Generic name: fosamprenavir [ fos-am-PREN-a-vir ]
Drug class: Protease inhibitors
Medically reviewed by Drugs.com. Last updated on Mar 16, 2023.
Uses for fosamprenavir
Fosamprenavir is used in combination with other medicines to treat human immunodeficiency virus (HIV) infection. HIV is the virus that causes acquired immune deficiency syndrome (AIDS).
Fosamprenavir may slow down the destruction of the immune system caused by HIV. This may help delay problems that are usually related to AIDS or HIV disease from occurring. However, this medicine will not cure or prevent HIV infection, and it will not keep you from spreading the virus to other people. Patients who receive this medicine may continue to have other problems usually related to AIDS or HIV disease.
This medicine is available only with your doctor's prescription.
Before using fosamprenavir
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 this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine 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 performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of fosamprenavir in infants and children 4 weeks of age and older who have not taken HIV medicines in the past called protease inhibitors. Use is not recommended in children younger than 6 months of age who have taken HIV medicines called protease inhibitors in the past. Safety and efficacy have not been established in infants younger than 4 weeks of age.
Although appropriate studies on the relationship of age to the effects of fosamprenavir have not been performed in the geriatric population, geriatric-specific problems are not expected to limit the usefulness of fosamprenavir in the elderly. However, elderly patients are more likely to have age-related liver, kidney, or heart problems, which may require caution and an adjustment in the dose for patients receiving fosamprenavir.
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 this medicine, 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 this medicine 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.
- Ergoloid Mesylates
- St John's Wort
Using this medicine 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.
- Doxorubicin Hydrochloride Liposome
- Ethinyl Estradiol
- Sirolimus Protein-Bound
Using this medicine 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 this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
- Anemia, hemolytic or
- Cholesterol problem (high fat in the blood) or
- Diabetes or
- Hemophilia (a bleeding problem) or
- Hyperglycemia (high blood sugar) or
- Kidney problems (eg, kidney stones)—Use with caution. May make these conditions worse.
- Liver disease (including hepatitis B or C) or
- Sulfa allergy, history of—Use with caution. May cause side effects to become worse.
Proper use of fosamprenavir
Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. Also, do not stop taking this medicine without first checking with your doctor. When your supply of this medicine is running low, contact your doctor or pharmacist ahead of time. Do not allow yourself to run out of this medicine.
This medicine comes with a patient information leaflet. Read and follow the instructions carefully. Ask your doctor if you have any questions.
Fosamprenavir oral suspension should be taken by adults without food. Children should take the oral suspension with food.
Shake the oral suspension well before each use. Use a marked measuring spoon, oral syringe, or medicine cup to measure the dose. The average household teaspoon may not hold the right amount of liquid.
Fosamprenavir tablets may be taken with or without food. However, it should not be taken with a high-fat meal. Taking fosamprenavir with a high-fat meal may decrease the amount of fosamprenavir that is absorbed by the body and prevent the medicine from working properly.
It is important to take fosamprenavir as part of a combination treatment. Your dose of medicine will be based on what other medicines you are taking, as well as your weight. Be sure to take all the medicines your doctor has prescribed for you, including fosamprenavir.
Keep using fosamprenavir for the full time of treatment, even if you begin to feel better. If you stop the medicine even briefly, the virus may become harder to treat.
This medicine works best when there is a constant amount in the blood. To help keep the amount constant, do not miss any doses. Also, it is best to take the doses at evenly spaced times, day and night. For example, if you are to take two doses a day, the doses should be spaced about 12 hours apart. If you need help in planning the best times to take your medicine, check with your doctor.
Only take medicine that your doctor has prescribed especially for you. Do not share your medicine with others.
The dose of this medicine 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 this medicine. 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 forms (suspension or tablets):
- For treatment of HIV infection:
- Adults who have not taken HIV medicines called protease inhibitors in the past (fosamprenavir alone)—1400 milligrams (mg) (2 tablets) 2 times a day.
- Adults who have not taken HIV medicines called protease inhibitors in the past (fosamprenavir together with ritonavir)—1400 mg (2 tablets) fosamprenavir with 200 mg ritonavir once a day or 1400 mg (2 tablets) fosamprenavir with 100 mg ritonavir once a day or 700 mg fosamprenavir with 100 mg ritonavir 2 times a day.
- Adults who have taken HIV medicines called protease inhibitors in the past (fosamprenavir together with ritonavir)—700 mg fosamprenavir with 100 mg ritonavir 2 times a day. Adults who have taken protease inhibitors in the past should not take the combination of fosamprenavir with ritonavir only once a day. Check with your doctor if you are unsure of what amounts and how many times a day you should be taking your medicines. If you are taking fosamprenavir with ritonavir and efavirenz, check with your doctor for the correct doses.
- Children 4 weeks of age and older (fosamprenavir together with ritonavir)—Dose is based on body weight and must be determined by your doctor. The usual fosamprenavir suspension dose for patients weighing 20 kilograms (kg) or more is 18 milligrams (mg) per kilogram (kg) of body weight 2 times a day with ritonavir 3 mg per kg 2 times per day. Fosamprenavir doses up to 45 mg per kg 2 times per day with ritonavir 7 mg/kg 2 times a day are used for patients weighing less than 11 kg. However, the dose is usually not more than fosamprenavir 700 mg with ritonavir 100 mg 2 times a day.
- Children 2 years of age and older who have not taken HIV medicines called protease inhibitors in the past (fosamprenavir alone)—Dose is based on body weight and must be determined by your doctor. The usual suspension dose is 30 mg per kg of body weight 2 times a day. Doses up to 1400 mg (2 tablets) 2 times a day may be used for children weighing 47 kg or more.
