FOSAMPRENAVIR CALCIUM
| FOSAMPRENAVIR CALCIUM (fos-am-pre'na-vir) Lexiva Classifications: antiretroviral agent; protease inhibitor; Therapeutic: antiretroviral; protease inhibitor Prototype: Saquinavir Pregnancy Category: C |
Availability
700 mg tablet
Action
Fosamprenavir is a prodrug rapidly converted to amprenavir. Amprenavir is an HIV-1 protease inhibitor that binds to the active site of HIV-1 protease. Binding prevents processing of viral Gag and Gag-Pol polyprotein precursors, resulting in formation of immature noninfectious viral particles.
Therapeutic Effect
Inhibits normal replication of the HIV virus rending the virus noninfectious.
Uses
Treatment of HIV infection in combination with other antiretroviral agents.
Contraindications
Hypersensitivity to amprenavir; ergot derivatives, pimozide, midazolam, triazolam; coadministration of ritonavir, flecainide, and propafenone; severe hepatic impairment; pregnancy (category C), lactation. Safety and efficacy in children <18 y have not been established.
Cautious Use
Sulfonamide allergy; mild to moderate hepatic impairment; elderly; hemophilia.
Route & Dosage
| HIV Infection Adult: PO 700 mg b.i.d. in combination with 100 mg ritonavir b.i.d. (preferred if previously on a protease inhibitor); or 1400 mg b.i.d.; or 1400 mg q.d. in combination with 200 mg ritonavir q.d. Mild to Moderate Hepatic Impairment Reduce dose to 700 mg b.i.d. without ritonavir; not recommended in severe hepatic impairment. |
Administration
Oral- Ensure that patient is not receiving drugs contraindicated with fosamprenavir.
- Store at 15°–30° C (59°–86° F) in a tightly closed container.
Adverse Effects (≥1%)
Body as a Whole: Fatigue. CNS: Oral/perioral paresthesia, peripheral paresthesia, depression, mood disorders. GI: Nausea, vomiting, diarrhea, abdominal pain, taste disorders, increased triglycerides, and hyperglycemia. Skin: Rash, pruritus, Stevens-Johnson syndrome.Interactions
Note: Interaction profile can be significantly affected by coadministration with ritonavir. Drug: Administration with amiodarone, bepridil, dihydroergotamine, ergotamine, flecainide, itraconazole, ketoconazole, lidocaine, midazolam, pimozide, propafenone, quinidine, triazolam, and tricyclic antidepressants may cause life-threatening reactions; rifampin, rifabutin, oral contraceptives, phenobarbital, phenytoin, carbamazepine decrease amprenavir concentrations; amprenavir may increase dihydroergotamine, ergotamine, sildenafil concentrations and toxicity; amprenavir may decrease methadone levels; monitor INR with warfarin; increased risk of myopathy and rhabdomyolysis with lovastatin, simvastatin; may decrease antiviral effectiveness of delavirdine or lopinavir/ritonavir. Herbal: St. John's wort may decrease antiretroviral activity.Pharmacokinetics
Absorption: Prodrug is rapidly hydrolyzed to amprenavir (active component) by gut enzymes during absorption. Peak: 2.5 h. Metabolism: In liver by CYP3A4. Elimination: 14% in urine, 75% in feces. Half-Life: 7.7 h.Nursing Implications
Assessment & Drug Effects
- Ensure that patient has provided a complete list of all prescription, nonprescription, or herbal drugs being used.
- Monitor closely diabetics for loss of glycemic control.
- Monitor males taking PDE5 inhibitors for erectile dysfunction for adverse events including hypotension, visual changes, and priapism. Report promptly.
- Lab test: Baseline and periodic LFTs; periodic lipid profile; periodic blood glucose.
Patient & Family Education
- If you miss a dose by >4 h, wait and take the next dose at the regular time.
- Do not take other prescription, nonprescription, or herbal drugs without consulting physician.
- Monitor blood glucose more often than usual if diabetic.
- To prevent pregnancy, use a barrier contraceptive in addition to hormonal contraception.
Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; 
Canadian drug name; 
Prototype drug