Medically reviewed by Drugs.com. Last updated on Dec 21, 2021.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
- Tablet, Extended Release
Therapeutic Class: Antiretroviral Agent
Uses for fostemsavir
Fostemsavir is used together with other medicines to treat human immunodeficiency virus (HIV) infection in patients who have previously received other antiviral medicines, have HIV that is resistant to several antiviral medicines, or are using antiviral medicines that are not working or tolerated as well. HIV is the virus that causes acquired immune deficiency syndrome (AIDS).
Fostemsavir will not cure HIV infection or AIDS. It works by lowering the amount of HIV in the blood and helps the immune system. This may help delay some of the medical conditions that usually result from AIDS or HIV disease. It will not keep you from spreading HIV to other people.
Fostemsavir is available only with your doctor's prescription.
Before using fostemsavir
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For fostemsavir, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to fostemsavir or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of fostemsavir in the pediatric population. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of fostemsavir in the elderly. However, elderly patients are more likely to have age-related liver, kidney, heart, or heart rhythm problems, which may require caution in the dose for patients receiving fostemsavir.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking fostemsavir, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using fostemsavir with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- St John's Wort
Using fostemsavir with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Aripiprazole Lauroxil
- Arsenic Trioxide
- Ethinyl Estradiol
- Inotuzumab Ozogamicin
- Sodium Phosphate
- Sodium Phosphate, Dibasic
- Sodium Phosphate, Monobasic
Using fostemsavir with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of fostemsavir. Make sure you tell your doctor if you have any other medical problems, especially:
- Heart disease or
- Heart rhythm problems (eg, QT prolongation), history of or
- Liver disease (eg, hepatitis B or C infection), history of—Use with caution. May make these conditions worse.
Proper use of fostemsavir
Take fostemsavir exactly as directed by your doctor. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered.
Fostemsavir comes with a patient information leaflet. Read and follow these instructions carefully. Read it again each time you refill your prescription in case there is new information. Talk to your doctor if you have any questions.
Keep using fostemsavir for the full time of treatment, even if you or your child begin to feel better. It is also important that you continue taking all of the medicines that your doctor has given you for HIV infection.
Fostemsavir can be taken with or without food. Swallow the extended-release tablet whole. Do not crush, split, or chew it.
The extended-release tablets may have a slight vinegar-like odor. This is normal.
Do not change the dose or stop using fostemsavir without checking first with your doctor. When your supply of fostemsavir is running low, contact your doctor or pharmacist ahead of time. Do not allow yourself to run out of fostemsavir.
The dose of fostemsavir will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of fostemsavir. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (extended-release tablets):
- For treatment of HIV infection:
- Adults—600 milligrams (mg) 2 times a day.
- Children—Use and dose must be determined by your doctor.
- For treatment of HIV infection:
If you miss a dose of fostemsavir, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using fostemsavir
It is very important that your doctor check your progress at regular visits to make sure that fostemsavir is working properly. Blood tests may be needed to check for unwanted effects.
Do not use fostemsavir together with carbamazepine (Tegretol®), enzalutamide (Xtandi®), mitotane (Lysodren®), phenytoin (Dilantin®), rifampin (Rifadin®), or St. John’s wort.
Your immune system may get stronger when you start using HIV medicines. Tell your doctor right away if you or your child notice any changes in your health. Sometimes the immune system will start to fight infections that were hidden in your body, such as pneumonia, herpes, or tuberculosis. Autoimmune disorders (including Graves disease, polymyositis, and Guillain-Barré syndrome) may also occur.
Contact your doctor right away if you have any changes to your heart rhythm. You might feel dizzy or faint, or you might have a fast, pounding, or uneven heartbeat. Make sure your doctor knows if you had a heart rhythm problem, such as QT prolongation.
Fostemsavir does not treat hepatitis B or C virus infection. You should continue to take medicine for your hepatitis B or C infection during treatment with fostemsavir. Your hepatitis B infection may become active again if you stop your anti-hepatitis B treatment. Your doctor may also do blood tests to check your liver during treatment.
Fostemsavir does not decrease the risk of transmitting the HIV infection to others through sexual contact or by contaminated blood. Make sure you understand and practice safe sex, even if your partner also has HIV. Avoid sharing needles with anyone. If you have any questions about this, check with your doctor.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.
Fostemsavir side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- irregular heartbeat, recurrent
- itching, skin rash
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- tiredness or weakness
- burning, numbness, tingling, or painful sensations
- change in or loss of taste
- difficulty in moving
- joint pain or swelling
- muscle pain, cramps, or stiffness
- stomach discomfort, upset, or pain
- trouble sleeping
- unsteadiness or awkwardness
- weakness in the arms, hands, legs, or feet
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
More about fostemsavir
- Side effects
- Drug interactions
- Dosage information
- During pregnancy
- En español
- Drug class: miscellaneous antivirals
- Other brands
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