PREVYMIS® 240 mg film-coated tablets – patient leaflet, side effects, dosage

1. What PREVYMIS is and what it is used for

PREVYMIS is an antiviral prescription medicine that contains the active substance letermovir.

PREVYMIS is a medicine for:

• adults and children weighing at least 15 kg who have

  recently had a stem cell (bone marrow) transplant.

• adults and children weighing at least 40 kg who have

  recently had a kidney transplant.

The medicine helps stop you from getting ill from CMV (‘cytomegalovirus’).

CMV is a virus. For most people, CMV does not hurt them. However, if your immune system is weak after you get a stem cell transplant or a kidney transplant, you may be at high risk of becoming ill from CMV.

2. What you need to know before you take PREVYMIS

Do not take PREVYMIS if:

• you are allergic to letermovir or any of the other ingredients

  of this medicine (listed in section 6).

• you take either of these medicines:

  • pimozide - used for Tourette’s syndrome

  • ergot alkaloids (such as ergotamine and

    dihydroergotamine) - used for migraine headaches.

• you take the following herbal product:

  • St. John’s wort (Hypericum perforatum)

Do not take PREVYMIS if any of the above apply to you. If you are not sure, talk to your doctor, pharmacist or nurse before taking PREVYMIS.

If you are taking PREVYMIS with ciclosporin, do not take the following medicines:

• dabigatran - used for blood clots

• atorvastatin, simvastatin, rosuvastatin, pitavastatin - for

  high cholesterol.

Warnings and precautions

If you are also taking a medicine for high cholesterol (see list of medicines in section “Other medicines and PREVYMIS” below) you must tell your doctor immediately if you have unexplained muscle aches or pains especially if you feel unwell or have a fever. Your medicine or dose may then need to be changed. See the package leaflet for your other medicine for further information.

Additional blood tests may be needed to monitor the following medicines:

• ciclosporin, tacrolimus, sirolimus
• voriconazole

Children and adolescents

PREVYMIS is not for use in children weighing less than 5 kg who have had a stem cell (bone marrow) transplant or in children weighing less than 40 kg who have had a kidney transplant. This is because PREVYMIS has not been tested in these groups.

Other medicines and PREVYMIS

Tell your doctor or pharmacist if you are taking, have recently taken, or might take any other medicines. This is because PREVYMIS may affect the way other medicines work, and other medicines may affect how PREVYMIS works. Your doctor or pharmacist will tell you if it is safe to take PREVYMIS with other medicines.

There are some medicines you must not take with PREVYMIS (see list under “Do not take PREVYMIS if:”).

There are some additional medicines you must not take with PREVYMIS and ciclosporin (see list under “If you are taking PREVYMIS with ciclosporin, do not take the following medicines:”).

Also tell your doctor if you are taking any of the following medicines. This is because your doctor may have to change your medicines or change the dose of your medicines:

• alfentanil - for severe pain
• fentanyl - for severe pain
• quinidine - for abnormal heart rhythms

• ciclosporin, tacrolimus, sirolimus - used to prevent transplant

  rejection

• voriconazole - for fungal infections

• statins, such as atorvastatin, fluvastatin, rosuvastatin,

  simvastatin, pravastatin, pitavastatin - for high cholesterol

• glyburide, repaglinide - for high blood sugar

• carbamazepine, phenobarbital, phenytoin - for fits or

  seizures

• dabigatran, warfarin - used to thin the blood or for

  blood clots

• midazolam - used as a sedative
• amiodarone - used to correct irregular heartbeats
• oral contraceptive steroids - for birth control

• omeprazole, pantoprazole - for stomach ulcers and other

  stomach problems

• nafcillin - for bacterial infections
• rifabutin, rifampicin - for mycobacterial infections
• thioridazine - for psychiatric disorders
• bosentan - for high blood pressure in the vessels in the lungs
• efavirenz, etravirine, nevirapine, lopinavir, ritonavir - for HIV
• modafinil - for wakefulness

You can ask your doctor or pharmacist for a list of medicines that may interact with PREVYMIS.

Pregnancy

If you are pregnant, think you may be pregnant, or are planning to have a baby, ask your doctor for advice before taking this medicine. PREVYMIS is not recommended in pregnancy. This is because it has not been studied in pregnancy and it is not known if PREVYMIS will harm your baby while you are pregnant.

Breast-feeding

If you are breast-feeding or are planning to breast-feed, tell your doctor before taking this medicine. Breast-feeding is not recommended while taking PREVYMIS. This is because it is not known if PREVYMIS gets in your breast milk and will be passed to your baby.

Driving and using machines

PREVYMIS may have minor influence on your ability to drive and use machines (see section 4 “Possible side effects” below).

