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Generic name: letermovir (oral/injection) [ le-TERM-oh-vir ]
Drug class: Miscellaneous antivirals

Medically reviewed by Judith Stewart, BPharm. Last updated on Jun 20, 2023.

What is Prevymis?

Prevymis is a prescription antiviral medicine used to help prevent cytomegalovirus (CMV) infection and disease in people who have received a stem cell transplant or a kidney transplant and who have a high risk for getting CMV disease.

CMV is a common virus that rarely causes problems in healthy people, but can cause serious illness or even death in people with weakened immune systems, and especially those who have received an organ transplant or a stem cell transplant.

Prevymis is an antiviral medicine that works to prevent CMV infection and disease by inhibiting viral replication.

Prevymis is taken as an oral tablet once a day, or is given by your doctor as an injection through an IV line (intravenously) once a day if you are unable to take the tablets.

What is Prevymis used for?

Prevymis is used to prevent CMV infection and disease in adults who have received an allogeneic hematopoietic stem cell transplant and who are CMV seropositive.

An allogeneic hematopoietic stem cell transplant is a procedure in which a patient receives healthy blood-forming cells (stem cells) from a donor.  A CMV seropositive person has CMV virus in their blood but may not show any symptoms of infection. They are at risk of "reactivation" of the virus if the immune system becomes weakened.

Prevymis is also used to prevent CMV infection and disease in adults who have received a kidney transplant if they are CMV seronegative, but have received the kidney from from a CMV seropositive donor.


Tell your doctor about all your current medicines and any you start or stop using. Many drugs can interact with letermovir, and some drugs should not be used together.

Before taking this medicine

Some medicines can cause unwanted or dangerous effects when used with Prevymis. Your doctor may need to change your treatment plan if you use any of the following drugs:

To make sure Prevymis is safe for you, tell your doctor if you have ever had:

It is not known whether Prevymis will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It is not known whether letermovir passes into breast milk or if it could affect the nursing baby. Tell your doctor if you are breastfeeding.

How should I use Prevymis?

Use Prevymis exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not use this medicine in larger or smaller amounts or for longer than recommended.

Prevymis oral is a tablet taken by mouth. You may take the tablets with or without food.

Do not crush, chew, or break a Prevymis tablet. Swallow the tablet whole.

Prevymis injection is given as an infusion into a vein. A healthcare provider will give your first dose and may teach you how to properly use the medication by yourself.

Prepare an injection only when you are ready to give it. Do not use if the medicine looks cloudy, has changed colors, or has particles in it. Call your pharmacist for new medicine.

Do not give yourself this medicine if you do not understand how to use the injection and properly dispose of needles, IV tubing, and other items used.

You may need to mix the injection solution with a liquid (diluent) in an IV bag before using it. If you are using the injections at home, be sure you understand how to properly mix and store the medicine.

You can store the mixture for up to 24 hours at room temperature, or up to 48 hours in a refrigerator.

Prevymis injection must be given slowly, and the infusion can take at least 1 hour to use all of the medicine in the IV bag.

Prevymis tablets or injections are usually given once per day for up to 100 days if you have had a stem cell transplant and for up to 200 days if you have had a kidney transplant.

Use this medicine for the full prescribed length of time, even if you have no symptoms. Skipping doses may increase your risk of further infection that is resistant to medication.

Store tablets or unmixed injection solution in the original packaging at room temperature, away from moisture, heat, and light. Keep each tablet in the foil blister pack until you are ready to take a tablet.

Do not shake the injection solution bottle. Prepare your dose only when you are ready to give an injection.

Each single-use vial (bottle) of Prevymis injection is for one use only. Throw it away after one use, even if there is still medicine left inside.

Dosing information

Usual Adult Dose for CMV Prophylaxis:

480 mg orally or by IV infusion once a day

Co-administration with Cyclosporine: 240 mg orally or IV infusion once a day

Duration of therapy:
Allogeneic Hematopoietic Stem Cell Transplant (HSCT): through Day 100 post-transplantation
Kidney Transplant: through Day 200 post-transplantation

-Oral and IV doses may be used interchangeably; patients should be switched to oral therapy as soon as possible due to the presence of hydroxypropyl betadex in the IV formulation. IV infusions are administered over 1 hour. 
-During clinical trials, the median time to engraftment (defined as absolute neutrophil count of 500/mm3 or greater on 3 consecutive days after transplantation) was 19 days in letermovir-treated patients.
-Potentially significant drug interactions resulting in adverse reactions or reduced therapeutic effect of this drug or the concomitant drug are possible, therefore, consider drug interactions when initiating or completing therapy.

- Prophylaxis of cytomegalovirus (CMV) infection and disease in adult CMV-seropositive recipients [R+] of an allogeneic hematopoietic stem cell transplant (HSCT).
- Prophylaxis of CMV disease in adult kidney transplant recipients at high risk (Donor CMV seropositive/Recipient CMV seronegative [D+/R-]).

What happens if I miss a dose?

Use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while using Prevymis?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Prevymis side effects

Get emergency medical help if you have signs of an allergic reaction to Prevymis: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • fast or irregular heartbeats.

Serious side effects may occur if you also use certain other medications.

Common Prevymis side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Prevymis?

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Tell your doctor about all your current medicines and any you start or stop using. If you also use cyclosporine, your Prevymis dose will need to be adjusted.

Other drugs may interact with letermovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Frequently asked questions

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Prevymis only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.