Fosamprenavir Calcium

1 INDICATIONS AND USAGE Fosamprenavir calcium tablets are indicated in combination with other antiretroviral agents for the treatment of human immunodeficiency virus (HIV-1) infection. The following points should be considered when initiating therapy with fosamprenavir plus ritonavir in protease inhibitor-experienced patients: • The protease inhibitor-experienced patient trial was not large enough to reach a definitive conclusion that fosamprenavir plus ritonavir and lopinavir plus ritonavir are clinically equivalent [see Clinical Studies (14.2) ] . • Once-daily administration of fosamprenavir plus ritonavir is not recommended for adult protease inhibitor-experienced patients or any pediatric patients [see Dosage and Administration (2.2 , 2.3) , Clinical Studies (14.2 , 14.3) ]. • Dosing of fosamprenavir plus ritonavir is not recommended for protease inhibitor-experienced pediatric patients younger than 6 months [see Clinical Pharmacology (12.3)] . Fosamprenavir calcium tablets are an HIV protease inhibitor indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection. ( 1 )

2 DOSAGE AND ADMINISTRATION • Therapy-Naive Adults: Fosamprenavir 1,400 mg twice daily; fosamprenavir 1,400 mg once daily plus ritonavir 200 mg once daily; fosamprenavir 1,400 mg once daily plus ritonavir 100 mg once daily; fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. ( 2.2 ) • Protease Inhibitor-Experienced Adults: Fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. ( 2.2 ) • Pregnant Patients: Fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily should only be considered in women who are already on a stable twice-daily regimen of fosamprenavir/ritonavir 700 mg/100 mg prior to pregnancy and who are virologically suppressed (HIV-1 RNA less than 50 copies per mL). ( 2.2 ) • Pediatric Patients (aged at least 4 weeks to 18 years): Dosage should be calculated based on body weight (kg) and should not exceed adult dose. ( 2.3 ) • Hepatic Impairment: Recommended adjustments for patients with mild, moderate, or severe hepatic impairment. ( 2.4 ) Dosing Considerations • Fosamprenavir calcium tablets may be taken with or without food. ( 2.1 ) 2.1 General Dosing Information Fosamprenavir calcium tablets may be taken with or without food. Higher-than-approved dose combinations of fosamprenavir plus ritonavir are not recommended due to an increased risk of transaminase elevations [see Overdosage (10) ] . When fosamprenavir is used in combination with ritonavir, prescribers should consult the full prescribing information for ritonavir. 2.2 Adults Therapy-Naive Adults • Fosamprenavir 1,400 mg twice daily (without ritonavir). • Fosamprenavir 1,400 mg once daily plus ritonavir 200 mg once daily. • Fosamprenavir 1,400 mg once daily plus ritonavir 100 mg once daily. o Dosing of fosamprenavir 1,400 mg once daily plus ritonavir 100 mg once daily is supported by pharmacokinetic data [see Clinical Pharmacology (12.3) ] . • Fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. o Dosing of fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily is supported by pharmacokinetic and safety data [see Clinical Pharmacology (12.3) ] . Protease Inhibitor-Experienced Adults • Fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. Pregnancy • Fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. o Dosing of fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily should only be considered in pregnant patients who are already on a stable twice-daily regimen of fosamprenavir/ritonavir 700 mg/100 mg prior to pregnancy and who are virologically suppressed (HIV-1 RNA less than 50 copies per mL). Lower exposures of amprenavir were observed during pregnancy; therefore, viral load should be monitored closely to ensure viral suppression is maintained [see Use in Specific Populations (8.1) , Clinical Pharmacology (12.3) ] . Data regarding use of other regimens of fosamprenavir (with or without ritonavir) in pregnancy are not available. 