Some patients have reported fatigue (feeling very tired) or vertigo (feeling like you are spinning) during treatment with PREVYMIS. If you experience any of these effects, do not drive or use machines until the effect wears off.

PREVYMIS contains lactose

PREVYMIS contains lactose monohydrate. If you have been told by your doctor that you have an intolerance to some sugars, contact your doctor before taking this medicinal product.

PREVYMIS contains sodium

This medicine contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially ‘sodium-free’.

3. How to take PREVYMIS

Always take this medicine exactly as your doctor or pharmacist has told you. Check with your doctor or pharmacist if you are not sure.

How much to take

Your dose of PREVYMIS depends on how much you weigh and if you are also taking ciclosporin. Your doctor will tell you how many tablets to take.

• Take PREVYMIS as directed once a day.
• Take PREVYMIS at the same time every day.

• Take it with or without food.

The recommended oral doses of PREVYMIS are provided in Table 1 and Table 2.

Table 1: The recommended doses of PREVYMIS film-coated tablets without ciclosporin

Table 2: The recommended doses of PREVYMIS film-coated tablets with ciclosporin

How to take

• Swallow the tablet whole with some water. Do not break, crush, or chew the tablet because these methods have not been studied.

If you take more PREVYMIS than you should

If you take more PREVYMIS than you should, call your doctor straight away.

If you forget to take PREVYMIS

It is very important that you do not miss or skip doses of PREVYMIS.

• If you forget a dose, take it as soon as you remember.

  However, if it is nearly time for the next dose, skip the missed dose. Take your next dose at the usual time.

• Do not take two doses of PREVYMIS at the same time to make up for a missed dose.
• If you are not sure what to do, call your doctor or pharmacist.

Do not stop taking PREVYMIS

Do not stop taking PREVYMIS without talking to your doctor first. Do not run out of PREVYMIS. This will give the medicine the best chance to keep you from becoming ill from CMV after you get a stem cell transplant or a kidney transplant.

If you have any further questions on the use of this medicine, ask your doctor, pharmacist, or nurse.

4. Possible side effects

Like all medicines, this medicine can cause side effects, although not everybody gets them.

Common: may affect up to 1 in 10 people

• diarrhoea
• feeling sick (nausea)
• being sick (vomiting)

Uncommon: may affect up to 1 in 100 people

• allergic reaction (hypersensitivity) – the signs may include wheezing, difficulty breathing, rashes or hives, itchiness, swelling
• loss of appetite
• changes in taste
• headache
• feeling like you are spinning (vertigo)

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• stomach ache

• abnormalities in laboratory tests of liver function

  (i.e., raised levels of liver enzymes)

• muscle spasms
• high blood creatinine - shown in blood tests
• feeling very tired (fatigue)
• swelling of hands or feet

Reporting of side effects

If you get any side effects, talk to your doctor, pharmacist, or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.

5. How to store PREVYMIS

Keep this medicine out of the sight and reach of children.

Do not use this medicine after the expiry date which is stated on the carton and blister card after EXP. The expiry date refers to the last day of that month.

This medicine does not require any special temperature storage conditions. Store in the original package in order to protect from moisture.

Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help to protect the environment.

6. Contents of the pack and other information

What PREVYMIS contains

The active substance is letermovir. Each film-coated tablet contains 240 mg letermovir.

The other ingredients are:

Tablet core

Microcrystalline cellulose (E460), croscarmellose sodium (E468), povidone (E1201), colloidal anhydrous silica (E551), magnesium stearate (E470b).

Film-coating

Lactose monohydrate, hypromellose (E464), titanium dioxide (E171), triacetin, iron oxide yellow (E172), carnauba wax (E903). See section 2 “PREVYMIS contains lactose” and “PREVYMIS contains sodium”.

What PREVYMIS looks like and contents of the pack

PREVYMIS 240 mg film-coated tablet (“tablet”) is a yellow oval tablet, debossed with “591” on one side and corporate logo on the other side. The tablet is 16.5 mm long and 8.5 mm wide.

The 28x1 tablets are packaged into a carton containing Polyamide/Aluminium/PVC – Aluminium perforated unit dose blister cards (total of 28 tablets).

Marketing Authorisation Holder and Manufacturer Marketing Authorisation Holder: Merck Sharp & Dohme (UK) Limited, 120 Moorgate, London, EC2M 6UR, UK.

Manufacturer: Merck Sharp & Dohme B.V., Waarderweg 39, 2031 BN Haarlem, The Netherlands.

For any information about this medicine, please contact: Merck Sharp & Dohme (UK) Limited

Tel: +44 (0) 208 154 8000

Email: medicalinformationuk@msd.com

This leaflet was last revised in July 2025

© 2025 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.

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