Fosamprenavir

Fosamprenavir is a prescription medication used to treat HIV, which causes acquired immunodeficiency syndrome (AIDS).

• Fosamprenavir is available under the following different brand names: Lexiva.

Common side effects of Fosamprenavir include:

• diarrhea
• nausea
• vomiting
• headache
• fatigue
• stomach or abdominal pain
• numbness or tingling (especially around the mouth)
• headache
• mood changes
• changes in the shape or location of body fat (especially in the arms, legs, face, neck, breasts, and waist)

Serious side effects of Fosamprenavir include:

• hives
• difficulty breathing
• swelling of the face, lips, tongue, or throat
• fever
• sore throat,
• burning eyes
• skin pain
• red or purple skin rash with blistering and peeling
• pale or yellow skin
• dark-colored urine
• confusion
• weakness
• increased urination
• extreme thirst
• dry mouth
• fruity breath odor
• sudden and severe pain in the lower back or side
• blood in your urine
• pain or burning while urinating
• night sweats
• swollen glands
• cold sores
• cough
• wheezing
• diarrhea
• weight loss
• trouble speaking or swallowing
• problems with balance or eye movement
• prickly feeling
• swelling in the neck or throat (enlarged thyroid)
• menstrual changes
• impotence

Rare side effects of Fosamprenavir include:

• none

Seek medical care or call 911 at once if you have the following serious side effects:

• Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, coordination loss, unsteady, very stiff muscles, high fever, profuse sweating, or tremors.
• Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.
• Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

Adult and pediatric dosage

Tablet

• 700 mg

Oral suspension

• 50 mg/mL

HIV Infection

Adult dosage

• Therapy-naive patients
  • 1400 mg orally every 12 hours (without ritonavir)
  • 1400 mg orally once a day (with ritonavir 100-200 mg once a day)
  • 700 mg orally every 12 hours (with ritonavir 100 mg every 12 hours)
• Protease inhibitor-experienced patients
  • 700 mg orally every 12 hours (with ritonavir 100 mg every 12 hours)
• Coadministration with efavirenz
  • 700 mg orally every 12 hours (with ritonavir 100 mg every 12 hours) plus 600 mg efavirenz once a day, or
  • 1400 mg orally once a day (with ritonavir 300 mg once a day) plus 600 mg efavirenz once a day
• Combination with maraviroc
  • 700 mg orally every 12 hours (with ritonavir 100 mg every 12 hours) plus maraviroc 150 mg orally every 12 hours
  • Pregnant women on fosamprenavir plus ritonavir
  • 700 mg orally every 12 hours (with ritonavir 100 mg every 12 hours)
  • Lower exposures of amprenavir (active moiety) observed during pregnancy; therefore, closely monitor viral load to ensure viral suppression is maintained

Pediatric dosage

• Protease inhibitor-naive patients
  • Children aged below 4 weeks: Safety and efficacy not established.
  • For infants, use only in those born at 38 weeks gestation or greater and who have attained a postnatal age of 28 days.
  • Children weighing below 11 kg: 45 mg/kg orally every 12 hours plus ritonavir 7 mg/kg every 12 hours.
  • Children weighing 11 to 14 kg: 30 mg/kg orally every 12 hours plus ritonavir 3 mg/kg every 12 hours.
  • Children weighing 15 kg to 19 kg: 23 mg/kg orally every 12 hours plus ritonavir 3 mg/kg every 12 hours.
  • Children weighing 20 kg and more: 18 mg/kg orally every 12 hours plus ritonavir 3 mg/kg every 12 hours.
  • NOTE: Do not exceed the adult dose of 700 mg/ritonavir 100 mg every 12 hours when dosing with ritonavir.
  • Alternatively, protease inhibitor-naive children aged ≥2 years may be administered 30 mg/kg orally every 12 hours (without ritonavir)
• Unboosted regimen
  • Children aged below 2 years: Not recommended without ritonavir.
  • Children aged 2 years and older and weighing below 47 kg: 30 mg/kg/dose orally every 12 hours; not to exceed 1400 mg orally every 12 hours.
  • Children aged 2 years and older and weighing 47 kg and more: 1400 mg orally every 12 hours.
• Protease inhibitor-experienced patients
  • Children aged below 6 months: Safety and efficacy not established.
  • Children aged 6 months and older.
  • Children weight below 11 kg: 45 mg/kg/dose orally every 12 hours; not to exceed 700 mg Fosamprenavir/100 mg ritonavir orally every 12 hours.
  • Children weight between 11-15 kg: 30 mg/kg/dose orally every 12 hours plus 3 mg/kg/dose ritonavir orally every 12 hours; not to exceed 700 mg Fosamprenavir/100 mg ritonavir orally every 12 hours.
  • Children weight 15 to 19 kg: 23 mg/kg/dose orally every 12 hours plus 3 mg/kg/dose ritonavir orally every 12 hours; not to exceed 700 mg Fosamprenavir/100 mg ritonavir orally every 12 hours.
  • Children weighing 20 kg and more: 18 mg/kg/dose orally every 12 hours plus 3 mg/kg/dose ritonavir orally every 12 hours; not to exceed 700 mg Fosamprenavir/100 mg ritonavir orally every 12 hours.

