Fosamprenavir (Oral)

While it cannot cure HIV, fosamprenavir can slow down and prevent the spread of the HIV virus, and hopefully prevent the onset of AIDS in a patient being treated.


Fosamprenavir can be used to treat both adult patients, and pediatric patients who are at least four weeks old, for the purpose of reducing the spread of HIV, and ideally to halt it altogether before it has a chance to cause AIDS in the patient. It is an anti-viral medication which prevents the spread of the HIV virus and is one of the most potent weapons against the onset of AIDS in the medical arsenal.

It is extremely important that this medication is taken exactly as prescribed, and that no dosages should be missed, because that may provide an opportunity to the HIV virus to become more resistant to treatment, and that can be problematic for the patient. It should be taken with a glass of water, with or without food, according to patient preference, but it should always be at regular intervals as directed on the label.

Even when a patient begins to feel better, the routine established for regular dosing should not be interrupted, so that the medication has a chance to be as effective as possible. When dosages are forgotten or skipped, it is advisable to return to the dosage schedule at the earliest opportunity and to avoid future mishaps with dosing.

The medication is available in a liquid suspension form and in tablet form, and the one which your doctor prescribes for you will depend partly on your own preferences, as well as which is more commonly available in your location. In either case, the medication has the same level of effectiveness and can be relied upon for the reduction of symptoms in treating HIV.

Condition Treated

  • Prevents spread of HIV in the body

Type Of Medicine

  • Anti-viral

Side Effects

Along with the beneficial effects delivered by fosamprenavir, there are also some less desirable side effects which many patients experience, to a greater or lesser degree. While some patients may experience no side effects at all when using this medication, others incur side effects which are uncomfortable enough that they require treatment by a medical professional.

In some very unusual cases, patients have an allergic reaction to fosamprenavir, and this is one of the situations where medical attention may be necessary immediately. Because an allergic reaction has the potential to produce symptoms in a patient that may become life-threatening, medical attention should be sought out at the very earliest opportunity, so as to avoid an emergency. The most common side effects which are recognized in the event of an allergic reaction are any of those included among the following:

  • Hives and or rashes appearing on the skin at various locations around the body
  • Extreme itchiness
  • Difficulty with breathing, sometimes accompanied by severe tightness in the chest
  • Lightheadedness or dizziness
  • Puffiness or swelling in the area of the face, particularly in the eyelids, throat, lips, and tongue.

Some of the more common side effects experienced by patients being treated with this medication include the following:

  • Nausea and/or vomiting
  • Profuse sweating
  • Blurry vision or other vision problems
  • Dry mouth
  • Increased urination and increased urgency to urinate
  • Increase in appetite
  • A fruit-like odor on the breath
  • Skin which is flushed and/or dry
  • Mood swings or mental changes
  • Unexplained weight loss
  • Uncharacteristic weakness or tiredness
  • Abdominal pain or cramping
  • Stomach pain or cramping
  • Severe skin rashes.

The side effects listed in the group below have only rarely been reported by patients being treated with fosamprenavir, but you should be on the lookout for these anyway, since there is a potential for their occurrence, and in some unusual cases, they have even been reported as very severe.

  • Yellowish tinge to the skin, or around the eyes
  • Lesions on the skin which are colored red, but which sometimes have a purplish color in the center
  • Swelling at various locations around the body
  • Pains in the stomach, back, or legs
  • Bleeding gums
  • Eyes being watery or generally irritated
  • Sore throat
  • Paleness of the skin
  • Nosebleeds
  • Loss of appetite
  • Peeling, loosening, or blistering of the skin
  • Persistent coughing
  • Shallow breathing or other breathing difficulties
  • Fevers
  • Extreme itchiness
  • White spots, ulcers, or sores appearing either on the lips or inside the mouth
  • Urine which is dark-colored
  • Very large swellings which appear to be hive -like, and are manifested on the tongue, throat, hands, eyelids, sex organs, legs, lips, or feet.

In addition to those side effects listed above, there is another class of very minor side effects which affect very few patients, and which do not persist more than a few hours, or for a day after their initial appearance. This class of side effects will generally subside and disappear all on their own, without the need for any medical attention at all. As your body adjusts itself to the medication be administered, these side effects tend to fade away and do not return.