2.3 Pediatric Patients (Aged at Least 4 Weeks to 18 Years) The recommended dosage of fosamprenavir in patients aged at least 4 weeks to 18 years should be calculated based on body weight (kg) and should not exceed the recommended adult dose (Table 1). Table 1. Twice-Daily Dosage Regimens by Weight for Protease Inhibitor-Naive Pediatric Patients (Aged 4 Weeks and Older) and for Protease Inhibitor-Experienced Pediatric Patients (Aged 6 Months and Older) Using Fosamprenavir Calcium Oral Suspension with Concurrent Ritonavir Weight Twice-Daily Dosage Regimen < 11 kg Fosamprenavir 45 mg/kg plus ritonavir 7 mg/kg When dosing with ritonavir, do not exceed the adult dose of fosamprenavir 700 mg/ritonavir 100 mg twice-daily dose. 11 kg - < 15 kg Fosamprenavir 30 mg/kg plus ritonavir 3 mg/kg 15 kg - < 20 kg Fosamprenavir 23 mg/kg plus ritonavir 3 mg/kg ≥ 20 kg Fosamprenavir 18 mg/kg plus ritonavir 3 mg/kg Alternatively, protease inhibitor-naive children aged 2 years and older can be administered fosamprenavir (without ritonavir) 30 mg per kg twice daily. Fosamprenavir should only be administered to infants born at 38 weeks’ gestation or greater and who have attained a postnatal age of 28 days. For pediatric patients, pharmacokinetic and clinical data: • do not support once-daily dosing of fosamprenavir alone or in combination with ritonavir [see Clinical Studies (14.3) ]. • do not support administration of fosamprenavir alone or in combination with ritonavir for protease inhibitor-experienced children younger than 6 months [see Clinical Pharmacology (12.3)] . • do not support twice-daily dosing of fosamprenavir without ritonavir in pediatric patients younger than 2 years [see Clinical Pharmacology (12.3) ] . Other Dosing Considerations • When administered without ritonavir, the adult regimen of fosamprenavir calcium tablets 1,400 mg twice daily may be used for pediatric patients weighing at least 47 kg. • When administered in combination with ritonavir, fosamprenavir calcium tablets may be used for pediatric patients weighing at least 39 kg; ritonavir capsules may be used for pediatric patients weighing at least 33 kg. 2.4 Patients with Hepatic Impairment See Clinical Pharmacology (12.3) . Mild Hepatic Impairment (Child-Pugh Score Ranging from 5 to 6) Fosamprenavir should be used with caution at a reduced dosage of 700 mg twice daily without ritonavir (therapy-naive) or 700 mg twice daily plus ritonavir 100 mg once daily (therapy-naive or protease inhibitor-experienced). Moderate Hepatic Impairment (Child-Pugh Score Ranging from 7 to 9) Fosamprenavir should be used with caution at a reduced dosage of 700 mg twice daily without ritonavir (therapy-naive), or 450 mg twice daily plus ritonavir 100 mg once daily (therapy-naive or protease inhibitor-experienced). Severe Hepatic Impairment (Child-Pugh Score Ranging from 10 to 15) Fosamprenavir should be used with caution at a reduced dosage of 350 mg twice daily without ritonavir (therapy-naive) or 300 mg twice daily plus ritonavir 100 mg once daily (therapy-naive or protease inhibitor-experienced). There are no data to support dosing recommendations for pediatric patients with hepatic impairment.

6 ADVERSE REACTIONS • Severe or life-threatening skin reactions have been reported with the use of fosamprenavir [see Warnings and Precautions (5.2) ] . • The most common moderate to severe adverse reactions in clinical trials of fosamprenavir were diarrhea, rash, nausea, vomiting, and headache. • Treatment discontinuation due to adverse events occurred in 6.4% of subjects receiving fosamprenavir and in 5.9% of subjects receiving comparator treatments. The most common adverse reactions leading to discontinuation of fosamprenavir (incidence less than or equal to 1% of subjects) included diarrhea, nausea, vomiting, AST increased, ALT increased, and rash. • In adults the most common adverse reactions (incidence greater than or equal to 4%) are diarrhea, rash, nausea, vomiting, and headache. ( 6.1 ) • Vomiting and neutropenia were more frequent in pediatrics than in adults. