This medication is used to prevent disease caused by a virus called cytomegalovirus (CMV) in people who have received a bone marrow transplant or kidney transplant. CMV disease can cause serious infections, including an infection in the eye, called CMV retinitis, that can cause blindness. Letermovir is an anti-viral drug. It works by stopping the growth of the virus.

Read the Patient Information Leaflet if available from your pharmacist before you start using letermovir and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

This medication is given by injection into a vein, as directed by your doctor, usually once a day over 1 hour.

If you are using this medication at home, learn all preparation and usage instructions from your health care professional.

Before using, check this product for particles or discoloration. If either is present, do not use the liquid.

Learn how to store and discard needles and medical supplies safely.

The dosage is based on your medical condition, response to treatment, and other medications you may be taking. Children's dosage is also based on weight. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

For the best effect, use this medication at evenly spaced times. To help you remember, use this medication at the same time every day.

Continue to use this medication until the full prescribed amount is finished. Stopping the medication too early may result in an infection.

Nausea, diarrhea, vomiting, swelling ankles/feet, cough, or headache may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• fast/irregular heartbeat
• signs of kidney problems (such as change in the amount of urine)

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using letermovir, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• kidney disease
• liver disease

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

This medication can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include asunaprevir, elacestrant, elagolix, elbasvir/grazoprevir, ergot alkaloids (such as ergotamine, dihydroergotamine), flibanserin, lomitapide, pimozide, certain statin drugs (such as pitavastatin, simvastatin), tovorafenib, among others.

Other medications can affect the removal of letermovir from your body, which may affect how letermovir works. Examples include bosentan, certain HIV NNRTIs (such as efavirenz, etravirine, nevirapine), nafcillin, rifamycins (such as rifabutin, rifampin), St. John's wort, thioridazine, drugs used to treat seizures (such as carbamazepine, phenytoin), among others.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

This medication has been prescribed for your current condition only. Do not use it later to prevent another infection unless your doctor tells you to.

Lab and/or medical tests (such as kidney function) may be done while you are using this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, use it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Use your next dose at the regular time. Do not double the dose to catch up.

Consult the product instructions and your pharmacist for storage details. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.