Fosamprenavir in Infants and Children With HIV-1 Infection

Marcia L. Buck, Pharm.D., FCCP, FPPAG

Pediatr Pharm. 2012;18(7)

Abstract and Introduction

Introduction

on April 27, 2012, the Food and Drug Administration (FDA) announced the extension of approval for fosamprenavir to include patients 4 weeks of age and older with HIV-1 infection.^[1] Fosamprenavir was approved by the FDA for use in adults on October 20, 2003 and has become a common part of highly active antiretroviral treatment (HAART) regimens.^[2] Approval was extended to children over 6 years of age in October 2007. With the availability of new clinical research resulting in the extension of approval to infants and young children, fosamprenavir is now an option for more patients with HIV-1 infection.

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Table 1. Contraindicated Fosamprenavir Drug Combinations ^a
Drug or Drug Class	Effect
Alfuzosin	Hypotension
Cisapride	Arrhythmias
Delavirdine	Loss of virologic response
Dihydroergotamine, Ergotamine	Acute ergot toxicity
Flecainide	Inc concentrations leading to arrhythmias if used with ritonavir
Lovastatin	Myopathy
Midazolam	Inc sedation, respiratory depression
Pimozide	Arrhythmias
Propafenone	Inc concentrations leading to arrhythmias if used with ritonavir
Rifampin	Loss of virologic response
Sildenafil (for PAH)	Inc concentrations of sildenafil leading to toxicity
Simvastatin	Myopathy
St. John's wort	Loss of virologic response
Triazolam	Inc sedation, respiratory depression

^aInc, increased; PAH, pulmonary arterial hypertension

Table 2. Potentially Significant Fosamprenavir Drug Interactions ^a
Drug or Class	Effect or Recommendation
Antiarrhythmics (amiodarone, bepridil, dronedarone, lidocaine, quinidine)	Inc concentrations may lead to life-threatening arrhythmias
Anticonvulsants	Carbamazepine, phenobarbital, and phenytoin may reduce amprenavir concentrations. Fosamprenavir may lower phenytoin concentrations.
Azole antifungals	Inc concentrations of ketoconazole or itraconazole
Atorvastatin	May lower amprenavir concentrations
Benzodiazepines	Reduction of benzodiazepine dose may be needed
Bosentan	Reduced bosentan doses may be necessary
Calcium channel blockers	Close monitoring is recommended
Colchicine	Fosamprenavir dose reduction is necessary
Dexamethasone	May lower amprenavir concentrations
Efavirenz	Additional ritonavir is recommended when given with fosamprenavir/ritonavir once daily. No change is needed with twice daily dosing.
Fluticasone	Reduced cortisol concentrations; use not recommended
H₂ blockers	May lower amprenavir concentrations
Immunosuppressants: cyclosporine, tacrolimus, rapamycin	Therapeutic drug monitoring recommended
Macrolide antibiotics (clarithromycin and erythromycin)	Use with caution, may lower amprenavir concentrations
Nevirapine	Not recommended with fosamprenavir alone. No dose change required when dosing fosamprenavir/ritonavir twice daily.
Oral contraceptives	Use not recommended; may lead to loss of virologic response
PDE5 inhibitors: sildenafil, tadalafil, vardenafil used intermittently	Inc PDE5 inhibitor concentrations; reduced doses of these drugs are recommended
Paroxetine	Fosamprenavir/ritonavir may lower paroxetine concentrations
Rifabutin	Reduce rifabutin dose by at least 50% and monitor for neutropenia
Salmeterol	Inc salmeterol concentrations; use not recommended
Trazodone	Inc trazodone concentrations
Tricyclic antidepressants	Therapeutic drug monitoring recommended
Warfarin	Altered warfarin concentrations; close INR monitoring recommended

^aInc, increased

Table 3. Pediatric Fosamprenavir Dosing
Weight	Dose (given twice daily)
< 11 kg	45 mg/kg with ritonavir 7 mg/kg
11–14.9 kg	30 mg/kg with ritonavir 3 mg/kg
15–19.9 kg	23 mg/kg with ritonavir 3 mg/kg
≥ 20 kg	18 mg/kg with ritonavir 3 mg/kg, to a max of 700 mg fosamprenavir and 100 mg ritonavir

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