Letermovir

Letermovir 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 comes as a tablet to take by mouth. It is usually taken with or without food once a day. Your doctor will probably tell you to start taking letermovir after your receive the transplant and to stop taking the medication 100 days after the transplant. Take letermovir at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take letermovir exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Swallow the tablets whole; do not split, chew, or crush them.

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 taking letermovir,

• tell your doctor and pharmacist if you are allergic to letermovir, any other medications, or any of the ingredients in letermovir tablets. 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 taking letermovir. 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.
• some medications should not be taken with letermovir. Other medications may cause dosing changes or extra monitoring when taken with letermovir injection. Make sure you have discussed any medications you are currently taking or plan to take before starting letermovir with your doctor and pharmacist. Before starting, stopping, or changing any medications while taking letermovir, please get the advice of your doctor or pharmacist.
• the following nonprescription or herbal products may interact with letermovir: St. John's wort; omeprazole (Prilosec). Be sure to let your doctor and pharmacist know that you are taking these medications before you start letermovir. Do not start any of these medications while taking letermovir without discussing with your healthcare provider.
• 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 taking letermovir, call your doctor.
• if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking letermovir.

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

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Letermovir 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 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 (https://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. https://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (https://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

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.

• Prevymis^®