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Fosamprenavir

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Fosamprenavir, Fosamprenavir/r, Lexiva, FPV, FPV/r

  • See Also
  1. Anti-Retroviral Therapy
  2. Protease Inhibitor
  • Indications
  1. HIV Infection (as part of combination therapy)
  • Contraindications
  1. Sulfonamide Allergy (Exercise caution if used)
  2. Age <6 months (per HIV Treatment guidelines)
  • Mechanism
  1. See Protease Inhibitor
  2. Fosamprenavir is a prodrug, metabolized in vivo to amprenavir (Agenerase)
  3. Amprenavir is a synthetic derivative of hydroxyethylamine Sulfonamide, a Protease Inhibitor
  • Medications
  1. Fosamprenavir is typically taken with Ritonavir (Fosamprenavir/r)
    1. Unboosted Fosamprenavir is not typically recommended
    2. All adverse effects and Drug Interactions on this page assume administration with Ritonavir
  2. Tablets: 700 mg
    1. May take with or without food
  3. Suspension: 50 mg/ml
    1. Take with food (and better tolerated when refrigerated)
  • Dosing
  • Adult
  1. General
    1. Repeat dose if patient vomits within 30 minutes of dose
    2. HIV Treatment guidelines recommend only twice daily dosing regimen
      1. Package insert also describes once daily dosing in treatment naive patients (not listed here due to guidelines)
  2. Standard Dose
    1. Fosamprenavir 700 mg orally twice daily AND
    2. Ritonavir 100 mg orally twice daily
  3. Reduced Dose in Hepatic Dysfunction (adults only, pediatric doses not affected)
    1. Mild hepatic dysfunction (Child-Pugh Score 5 to 6)
      1. Fosamprenavir 700 mg orally twice daily AND
      2. Ritonavir 100 mg orally ONCE daily
    2. Moderate hepatic dysfunction (Child-Pugh Score 7 to 9)
      1. Fosamprenavir 450 mg orally twice daily AND
      2. Ritonavir 100 mg orally ONCE daily
    3. Severe hepatic dysfunction (Child-Pugh Score >9)
      1. Fosamprenavir 300 mg orally twice daily AND
      2. Ritonavir 100 mg orally ONCE daily
  • Dosing
  • Child (age >6 months)
  1. General
    1. Repeat dose if patient vomits within 30 minutes of dose
    2. Take suspension with food (but tablets with or without food)
  2. Weight <11 kg: Fosamprenavir 45 mg/kg and Ritonavir 7 mg/kg, both taken orally twice daily
  3. Weight 11 to 15 kg: Fosamprenavir 30 mg/kg and Ritonavir 3 mg/kg, both taken orally twice daily
  4. Weight 15 to 20 kg: Fosamprenavir 23 mg/kg and Ritonavir 3 mg/kg, both taken orally twice daily
  5. Weight >20 kg: Fosamprenavir 18 mg/kg and Ritonavir 3 mg/kg, both taken orally twice daily
  6. Maximum (adult dose)
    1. Fosamprenavir 700 mg (weight >39 kg) orally twice daily AND
    2. Ritonavir 100 mg (weight >33 kg) orally twice daily
  • Adverse Effects
  1. See Protease Inhibitor for adverse effects attributed to the class
  2. Perioral Paresthesias
  3. Hyperlipidemia
    1. Monitor lipid panel at baseline and periodically
  4. Rash (19%)
    1. Stevens-Johnson Syndrome risk
    2. Severe in some cases
  • Safety
  1. Avoid in Lactation
  2. Unknown safety in pregnancy (avoid)
  • Drug Interactions
  1. Multiple Drug Interactions as a CYP3A4 inhibitor
    1. See Protease Inhibitor
    2. As with other Protease Inhibitors, check a formal Drug Interaction application before prescribing
  2. Aluminum Hydroxide and Magnesium Hydroxide Antacid
    1. Reduced Fosamprenavir absorption
  3. Statins (esp. Atorvastatin)
    1. Limit to lowest effective dose (Atorvastatin 20 mg/day)
  4. Rifabutin
    1. Monitor Complete Blood Count (baseline and weekly)
  5. Tricyclic Antidepressants
    1. Monitor levels
  6. Immunosuppressants
    1. Monitor levels
  7. Methadone
    1. Fosamprenavir may reduce Methadone effectiveness (may require higher Methadone doses)
  8. Azole Antifungals (esp. Ketoconazole, Itraconazole)
    1. Limit to low dose (e.g. ketonazole 200 mg)
  9. Vardenafil
    1. Limit Vardenafil dose to 2.5 mg/day
  10. Oral Contraceptives
    1. Use other forms of Contraception instead
  • Resources
  1. Fosamprenavir (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3a1424d8-844c-4e24-9ebd-b2c2b61b61a3
  • References
  1. (2009) Treat Guidel Med Lett 7(78): 11-22 [PubMed]
  2. Reust (2011) Am Fam Physician 83(12): 1443-51 [PubMed]