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Mylan at 1-877-446-3679 (1-877-4-INFO-RX) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Adult Trials The data for the 3 active-controlled clinical trials described below reflect exposure of 700 HIV-1– infected subjects to fosamprenavir calcium tablets, including 599 subjects exposed to fosamprenavir for greater than 24 weeks, and 409 subjects exposed for greater than 48 weeks. The population age ranged from 17 to 72 years. Of these subjects, 26% were female, 51% white, 31% black, 16% American Hispanic, and 70% were antiretroviral-naive. Sixty-one percent received fosamprenavir 1,400 mg once daily plus ritonavir 200 mg once daily; 24% received fosamprenavir 1,400 mg twice daily; and 15% received fosamprenavir 700 mg twice daily plus ritonavir 100 mg twice daily. Selected adverse reactions reported during the clinical efficacy trials of fosamprenavir are shown in Tables 2 and 3. Each table presents adverse reactions of moderate or severe intensity in subjects treated with combination therapy for up to 48 weeks. Table 2. Selected Moderate/Severe Clinical Adverse Reactions Reported in Greater than or Equal to 2% of Antiretroviral-Naive Adult Subjects Adverse Reaction APV30001 All subjects also received abacavir and lamivudine twice daily. APV30002 Fosamprenavir 1,400 mg Twice Daily (n = 166) Nelfinavir 1,250 mg Twice Daily (n = 83) Fosamprenavir 1,400 mg and Ritonavir 200 mg Once Daily (n = 322) Nelfinavir 1,250 mg Twice Daily (n = 327) Gastrointestinal Diarrhea 5% 18% 10% 18% Nausea 7% 4% 7% 5% Vomiting 2% 4% 6% 4% Abdominal pain 1% 0% 2% 2% Skin Rash 8% 2% 3% 2% General disorders Fatigue 2% 1% 4% 2% Nervous system Headache 2% 4% 3% 3% Table 3. Selected Moderate/Severe Clinical Adverse Reactions Reported in Greater than or Equal to 2% of Protease Inhibitor-Experienced Adult Subjects (Trial APV30003) Adverse Reaction Fosamprenavir 700 mg and Ritonavir 100 mg Twice Daily All subjects also received 2 reverse transcriptase inhibitors. (n = 106) Lopinavir 400 mg and Ritonavir 100 mg Twice Daily (n = 103) Gastrointestinal Diarrhea 13% 11% Nausea 3% 9% Vomiting 3% 5% Abdominal pain < 1% 2% Skin Rash 3% 0% Nervous system Headache 4% 2% Skin rash (without regard to causality) occurred in approximately 19% of subjects treated with fosamprenavir in the pivotal efficacy trials. Rashes were usually maculopapular and of mild or moderate intensity, some with pruritus. Rash had a median onset of 11 days after initiation of fosamprenavir and had a median duration of 13 days. Skin rash led to discontinuation of fosamprenavir in less than 1% of subjects. In some subjects with mild or moderate rash, dosing with fosamprenavir was often continued without interruption; if interrupted, reintroduction of fosamprenavir generally did not result in rash recurrence. The percentages of subjects with Grade 3 or 4 laboratory abnormalities in the clinical efficacy trials of fosamprenavir are presented in Tables 4 and 5. Table 4. Grade 3/4 Laboratory Abnormalities Reported in Greater than or Equal to 2% of Antiretroviral-Naive Adult Subjects in Trials APV30001 and APV30002 ULN = Upper limit of normal. Laboratory Abnormality APV30001 All subjects also received abacavir and lamivudine twice daily. APV30002 Fosamprenavir 1,400 mg Twice Daily (n = 166) Nelfinavir 1,250 mg Twice Daily (n = 83) Fosamprenavir 1,400 mg and Ritonavir 200 mg Once Daily (n = 322) Nelfinavir 1,250 mg Twice Daily (n = 327) ALT (> 5 x ULN) 6% 5% 8% 8% AST (> 5 x ULN) 6% 6% 6% 7% Serum lipase (> 2 x ULN) 8% 4% 6% 4% Triglycerides Fasting specimens. (> 750 mg/dL) 0% 1% 6% 2% Neutrophil count, absolute (< 750 cells/mm 3 ) 3% 6% 3% 4% The incidence of Grade 3 or 4 hyperglycemia in antiretroviral-naive subjects who received fosamprenavir in the pivotal trials was less than 1%. Table 5. Grade 3/4 Laboratory Abnormalities Reported in Greater than or Equal to 2% of Protease Inhibitor-Experienced Adult Subjects in Trial APV30003 ULN = Upper limit of normal. Laboratory Abnormality Fosamprenavir 700 mg and Ritonavir 100 mg Twice Daily. All subjects also received 2 reverse transcriptase inhibitors. (n = 104) Lopinavir 400 mg and Ritonavir 100 mg Twice Daily (n = 103) Triglycerides Fasting specimens. (> 750 mg/dL) 11% n = 100 for fosamprenavir plus ritonavir, n = 98 for lopinavir plus ritonavir. 