How does this medication work? What will it do for me?

Fosamprenavir belongs to the group of medications known as protease inhibitors. It is used in combination with other medications to treat adults and children at least 6 years old that have human immunodeficiency virus (HIV) infection.

Fosamprenavir does not cure HIV or AIDS and does not prevent it from being spread to others. It does slow further growth or reproduction of HIV when used in combination with other medications, and it seems to slow down the destruction of the immune system. This may help to delay the development of problems that are related to AIDS or HIV disease.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each pink, capsule-shaped tablet with the letters "GX LL&" printed on one side, contains 700 mg of fosamprenavir calcium. Nonmedicinal ingredients: colloidal silicon dioxide, croscarmellose sodium, magnesium stearate, microcrystalline cellulose, povidone K30, hypromellose, iron oxide red, titanium dioxide, and triacetin.

Oral Suspension
Each mL of white to off-white colour oral suspension with grape bubblegum and peppermint flavouring contains 50 mg of fosamprenavir calcium. Nonmedicinal ingredients: hypromellose, sucralose, propylene glycol, methyl parahydroxybenzoate, propyl parahydroxybenzoate, polysorbate 80, calcium chloride dihydrate, artificial grape bubblegum flavour, natural peppermint flavour, and purified water.

How should I use this medication?

For people who have not taken a protease inhibitor before, the usual recommended dose of fosamprenavir for adults 18 years of age and older is 1,400 mg (along with 200 mg of ritonavir) daily or 700 mg (along with 100 mg of ritonavir) twice daily. People who have taken a protease inhibitor in the past should follow the twice-daily regimen. The capsules should be swallowed whole with or without food. They should not be crushed or chewed. When adults take the oral suspension, they should shake the bottle vigorously and take the prescribed dose on an empty stomach.

For children older than 6 years of age, the dose of this medication is determined by your doctor based on body weight (but it should not exceed the recommended adult dose) and is taken twice daily. Children should take the suspension with food. If vomiting occurs within 30 minutes of receiving a dose, the dose should be taken again. The suspension should be shaken vigorously before use.

Use an oral syringe to measure each dose of the suspension, as it gives a more accurate measurement than household teaspoons.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Both the tablet and suspension forms of fosamprenavir may be stored at room temperature. Keep this and all medication out of the reach of children. Do not allow the suspension to freeze. Discard the suspension 28 days after first opening.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to fosamprenavir, amprenavir, ritonavir, or any ingredients of the medication
  • are taking any of the following:
    • alpha blockers (e.g., alfuzosin, doxazosin, tamsulosin)
    • astemizole
    • benzodiazepines (e.g., diazepam, flurazepam, midazolam, triazolam)
    • cisapride
    • delavirdine
    • ergot derivatives (e.g., dihydroergotamine, ergonovine, ergotamine, methylergonovine)
    • lurasidone
    • medications for irregular heartbeat such as amiodarone, disopyramide, dofetilide, flecainide, procainamide, propafenone, quinidine, or sotalol
    • sildenafil (for the treatment of pulmonary arterial hypertension)
    • pimozide
    • quetiapine
    • rifampin
    • St. John's wort
    • "statin" anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
    • terfenadine

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • abdominal pain
  • diarrhea
  • fatigue
  • gas
  • headache
  • nausea
  • skin rash (mild)
  • tingling or numbness around the mouth
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • fast or pounding heartbeat
  • increased body fat in the back and neck (buffalo hump), breasts, and torso; and a loss of fat from the legs, arms, and face
  • joint or muscle pain
  • signs of infection (e.g., fever, chills, severe diarrhea, shortness of breath, unusual tiredness or weakness)
  • signs of liver problems (e.g., darkening of urine, pale stools, yellow eyes or skin)
  • symptoms of high blood sugar (e.g., increased hunger, increased thirst, increased urination)
  • symptoms of kidney stones (e.g., pain in the lower back to the groin, nausea, vomiting, blood in the urine, decreased urination)
  • unexplained bleeding or bruising (for people with haemophilia)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • severe skin reaction (e.g., blistering, peeling, or loosening of the skin and mucous membranes)
  • signs of a serious allergic reaction (e.g., swelling of face, throat, or tongue; hives; or difficulty breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Birth control: Your doctor may advise that you stop using hormonal birth control pills while taking fosamprenavir. Birth control pills may be less effective while you are taking this medication. Taking birth control pills while taking this medication also can increase the risk of developing liver problems. An alternate nonhormonal birth control method (e.g., condoms) should be used to prevent pregnancy.

Bleeding risk: People with hemophilia may be more likely to bleed while taking this medication.

Cholesterol and triglycerides: This medication may cause increases in cholesterol and triglyceride levels. Your doctor will check these levels before and during treatment.

Fat redistribution: Over time, this medication may change how fat is distributed in your body and may change your body shape. You may notice increased fat in the upper back, neck, and breasts, as well as around the back, chest, and stomach area. You may also notice loss of fat from the legs, arms, and face. The long-term effects of this are not known.

Diabetes: This medication may increase blood glucose (sugar) levels in the body. It may also increase the risk of developing diabetes. If you have diabetes or have risk factors for developing diabetes, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Although your doctor will check your blood glucose levels through blood tests while you are taking this medication, report any symptoms of high blood sugar (e.g., increased hunger, increased thirst, increased urination) to your doctor.