  • Rashes which are mild or moderate in severity, and quickly subside
  • A tingling or burning sensation in the lips or around the mouth area in general
  • Minor headaches
  • Fatty deposits appearing on the neck, face, or trunk area
  • Temporary breast enlargement
  • Swelling of the ankles, feet, or lower legs.


Dosages shown below should not be considered universal for all cases, and are only meant to be understood as a standard level of dosage. Your own dosage level may vary from the standard either up or down, per your doctor's recommendation. The actual dosage prescribed for any specific patient will depend on several factors, including the strength of the medication itself, the frequency for which it is administered, the total duration of the program of treatment, your body's tolerance to the medication, and your personal medical condition at the time of treatment. If you have any other medical conditions, diseases, or issues which might interfere or impact the medication being delivered, that will also be taken into account by your medical professional before a dosage level is arrived at.

An adult who is being treated for HIV infection might expect dosage in the following range:

  • If administered in standalone fashion, 1400 mg of fosamprenavir twice each day
  • If administered in tandem with ritonavir, 1400 mg of fosamprenavir along with 200 mg of ritonavir, taken once a day orally
  • An alternative to the 1400/200 fosamprenavir/ritonavir combination might be 1400 mg of fosamprenavir plus 100 mg of ritonavir taken orally once a day
  • Another alternative to the 1400/200 tandem drug administration would be 700 mg of fosamprenavir, taken with 100 mg of ritonavir once a day via the oral route
  • For patients experienced with protease inhibitors, 700 mg of fosamprenavir plus 100 mg of ritonavir, administered orally twice each day.

A standard adult dosage for non-occupational exposure, which has not been explicitly approved by the FDA:

  • The recommendation of the Center for Disease Control and Prevention is 1400 mg of fosamprenavir taken orally twice a day
  • The duration of this treatment is set at a standard 28 days
  • Within 72 hours of non-occupational exposure, prophylaxis should be initiated
  • Alternative programs of treatment for non-occupational exposure HIV prophylaxis calls for fosamprenavir to be included as part of a protease inhibitor based program.

Standard pediatric dosages for HIV infection include the following considerations:

  • When administered in standalone fashion with no ritonavir, patients who are protease inhibitor naïve and are two years old or above would take a standard dosage of oral suspension liquid at 30 mg per kilogram of weight, twice each day, up to a maximum of a 1400 mg dosage
  • For the same profile patient being administered a tablet, and who is at least 47 kg or more, the dosage would be 1400 mg taken orally twice each day
  • When fosamprenavir is administered in tandem with ritonavir, for patients who are protease inhibitor naïve and are at least four weeks of age, the oral suspension dosage at less than 11 kg would be 45 mg per kilogram of weight of fosamprenavir, in addition to 7 mg per kilogram of ritonavir, administered twice each day orally
  • For the same pediatric profile patient weighing between 11 and 15 kg, dosage would be 30 mg per kilogram of weight of fosamprenavir plus 3 mg per kilogram of ritonavir administered twice each day orally
  • For the same pediatric profile patient weighing between 15 and 20 kg, the dosage would be 23 mg per kilogram of weight of fosamprenavir plus 3 mg per kilogram of weight of ritonavir, administered twice a day orally
  • For the same profile patient weighing 20 kg or more, the dosage would be 18 mg per kilogram of weight of fosamprenavir in addition to 3 mg per kilogram of ritonavir, with ceilings of the respective medications at 700 mg and 100 mg
  • For the same profile patient being administered a tablet form of the medication, a patient weighing 39 kg or more would receive a dosage of 700 mg of fosamprenavir plus 100 mg of ritonavir administered twice each day orally
  • For pediatric patients who are protease inhibitor experienced and are at least six months of age, the oral suspension form dosage at less than 11 kg would be 45 mg per kilogram of fosamprenavir plus 7 mg of ritonavir per kilogram administered orally twice a day
  • For the same profile patient weighing between 11 and 15 kg, the dosage would be 30 mg per kilogram of fosamprenavir plus 3 mg per kilogram of ritonavir, delivered twice each day orally
  • For the same profile patient weighing between 15 to 20 kg, the standard dosage would be 23 mg per kilogram of fosamprenavir, in addition to 3 mg per kilogram of ritonavir administered twice each day orally
  • For the same profile patient weighing 20 kg or more the standard dosage would be 18 mg per kilogram of fosamprenavir in addition to 3 mg per kilogram of ritonavir, administered orally twice each day, with ceiling dosages of the respective medications set at 700 mg and 100 mg
  • For the same profile patient being administered the tablet form of the medication and who weighs 39 kg or more, a standard dosage would be 700 mg of fosamprenavir plus 100 mg of ritonavir, administered twice each day orally.


