Action and Spectrum

Actions and spectrum: 

fosamprenavir is an antiretroviral medication that belongs to protease inhibitors. It is also used as a combination with other antiretroviral drugs to treat human immunodeficiency virus (HIV) infection. 

fosamprenavir works by inhibiting the activity of the HIV-1 protease enzyme, which is responsible for the cleavage of viral polyproteins into their functional components. By inhibiting the protease enzyme, fosamprenavir prevents the formation of mature viral particles and thereby reduces the viral load in the body. 

fosamprenavir has a broad spectrum of activity against HIV-1 strains, including those that are resistant to other protease inhibitors. It is typically used in combination with other antiretroviral medications to achieve optimal viral suppression and delay the development of drug resistance. 

Drug Interaction

Adverse Reaction

Frequency defined 

>10% 

Increased triglycerides (11%) 

Fatigue (11-15%) 

Nausea (30-50%) 

Diarrhea (5-13%) 

Rash (16-20%)  

1-10% 

Abdominal pain (≤ 2%) 

Headache (2-4%) 

Vomiting (2-6%) 

Nausea (3-7%) 

Increased transaminases (4-8%) 

Pruritus (7-8%)  

<1% 

Angioedema 

QT prolongation 

Hypercholesterolemia 

Stevens-Johnson syndrome 

Myocardial infarction 

Nephrolithiasis  

Frequency not defined 

Acute hemolytic anemia 

Diabetes Mellitus 

Spontaneous bleeding 

Immune reconstitution syndrome 

Increased body fat 

Black Box Warning

Black Box Warning: 

fosamprenavir does not have a black box warning in the United States. However, like all HIV medicines, fosamprenavir may cause serious side effects and should be used under the supervision of a healthcare provider.

serious side effects associated with fosamprenavir include liver problems, severe skin reactions, and drug interactions with other medicines. 

Contraindication / Caution

Contraindication/Caution: 

Contraindication: 

fosamprenavir is contraindicated in patients with a known hypersensitivity to the drug or to any of its components. It is also contraindicated in combination with certain medications due to potential drug interactions, such as drugs that are highly dependent on CYP3A4 for clearance, such as alfuzosin, cisapride, colchicine, dronedarone, lovastatin, lurasidone, pimozide, ranolazine, simvastatin, and ergot derivatives such as dihydroergotamine, ergonovine, ergotamine, and methylergonovine.  

Caution: 

• Hepatic Impairment: fosamprenavir should be used with caution in patients with hepatic impairment, as the drug is metabolized by the liver. Patients with severe hepatic impairment should be monitored closely. 
• Renal Impairment: The safety and efficacy of fosamprenavir have not been established in patients with renal impairment. Therefore, fosamprenavir should be used with caution in these patients. 
• Bleeding disorders: fosamprenavir should be used with caution in patients with bleeding disorders or those receiving anticoagulant therapy, as the drug may increase the risk of bleeding. 
• Diabetes: fosamprenavir can cause hyperglycemia, particularly in patients with pre-existing diabetes. Blood glucose levels should be monitored regularly in patients receiving fosamprenavir. 
• QT Prolongation: fosamprenavir may prolong the QT interval, which can lead to serious cardiac arrhythmias. The drug should be used under caution in patients with a history of QT prolongation or those taking medications that can prolong the QT interval. 
• Immune Reconstitution Syndrome: fosamprenavir should be used with caution in patients with advanced HIV infection, as the drug can cause immune reconstitution syndrome. This is a condition in which the patient’s immune system recovers and begins to attack opportunistic infections. 
• Use with Other Medications: fosamprenavir can interact with other medications, including other antiretroviral drugs. Therefore, it is important to inform the healthcare provider about all medications being taken, including prescription, over the counter, and herbal products.

Comorbidities: 

• Hepatic impairment: fosamprenavir is primarily metabolized in the liver, so caution should be exercised when administering this medication to patients with hepatic impairment. 
• Renal impairment: fosamprenavir is excreted by the kidneys, so caution should be exercised when administering this medication to patients with renal impairment. 
• Hyperlipidemia: Protease inhibitors such as fosamprenavir have been associated with an increased risk of hyperlipidemia (elevated levels of fats in the blood). Therefore, lipid levels should be monitored closely in patients taking this medication. 
• Diabetes: Protease inhibitors such as fosamprenavir have an increased risk of insulin resistance and diabetes. Therefore, blood glucose levels should be monitored closely in patients taking this medication. 
• Bleeding disorders: There have been reports of bleeding in patients taking protease inhibitors. Therefore, caution should be exercised when administering fosamprenavir to patients with bleeding disorders or those taking anticoagulant medications. 