6% Serum lipase (> 2 x ULN) 5% 12% ALT (> 5 x ULN) 4% 4% AST (> 5 x ULN) 4% 2% Glucose (> 251 mg/dL) 2% 2% Pediatric Trials Fosamprenavir with and without ritonavir was studied in 237 HIV-1– infected pediatric subjects aged at least 4 weeks to 18 years in 3 open-label trials; APV20002, APV20003, and APV29005 [see Clinical Studies (14.3) ] . Vomiting and neutropenia occurred more frequently in pediatric subjects compared with adults. Other adverse events occurred with similar frequency in pediatric subjects compared with adults. The frequency of vomiting among pediatric subjects receiving fosamprenavir twice daily with ritonavir was 20% in subjects aged at least 4 weeks to younger than 2 years and 36% in subjects aged 2 to 18 years compared with 10% in adults. The frequency of vomiting among pediatric subjects receiving fosamprenavir twice daily without ritonavir was 60% in subjects aged 2 to 5 years compared with 16% in adults. The median duration of drug-related vomiting episodes in APV29005 was 1 day (range: 1 to 3 days), in APV20003 was 16 days (range: 1 to 38 days), and in APV20002 was 9 days (range: 4 to 13 days). Vomiting was treatment limiting in 4 pediatric subjects across all 3 trials. The incidence of Grade 3 or 4 neutropenia (neutrophils less than 750 cells per mm 3 ) seen in pediatric subjects treated with fosamprenavir with and without ritonavir was higher (15%) than the incidence seen in adult subjects (3%). Grade 3/4 neutropenia occurred in 10% (5 of 51) of subjects aged at least 4 weeks to younger than 2 years and 16% (28 of 170) of subjects aged 2 to 18 years. 6.2 Postmarketing Experience The following adverse reactions have been identified during postapproval use of fosamprenavir. Because these reactions are reported voluntarily from a population of unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These reactions have been chosen for inclusion due to a combination of their seriousness, frequency of reporting, or potential causal connection to fosamprenavir. Cardiac Disorders: Myocardial infarction. Metabolism and Nutrition Disorders: Hypercholesterolemia. Nervous System Disorders: Oral paresthesia. Skin and Subcutaneous Tissue Disorders: Angioedema. Urogenital: Nephrolithiasis.

12.3 Pharmacokinetics The pharmacokinetic properties of amprenavir after administration of fosamprenavir, with or without ritonavir, have been evaluated in both healthy adult volunteers and in HIV-1–infected subjects; no substantial differences in steady-state amprenavir concentrations were observed between the 2 populations. The pharmacokinetic parameters of amprenavir after administration of fosamprenavir (with and without concomitant ritonavir) are shown in Table 7. Table 7. Geometric Mean (95% CI) Steady-State Plasma Amprenavir Pharmacokinetic Parameters in Adults Regimen C max (mcg/mL) T max (hours) Data shown are median (range). AUC 24 (mcg•h/mL) C tau C tau is the concentration at the end of the dose interval. (mcg/mL) Fosamprenavir 1,400 mg Twice Daily (n = 22) HIV-infected adults. 4.82 (4.06-5.72) 1.3 (0.8-4.0) 33.0 AUC24 was calculated from AUC12 summary data x 2. (27.6-39.2) 0.35 (0.27-0.46) Fosamprenavir 1,400 mg Once Daily plus Ritonavir 200 mg Once Daily (n = 22) Healthy adults. 