As with most medications, there is a potential for fosamprenavir to interact with other drugs, and these interactions may cause adverse side effects to the patient, or they may diminish the effectiveness of either or both medications.

For this reason, it is strongly recommended that the patient being considered for treatment with fosamprenavir prepare a full list of all medications currently being taken, including other prescription medications, vitamins, herbal supplements, and over-the-counter drugs, as well as all the dosages of each of these.

This list will be an important document to have on hand if it becomes necessary to visit an emergency room for treatment. Any doctors in residence at the emergency room would not be able to safely treat your medical condition unless they knew which medications you are already taking, so they can avoid any drug interactions.

Some of the drugs which are most frequently checked by doctors for potential interaction with fosamprenavir are included in the list below:

  • St. John's wort
  • Pimozide
  • Dihydroergotamine
  • Ergonovine
  • Alfuzosin
  • Rifampin
  • Ergotamine
  • Methylergonovine
  • Cizapride
  • Midazolam
  • Lovastatin
  • Triazolam
  • Simvastatin
  • Delavirdine
  • Sildenafil
  • Flecainide
  • Propafenone
  • Any other drugs used to treat HIV or AIDS
  • Medications to lower cholesterol
  • Any medications which treat high blood pressure
  • Antibiotics
  • Antifungal medications
  • Antidepressants or antipsychotic medications
  • Blood thinners such as Coumadin, warfarin, or Jantoven
  • Organ transplant rejection medications
  • Drugs which treat breathing disorders
  • Medications for the treatment of nausea and vomiting
  • Antiviral medications for the treatment of hepatitis C
  • Any type of narcotic medication
  • Corticosteroids
  • Medications which reduce stomach acid
  • Medicines for the treatment of seizures or convulsions
  • Sedatives
  • Medications for breathing disorders
  • Medications for the treatment of erectile dysfunction.


There are a number of precautions and warnings associated with the administration of fosamprenavir to patients, and these will need to be observed by both doctor and patient, so as not to create any greater risk for the patient than the benefit which is provided. In some cases, severe and even life-threatening skin reactions have occurred in patients who have been treated with fosamprenavir. This includes at least one instance of Stevens-Johnson Syndrome, and it is possible that others have also occurred. Treatment with fosamprenavir should be immediately halted if any rash attributable to its medication is considered to be severe, or is associated with symptoms that are systemic in nature.

During the post-marketing experience with protease inhibitors, there have been reports of new onset diabetes mellitus, exacerbation of pre-existing diabetes mellitus, hyperglycemia, and ketoacidosis have occurred. Although a causal relationship has not been definitively established, it is well to keep these occurrences in mind and to have a careful monitoring of glucose levels in the bloodstream. It may also be necessary to initiate insulin treatment or adjust dosages of insulin or other hypoglycemic agents, during treatment with fosamprenavir.

Some hemophiliac patients have experienced spontaneous bleeding episodes during the reception of protease inhibitors, and while a causal relationship with fosamprenavir has not been definitively established, it's better to be cautious and monitor a hemophiliac patient who is undergoing protease inhibitor therapy.

Since therapy involving fosamprenavir and ritonavir has been linked to increased levels of cholesterol and triglycerides, it is highly recommended that testing for both these components be initiated prior to treatment, as well as periodically during ongoing treatment with fosamprenavir.

If necessary, lipid disorders should also be monitored and managed as needed.

Controlled case studies have demonstrated an increased risk of myocardial infarction in patients being treated with fosamprenavir or amprenavir. It is therefore highly advisable to monitor HIV-infected patients with a particular view toward lipid disorders, hypertension, diabetes mellitus and smoking, since these are risk factors which can be managed to reduce the risk of cardiovascular disease.

During combination antiretroviral therapy, there have been instances reported of immune reconstitution syndrome, and patients may exhibit inflammation as part of their response to residual opportunistic infections. These may then require evaluation, and some type of medical treatment for remediation.

Also observed in a number of patients during antiretroviral therapy have been some of the following occurrences, which make it important to monitor a patient for any physical signs that fat redistribution has occurred or is occurring:

  • Breast enlargement
  • Wasting of the facial area
  • Peripheral wasting
  • Redistribution of body fat
  • Accumulation of body fat
  • Dorsocervical fat enlargement
  • Central obesity
  • Cushingoid appearance.