- Children 4 weeks of age and older—Using fosamprenavir once a day is not recommended for children. Fosamprenavir should always be given twice daily unless otherwise determined by your doctor.
- Children younger than 4 weeks of age—Use and dose must be determined by your doctor.
- For treatment of HIV infection:
If you miss a dose of this medicine, 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.
If you or your child vomits 30 minutes after the first dose, a second dose should be taken right away.
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.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
The oral suspension may also be refrigerated. Do not freeze.
Precautions while using fosamprenavir
It is very important that your doctor check your or your child's progress at regular visits to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.
Do not use this medicine if you or your child are also using alfuzosin (Uroxatral®), cisapride (Propulsid®), delavirdine (Rescriptor®), flecainide (Tambocor®), lomitapide (Juxtapid®), lovastatin (Altocor®, Mevacor®), lurasidone (Latuda®), oral midazolam (Versed®), pimozide (Orap®), propafenone (Rythmol®), rifampin (Rifadin®, Rimactane®), sildenafil (Revatio®), simvastatin (Simcor®, Vytorin®, Zocor®), triazolam (Halcion®), or ergot medicines (eg, dihydroergotamine, ergonovine, ergotamine, methylergonovine, Cafergot®, D.H.E. 45®, Ergomar®, Ergostat®, Ergotrate®, Methergine®, Migranal®, or Wigraine®).
Serious skin reactions can occur with this medicine. Check with your doctor right away if you or your child have blistering, peeling, or loosening of the skin, itching, white spots in the mouth or on the lips, or redness of the skin.
Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be symptoms of a serious liver problem.
Your immune system may get stronger when you start taking HIV medicines. Tell your doctor right away if you notice any changes in your health. Sometimes the immune system will start to fight infections that were hidden in your body, such as pneumonia or tuberculosis, or may result in a flare-up of a hidden autoimmune disorder, such as Graves disease, polymyositis, or Guillain-Barré syndrome.
Tell your doctor if you are also using sildenafil (Viagra®), tadalafil (Cialis®), or vardenafil (Levitra®). Using these medicines together with fosamprenavir may increase your risk of having side effects such as low blood pressure, changes in vision, or prolonged erection of the penis.
Birth control pills may not work as well while you are using fosamprenavir. To keep from getting pregnant, use an additional form of birth control along with your pills. Other forms of birth control include condoms, a diaphragm, or contraceptive foam or jelly.
This medicine may increase blood sugar levels. Check with your doctor if you or your child notice a change in the results of your blood or urine sugar tests.
This medicine may cause bleeding problems, especially in patients with hemophilia (bleeding disorder). Check with your doctor right away if you or your child have back pain, blood in the eyes, blood in the urine, black, tarry stools, bruises or purple areas on the skin, decreased alertness, dizziness, headache, joint pain or swelling, nosebleeds, or coughing up blood.
This medicine may cause you to have excess body fat. Tell your doctor if you or your child notice changes in your body shape, such as an increased amount of fat in the upper back and neck, or around the chest and stomach area. You might also lose fat from the legs, arms, and face.
This medicine may increase your cholesterol and fats in the blood. If this condition occurs, your doctor may give you or your child some medicines that can lower the amount of cholesterol and fats in the blood.
This medicine may increase your risk of having kidney stones. Check with your doctor right away if you or your child have blood in your urine, nausea and vomiting, pain in the groin or genitals, or sharp back pain just below the ribs.
Tell your doctor that you or your child are using this medicine before you have any medical tests. The results of some tests may be affected by this medicine.
Fosamprenavir does not decrease the risk of transmitting the HIV infection to others through sexual contact or by contamination through blood. HIV may be acquired from or spread to others through infected body fluids, including blood, vaginal fluid, or semen. If you are infected, it is best to avoid any sexual activity involving an exchange of body fluids with other people. If you do have sex, always wear (or have your partner wear) a condom (“rubber”). Only use condoms made of latex, and use them every time you have vaginal, anal, or oral sex. The use of a spermicide (eg, nonoxynol-9) may also help prevent the spread of HIV if it is not irritating to the vagina, rectum, or mouth. Spermicides have been shown to kill HIV in lab tests. Do not use oil-based jelly, cold cream, baby oil, or shortening as a lubricant—these products can cause the condom to break. Lubricants without oil, such as K-Y Jelly, are recommended. Women may wish to carry their own condoms. Birth control pills and diaphragms will help protect against pregnancy, but they will not prevent someone from giving or getting the AIDS virus. If you inject drugs, get help to stop. Do not share needles or equipment 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 and nonprescription (over-the-counter [OTC]) medicines, and herbal (eg, St. John's wort) or vitamin supplements.
Side Effects of fosamprenavir
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:
- Black, tarry stools
- lower back or side pain
- painful or difficult urination
- pale skin
- skin rash
- sore throat
- ulcers, sores, or white spots in the mouth
- unusual bleeding or bruising
- unusual tiredness or weakness
Incidence not known
- Blistering, peeling, loosening of the skin
- blood in the urine
- chest pain or discomfort
- joint or muscle pain
- large amount of cholesterol in the blood
- large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or genitals
- pain in the groin or genitals
- pain or discomfort in the arms, jaw, back, or neck
- red skin lesions, often with a purple center
- red, irritated eyes
- sharp back pain just below the ribs
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:
- stomach pain
Incidence not known
- Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings in the mouth
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.
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