7.24 (6.32-8.28) 2.1 (0.8-5.0) 69.4 (59.7-80.8) 1.45 (1.16-1.81) Fosamprenavir 1,400 mg Once Daily plus Ritonavir 100 mg Once Daily (n = 36) 7.93 (7.25-8.68) 1.5 (0.75-5.0) 66.4 (61.1-72.1) 0.86 (0.74-1.01) Fosamprenavir 700 mg Twice Daily plus Ritonavir 100 mg Twice Daily (n = 24) 6.08 (5.38-6.86) 1.5 (0.75-5.0) 79.2 (69.0-90.6) 2.12 (1.77-2.54) The mean plasma amprenavir concentrations of the dosing regimens over the dosing intervals are displayed in Figure 1. Figure 1. Mean (±SD) Steady-State Plasma Amprenavir Concentrations and Mean EC50 Values Against HIV from Protease Inhibitor-Naive Subjects (in the Absence of Human Serum) Absorption After administration of a single dose of fosamprenavir to HIV-1–infected subjects, the time to peak amprenavir concentration (T max ) occurred between 1.5 and 4 hours (median 2.5 hours). The absolute oral bioavailability of amprenavir after administration of fosamprenavir in humans has not been established. After administration of a single 1,400-mg dose in the fasted state, fosamprenavir calcium oral suspension (50 mg per mL) and fosamprenavir calcium tablets (700 mg) provided similar amprenavir exposures (AUC); however, the C max of amprenavir after administration of the suspension formulation was 14.5% higher compared with the tablet. Amprenavir is both a substrate for and inducer of P-glycoprotein. Effects of Food on Oral Absorption Administration of a single 1,400 mg-dose of fosamprenavir calcium tablets in the fed state (standardized high-fat meal: 967 kcal, 67 grams fat, 33 grams protein, 58 grams carbohydrate) compared with the fasted state was associated with no significant changes in amprenavir C max , T max , or AUC 0-∞ [see Dosage and Administration (2) ] . Distribution In vitro , amprenavir is approximately 90% bound to plasma proteins, primarily to alpha 1 -acid glycoprotein. In vitro , concentration-dependent binding was observed over the concentration range of 1 to 10 mcg per mL, with decreased binding at higher concentrations. The partitioning of amprenavir into erythrocytes is low, but increases as amprenavir concentrations increase, reflecting the higher amount of unbound drug at higher concentrations. Metabolism After oral administration, fosamprenavir is rapidly and almost completely hydrolyzed to amprenavir and inorganic phosphate prior to reaching the systemic circulation. This occurs in the gut epithelium during absorption. Amprenavir is metabolized in the liver by the CYP3A4 enzyme system. The 2 major metabolites result from oxidation of the tetrahydrofuran and aniline moieties. Glucuronide conjugates of oxidized metabolites have been identified as minor metabolites in urine and feces. Elimination Excretion of unchanged amprenavir in urine and feces is minimal. Unchanged amprenavir in urine accounts for approximately 1% of the dose; unchanged amprenavir was not detectable in feces. Approximately 14% and 75% of an administered single dose of 14 C-amprenavir can be accounted for as metabolites in urine and feces, respectively. Two metabolites accounted for greater than 90% of the radiocarbon in fecal samples. The plasma elimination half-life of amprenavir is approximately 7.7 hours. Specific Populations Patients with Hepatic Impairment The pharmacokinetics of amprenavir have been studied after the administration of fosamprenavir in combination with ritonavir to adult HIV-1–infected subjects with mild, moderate, and severe hepatic impairment. Following 2 weeks of dosing with fosamprenavir plus ritonavir, the AUC of amprenavir was increased by approximately 22% in subjects with mild hepatic impairment, by approximately 70% in subjects with moderate hepatic impairment, and by approximately 80% in subjects with severe hepatic impairment compared with HIV-1–infected subjects with normal hepatic function. Protein binding of amprenavir was decreased in subjects with hepatic impairment. The unbound fraction at 2 hours (approximate C max ) ranged between a decrease of -7% to an increase of 57% while the unbound fraction at the end of the dosing interval (C min ) increased from 50% to 102% [see Dosage and Administration (2.4) ] . The pharmacokinetics of amprenavir have been studied after administration of amprenavir given as AGENERASE ® capsules to adult subjects with hepatic impairment. Following administration of a single 600-mg oral dose, the AUC of amprenavir was increased by approximately 2.5-fold in subjects with moderate cirrhosis and by approximately 4.5-fold in subjects with severe cirrhosis compared with healthy volunteers [see Dosage and Administration (2.4) ] . Patients with Renal Impairment The impact of renal impairment on