Patients who have hepatic impairment may experience increased amprenavir concentrations, which makes it important that caution is observed when treating such patients. People who have underlying hepatitis B or hepatitis C may be more susceptible to developing transaminase elevations, or to having this condition exacerbated by treatment with fosamprenavir. It is highly advisable to closely monitor liver functions during treatment for this reason.

It is also recommended that maximum levels of fosamprenavir and ritonavir be avoided as much as possible because of the potential for transaminase elevations to occur. If signs or symptoms of nephrolithiasis appear in any patient being treated, it is strongly recommended that fosamprenaivr be immediately discontinued as a treatment program, or at the very least temporarily interrupted.

It is recommended that fosamprenavir always be used in tandem with other antiretroviral agents.

Although it has not been fully explored or researched, there is a potential for HIV cross resistance to occur among protease inhibitors. It is not currently known whether there is any effect on the activity of protease inhibitors by fosamprenavir therapy. Exactly which antiretroviral agents are prescribed for any given patient's treatment program must be carefully considered, generally in close consultation with an expert on infectious diseases.

It is not recommended that the adult protease inhibitor experienced patient be given single daily dosages of fosamprenavir plus ritonavir, nor is it advisable for pediatric patients. It is not recommended that dosing with fosamprenavir without ritonavir be used more than once a day in pediatric patients under the age of two. For protease inhibitor experienced pediatric patients who are less than six months of age, it is not recommended that fosamprenavir be administered either in standalone mode or with ritonavir.

The safety and effectiveness of fosamprenavir has not been clearly established for pediatric patients who are younger than four weeks of age, so it should only be administered to infants who have experienced at least 38 weeks of gestation and have achieved a postnatal age of at least 28 days.

Since medication dosage for pediatric patients is almost always dependent on the child's weight, it is very important for a parent or guardian to report any changes in weight for a child being treated with fosamprenavir, whether it is accompanied by ritonavir or not. Also important for pediatric patients is the dosage preparation, if using the oral suspension form of the medication. In these situations, fosamprenavir should be well shaken just prior to administration, and should then be delivered via a dosing spoon or cup, so that precise measurements can be administered.


Fosamprenavir should be stored in a location which is maintained at a temperature between 60 degrees Fahrenheit and 86 degrees Fahrenheit, although temporary excursions up or down are permissible. Excessive humidity is also to be avoided since this can degrade the medication and reduce its effectiveness. For this reason, storing the medication in a bathroom is not advisable, since this is an area subject to elevated levels of moisture, especially during bathing and showering times.

This drug should be stored in a location well out of the reach of all pets and children, ideally in a spot which cannot be reached, even if a child were to stand on furniture. The containers used as weekly pill reminders are bad locations for this medication or any other one to be stored because they simply cannot prevent access in the manner that they should. With no locking mechanisms to keep out curious children or others, any pills stored in such containers can easily be accessed, and problems can ensue.

If you should have unused fosamprenavir in the house, or if it expires before it can be used, you should dispose of it according to instructions given you by your doctor or pharmacist, and should not be flushed down a toilet or sink. Lacking the appropriate guidelines for proper disposal, you can consult the FDA website which is maintained to provide guidance for safe disposal of medicines. It should always be borne in mind that you need to avoid the possibility of this medication causing a danger to any pets, children, or other household members because it hasn't been handled properly.


The main treatment purpose for fosamprenavir is to halt the spread of human immuno-deficiency virus (HIV) before it can overtake the body and settle in to cause AIDS. This medication is available by prescription only and must be recommended by your doctor for treatment. It can be prescribed for both adult patients and for pediatric patients, although infant patients should have been in gestation for at least 38 days, and should have achieved a post-natal age of at least 28 days prior to treatment.

There are a considerable number of side effects which are possible when being treated with fosamprenavir, and there is also a likelihood of interaction with other drugs, so great care must be taken when any other form of medication is being concurrently given to a patient. Since potential side effects have the potential to be fairly severe, patients must be closely monitored, both for observable signs and sometimes also for blood levels.

It is very important that all of a prescribed treatment program be taken by a patient because there is a possibility that the HIV virus may become more resistant to treatment, if a patient stops short of the full treatment program, or changes the dosage in any way.