Drug interactions: There are life-threatening interactions that can occur between fosamprenavir and many other medications. For your safety, if you are thinking about or using any other medication, prescription or non-prescription, you should check with your doctor or pharmacist first. See the "What other medications could interact with this medication?" section for more details.

Heart rhythm: Fosamprenavir can cause a life-threatening irregular heartbeat when taken by someone who is also taking certain medications to control an irregular heart beat. If you are taking lidocaine, amiodarone, or quinidine, make sure your doctor is aware. These medications should not be taken by someone who is also taking fosamprenavir.

Immune reconstitution inflammatory syndrome: This medication may cause immune reconstitution inflammatory syndrome, where signs and symptoms of inflammation from previous infections appear. These symptoms occur soon after starting anti-HIV medication and can vary. They are thought to occur as a result of the immune system improving and being able to fight infections that have been present without symptoms, such as pneumonia, herpes, or tuberculosis. Report any new symptoms to your doctor immediately.

Liver disease: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.

If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

People who also have hepatitis B or C may be more likely to experience liver problems.

Skin allergic reactions: This medication has been associated with a life-threatening skin allergic reaction called Stevens-Johnson syndrome. If you have experienced any skin allergic reactions, tell your doctor before taking this medication. If you experience a severe rash or a rash with accompanying symptoms that affect the body (e.g., fever, nausea), contact your doctor immediately.

Sulfa medication allergy: Fosamprenavir is a sulfonamide (sulfa medication). Some people who are allergic to sulfonamide antibiotics may also experience allergic reactions to fosamprenavir. Before you take fosamprenavir inform your doctor about any previous adverse reactions you have had to medications, especially sulfamethoxazole. Contact your doctor at once if you experience signs of an allergic reaction, such as skin rash, itching, difficulty breathing or swelling of the face and throat.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if fosamprenavir passes into breast milk. Women who have HIV infection are cautioned against breast-feeding because of the risk of passing HIV to a baby who does not have the infection.

Children: The safety and effectiveness of this medication have not been established for children less than 2 years of age.

What other drugs could interact with this medication?

There may be an interaction between fosamprenavir and any of the following:

  • alcohol
  • alpha blockers (e.g., alfuzosin, doxazosin, silodosin, tamsulosin)
  • anti-cancer medications (e.g., cabazitaxel, docetaxel; doxorubicin; etoposide, ifosfamide, irinotecan, vincristine)
  • apixaban
  • aprepitant
  • aripiprazole
  • azole antifungals (e.g., itraconazole, ketoconazole, voriconazole)
  • benzodiazepines (e.g., diazepam, midazolam, triazolam)
  • birth control pills
  • bosentan
  • bromocriptine
  • budesonide
  • buprenorphine
  • buspirone
  • calcitriol
  • calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
  • carbamazepine
  • carvedilol
  • clindamycin
  • cobicistat
  • colchicine
  • conivaptan
  • corticosteroids (e.g., dexamethasone, fluticasone, prednisone)
  • cyclosporine
  • darifenacin
  • deferasirox
  • diabetes medications (e.g., acarbose, canagliflozin, glyburide, insulin, linagliptin, metformin, rosiglitazone)
  • digoxin
  • disopyramide
  • domperidone
  • dronedarone
  • eletriptan
  • enzalutamide
  • eplerenone
  • ergot derivatives (e.g., dihydroergotamine, ergotamine, ergonovine, methylergonovine)
  • eslicarbazepine
  • estrogens (e.g., conjugated estrogen, estradiol, ethinyl estradiol)
  • fentanyl
  • flibanserin
  • garlic
  • grapefruit juice
  • guanfacine
  • H2 antagonists (e.g., famotidine, nizatidine, ranitidine)
  • HIV integrase inhibitors (e.g., dolutegravir, elvitegravir, raltegravir)
  • HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
  • HIV nucleoside reverse transcriptase inhibitors (NRTIs; e.g., abacavir, didanosine, lamivudine, tenofovir, zidovudine)
  • HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
  • ivacaftor
  • ivabradine
  • lemborexant
  • levomilnacipran
  • lidocaine
  • lomitapide
  • lurasidone
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • maraviroc
  • meperidine
  • methadone
  • mifepristone
  • mirabegron
  • modafinil
  • naloxegol
  • nitrates (e.g., isosorbide dinitrate, isosorbide mononitrate)
  • orlistat
  • oxycodone
  • perampanel
  • phenobarbital
  • phenytoin
  • phosphodiesterase-5 inhibitors (e.g., avanafil, sildenafil, tadalafil, vardenafil)
  • pimecrolimus
  • pimozide
  • praziquantel
  • primidone
  • progestins (e.g., dienogest, levonorgestrel, medroxyprogesterone, norethindrone)
  • propafenone
  •  protein kinase inhibitors (e.g., bosutinib, crizotinib, dabrafenib, dasatinib, imatinib, lapatinib, nilotinib, sunitinib)
  • quetiapine
  • quinidine
  • quinine
  • rifabutin
  • rifampin
  • rivaroxaban
  • rupatadine
  • St. John's wort
  • salmeterol
  • selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
  • solifenacin
  • statins or anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
  • tacrolimus
  • ticagrelor
  • tolterodine
  • tolvaptan
  • trazodone
  • ulipristal
  • valproate medications (e.g., sodium divalproex, valproic acid)
  • warfarin
  • zolpidem
  • zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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