Letermovir injection is used to help prevent cytomegalovirus (CMV) infection and disease in certain people who have received a hematopoietic stem-cell transplant (HSCT; a procedure that replaces diseased bone marrow with healthy bone marrow) and are at increased risk of developing a CMV infection. Letermovir is in a class of medications called antivirals. It works by slowing the growth of CMV.

Letermovir injection comes as a liquid to be diluted and given intravenously (into a vein). It is usually injected slowly over a period of 1 hour. It is usually given once a day for as long as you are unable to take letermovir tablets by mouth.

You may receive letermovir injection in a hospital, or you may administer the medication at home. If you will be receiving letermovir injection at home, your healthcare provider will show you how to use the medication. Be sure that you understand these directions, and ask your healthcare provider if you have any questions.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before using letermovir injection,

• Tell your doctor and pharmacist if you are allergic to letermovir, any other medications, or any of the ingredients in letermovir injection. Ask your pharmacist for a list of the ingredients.
• Tell your doctor if you are taking ergot alkaloids such as ergotamine (Ergomar, in Cafergot, Migergot) and dihydroergotamine (D.H.E. 45, Migranal), and pimozide (Orap). Your doctor will probably tell you not to take these medications if you are using letermovir injection.Also tell your doctor if you are taking cyclosporine along with either simvastatin or pitavastatin. Your doctor will probably tell you not to take these combinations of medications with letermovir.
• Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: amiodarone (Nexterone, Pacerone); cyclosporine (Gengraf, Neoral, Sandimmune); fentanyl (Actiq, Duragesic, Subsys, others); glyburide (Diabeta, Glynase); HMG-CoA reductase inhibitors such as atorvastatin (Lipitor, in Caduet), fluvastatin (Lescol), lovastatin (Altoprev), pitavastatin (Livalo, Zypitamag), pravastatin (Pravachol), rosuvastatin (Crestor), and simvastatin (Flolipid, Zocor, in Vytorin); omeprazole (Prilosec, in Yosprala, Zegerid); pantoprazole (Protonix); phenytoin (Dilantin, Phenytek); rifampin (Rifadin, Rimactane, in Rfater, Rifamate); sirolimus (Rapamune); quinidine (in Nuedexta); repaglinide (Prandin); rosiglitazone (Avandia); tacrolimus (Astagraf, Envarsus, Prograf); voriconazole (Vfend); and warfarin (Coumadin, Jantoven). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with letermovir injection, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
• Tell your doctor if you have or have ever had kidney or liver disease.
• Tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while using letermovir injection, call your doctor.
• If you are having surgery, including dental surgery, tell the doctor or dentist that you are using letermovir injection.

Unless your doctor tells you otherwise, continue your normal diet.

Letermovir injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Nausea
• Vomiting
• Diarrhea
• Abdominal pain
• Swelling of your arms or legs
• Headache
• Extreme tiredness

Some side effects can be serious. If you experience any of these symptoms call your doctor immediately:

• Fast or irregular heartbeat; feeling weak or dizzy, shortness of breath, chest pain

Letermovir injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your body’s response to letermovir.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.