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, healthcare provider, or pharmacist first.

• Fosamprenavir has severe interactions with at least 24 other drugs.
• Fosamprenavir has serious interactions with at least 129 other drugs.
• Fosamprenavir has moderate interactions with at least 284 other drugs.
• Fosamprenavir has minor interactions with at least 48 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, health questions, or concerns.

Contraindications

• Hypersensitivity (eg, Stevens-Johnson syndrome) to Fosamprenavir, amprenavir, or another component
• Concomitant use of drugs that depend heavily on CYP3A4 for clearance; metabolite amprenavir is a strong CYP3A4 inhibitor; use with ritonavir, another strong CYP3A4 inhibitor, may have additive inhibitory effects; check Drug Interactions
• Drugs that are contraindicated with Fosamprenavir (with or without ritonavir) include lipid modifying agents (eg, Lomitapide, Lovastatin, Simvastatin), alpha1-adrenoreceptor agonists (. eg, alfuzosin), antiarrhythmics (flecainide, propafenone), rifampin, ergot derivatives (dihydroergotamine, ergonovine, ergotamine, methylergonovine), cisapride, St. John’s wort, lurasidone, pimozide, sildenafil (when used for pulmonary arterial hypertension), midazolam, and triazolam

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Fosamprenavir?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Fosamprenavir?”

Cautions

• New onset DM, exacerbation of preexisting DM & hyperglycemia reported with unknown frequency/unknown causal relationship
• Sulfonamide allergy
• Monitor labs before and during treatment with Hepatitis B or C, or elevated transaminases
• Few reports of spontaneous bleeding in patients. with Hemophilia A and B
• During initial treatment, inflammatory response to indolent or residual opportunistic infections may occur and require treatment
• Fat redistribution with "cushingoid appearance" and "buffalo hump" may occur
• Increased risk for myocardial infarction (thought to be caused by protease inhibitors increasing the risk of hyperlipidemia)
• Monitor triglycerides and cholesterol levels before initiating; then periodically initiate clinical management of lipid disorders, as required
• Combination treatment with ritonavir may lead to increased triglyceride levels
• Unknown effect on the activity of subsequently administered protease inhibitors
• Risk for immune reconstitution syndrome if used in combination with other antiretroviral drugs; autoimmune disorders (eg, Graves disease, polymyositis, and Guillain-Barré syndrome), have also been reported to occur in the setting of immune reconstitution; however, the time to onset is more variable and can occur many months after initiation of treatment.
• Vomiting is more common in children
• Cases of nephrolithiasis reported with fosamprenavir
• Acute hemolytic anemia reported with amprenavir
• Discontinue therapy if severe skin reactions (such as Stevens-Johnson syndrome) occur

Pregnancy and Lactation

• Pregnancy Registry: To monitor maternal-fetal outcomes of pregnant women exposed to antiretroviral medications, call 1-800-258-4263 or visit www.APRegistry.com
• There are insufficient prospective pregnancy data from the Antiretroviral Pregnancy Registry (APR) to adequately assess the risk for adverse developmental outcomes; the use of Fosamprenavir during pregnancy has been evaluated in a limited number of women as reported by the APR; available data from the APR show two birth defects in 109 first trimester exposures and 2 birth defects in 36 second and third trimester exposures compared with the background rate for major birth defects of 2.7% in a US reference population of the Metropolitan Atlanta Congenital Defects Program. 
• Limited data are available on the drug’s use during pregnancy; Fosamprenavir 700 mg two times a day with ritonavir 100 mg two times a day should only be considered in pregnant patients who have already been on a stable Fosamprenavir/ritonavir regimen before pregnancy, and who are virologically suppressed (HIV-1 RNA below 50 copies/mL)
• Contraception
  • Fosamprenavir may reduce the efficacy of combined hormonal contraceptives; advise patients to use an effective alternative contraceptive method or an additional barrier method of contraception
• Lactation
  • There is no information available on the presence of amprenavir in human milk, the effects of the drug on breastfed infants, or milk production
  • The CDC recommends that mothers infected with HIV1 in the US should not breastfeed their infants to avoid risking postnatal transmission of HIV-1 infection