; 750 to less than 1000 cells/mcL: 8%) were reported during therapy or within 2 weeks of stopping therapy.

Very common (10% or more): Decreased hemoglobin (up to 41%), decreased platelets (up to 27%), decreased absolute neutrophil count (up to 19%)

Gastrointestinal

Very common (10% or more): Nausea (27%), diarrhea (26%), vomiting (19%), abdominal pain (12%)

Renal

Very common (10% or more): Increased serum creatinine (up to 17%)

Increased serum creatinine (greater than 2.5 mg/dL: 2%; greater than 1.5 to 2.5 mg/dL: 17%) was reported during therapy or within 2 weeks of stopping therapy.

Other

Very common (10% or more): Peripheral edema (14%), fatigue (13%)

Nervous system

Very common (10% or more): Headache (14%)

Uncommon (0.1% to 1%): Dysgeusia, vertigo

Respiratory

Very common (10% or more): Cough (14%)

Frequency not reported: Dyspnea

Cardiovascular

The cardiac side effect rate was higher in patients using this drug (13%) compared to those using placebo (6%). Tachycardia (4% [compared to 2% with placebo]) and atrial fibrillation (3% [compared to 1% with placebo]) were the most commonly reported cardiac side effects. Most cardiac side effects were reported as mild or moderate in severity.

Common (1% to 10%): Tachycardia, atrial fibrillation

Hypersensitivity

Uncommon (0.1% to 1%): Hypersensitivity reaction

After switching from the oral formulation, hypersensitivity reaction (associated with moderate dyspnea) was reported in 1 patient after the first IV infusion; as a result, treatment was discontinued.

Hepatic

Uncommon (0.1% to 1%): Increased ALT, increased AST

Metabolic

Uncommon (0.1% to 1%): Decreased appetite

Musculoskeletal

Uncommon (0.1% to 1%): Muscle spasms