Pregnancy / Lactation

Pregnancy consideration: US FDA pregnancy category: Not assigned 

Lactation: It is not known whether fosamprenavir is excreted in human milk  

Pregnancy category: 

• Category A: Satisfactory and well-controlled studies show no risk to the fetus in the first or later trimester. 
• Category B: There is no evidence of risk to the fetus found in animal reproduction studies and there are not enough studies on pregnant women. 
• Category C: Adverse effects on the fetus found with evidence in animal reproduction studies and no adequate evidence for an effect in humans, care must be taken for potential risks in pregnant women. 
• Category D: There is adequate data available with sufficient evidence of human fetal risk from various platforms, but despite potential risks may be used only in emergency cases for potential benefits. 
• Category X: Drugs listed in this category outweigh risks over benefits These category drugs should be prohibited for pregnant women. 
• Category N: There is no data available for the drug under this category. 

Pharmacology

Pharmacology: 

fosamprenavir is an antiviral medication belonging to the class of protease inhibitors. It works by inhibiting the protease enzyme of the human immunodeficiency virus (HIV), which is essential for viral replication. fosamprenavir is a prodrug that is metabolized into its active form, amprenavir, in the body. 

fosamprenavir is a reversible inhibitor of the HIV-1 and HIV-2 proteases. It binds to the active site of the protease, preventing the cleavage of viral polyproteins into their individual functional proteins. This results in the production of non-infectious viral particles. 

fosamprenavir has a broad spectrum of activity against HIV-1 and HIV-2. It is active against HIV strains resistant to other protease inhibitors, and it has been shown to be effective against both wild-type and multi-drug-resistant strains of HIV.  

Pharmacodynamics: 

fosamprenavir is a protease inhibitor that works by inhibiting the HIV-1 protease enzyme, which is essential for the replication of the virus. By doing so, it prevents the cleavage of the viral polyprotein precursors, resulting in the formation of immature, non-infectious virions. 

fosamprenavir exhibits concentration-dependent antiviral activity against HIV-1. It has been effective against both wild-type and drug-resistant strains of HIV-1. 

In addition, fosamprenavir has also been shown to reduce the viral load and increase CD4 cell counts in patients infected with HIV-1.  

Pharmacokinetics: 

Absorption 

fosamprenavir is administered orally as the calcium salt. It is rapidly absorbed from the GIT and converted to amprenavir by hydrolysis. The bioavailability of fosamprenavir is approximately 90%, and the maximum plasma concentration (Cmax) is achieved within 2-4 hours after oral administration. 

Distribution 

fosamprenavir is extensively distributed into tissues, including the liver, spleen, lymph nodes, and brain. The protein binding of amprenavir is moderate, with approximately 90% bound to plasma proteins. 

Metabolism 

fosamprenavir is primarily metabolized in the liver by the cytochrome P450 (CYP) enzyme system, CYP3A4. fosamprenavir is also a weak inhibitor of CYP3A4, and it may interact with other drugs that are metabolized by this enzyme system. 

Elimination and excretion 

fosamprenavir is primarily metabolized in the liver by the cytochrome P450 (CYP) enzyme system, CYP3A4. fosamprenavir is also a weak inhibitor of CYP3A4, and it may interact with other drugs that are metabolized by this enzyme system. 

Adminstartion

Administration: 

fosamprenavir is administered orally in the form of tablets or oral suspension. The tablets are available in 700 mg strength and the oral suspension is available as 50 mg/mL and 100 mg/mL. The dose and frequency of administration depend on the patient’s age, weight, renal function, and concomitant medications.

It is recommended to be taken with or without food, but high-fat meals should be avoided as it may decrease the absorption of the drug. It is important to follow the prescribed dosing regimen to ensure optimal therapeutic effect and minimize the risk of adverse effects. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: fosamprenavir 

Pronounced: [ FOS-am-PREN-a-veer]  

Why do we use fosamprenavir ? 

fosamprenavir is a medication used in the treatment of HIV infection. It is typically used in combination with other antiretroviral drugs as part of a regimen known as highly active antiretroviral therapy (HAART) to slow the progression of the disease and to improve the patient’s quality of life.

fosamprenavir is a protease inhibitor, which work by blocking the activity of an enzyme called HIV protease that is necessary for the virus to replicate. By inhibiting this enzyme, fosamprenavir helps to prevent from multiplying and spreading throughout the body.