amprenavir elimination in adults has not been studied. The renal elimination of unchanged amprenavir represents approximately 1% of the administered dose; therefore, renal impairment is not expected to significantly impact the elimination of amprenavir. Pregnant Women Amprenavir pharmacokinetics were studied in pregnant women receiving fosamprenavir (700 mg) plus ritonavir (100 mg) twice daily during the second trimester (n = 6) or third trimester (n = 9) and postpartum (n = 9). Compared to postpartum, geometric mean amprenavir AUC was 35% lower in the second trimester and 25% lower in the third trimester (Table 8). This decrease results in amprenavir concentrations that are within the range observed across regimens of fosamprenavir in non-pregnant adults and lower concentrations compared with fosamprenavir (700 mg) plus ritonavir (100 mg) twice daily in non-pregnant adults (Table 7, Table 8). This decrease is not expected to be considered clinically relevant in patients who are virologically suppressed; however, viral load should be monitored closely to ensure viral suppression is maintained [see Dosage and Administration (2.2) , Use in Specific Populations (8.1) ] . The amprenavir geometric mean ratio (95% CI) of fetal cord to maternal peripheral plasma concentration (n = 7) was 0.27 (0.24 to 0.30). Table 8. Geometric Mean (95% CI) Steady-State Plasma Amprenavir Pharmacokinetic Parameters in Pregnant Women Receiving Fosamprenavir with Ritonavir Pharmacokinetic Parameter Fosamprenavir 700 mg Twice Daily plus Ritonavir 100 mg Twice Daily Second Trimester (n = 6) Third Trimester (n = 9) Postpartum (n = 9) AUC 12 (mcg•h/mL) 26.0 (19.5, 34.6) 30.1 (21.6, 41.9) 39.9 (31.9, 50.1) AUC 24 (mcg•h/mL) AUC24 was calculated from AUC12 summary data x 2. 52.0 (39.0, 69.2) 60.2 (43.2, 83.8) 79.8 (63.8, 100.2) C max (mcg/mL) 4.19 (3.19, 5.51) 5.36 (3.98, 7.22) 6.65 (5.24, 8.44) C tau (mcg/mL) C tau represents the concentration at the end of the dose interval. 1.31 (0.97, 1.77) 1.34 (0.95, 1.89) 2.03 (1.46, 2.83) Pediatric Patients The pharmacokinetics of amprenavir following administration of fosamprenavir calcium oral suspension and fosamprenavir calcium tablets, with or without ritonavir, have been studied in a total of 212 HIV-1–infected pediatric subjects enrolled in 3 trials. Fosamprenavir without ritonavir was administered as 30 or 40 mg per kg twice daily to children aged 2 to 5 years. Fosamprenavir with ritonavir was administered as fosamprenavir 30 mg per kg plus ritonavir 6 mg per kg once daily to children aged 2 to 18 years and as fosamprenavir 18 to 60 mg per kg plus ritonavir 3 to 10 mg per kg twice daily to children aged at least 4 weeks to 18 years; body weights ranged from 3 to 103 kg. Amprenavir apparent clearance decreased with increasing weight. Weight-adjusted apparent clearance was higher in children younger than 4 years, suggesting that younger children require higher mg-per-kg dosing of fosamprenavir. The pharmacokinetics of fosamprenavir calcium oral suspension in protease inhibitor-naive infants younger than 6 months (n = 9) receiving fosamprenavir 45 mg per kg plus ritonavir 10 mg per kg twice daily generally demonstrated lower AUC 12 and C min than adults receiving twice-daily fosamprenavir 700 mg plus ritonavir 100 mg, the dose recommended for protease-experienced adults. The mean steady-state amprenavir AUC 12 , C max , and C min were 26.6 mcg•hour per mL, 6.25 mcg per mL, and 0.86 mcg per mL, respectively. Because of expected low amprenavir exposure and a requirement for large volume of drug, twice-daily dosing of fosamprenavir alone (without ritonavir) in pediatric subjects younger than 2 years was not studied. Pharmacokinetic parameters for fosamprenavir administered with food and with ritonavir in this patient population at the recommended weight-band-based dosage regimens are provided in Table 9. Table 9. Geometric Mean (95% CI) Steady-State Plasma Amprenavir Pharmacokinetic Parameters by Weight in Pediatric and Adolescent Subjects Aged at Least 4 Weeks to 18 Years Receiving Fosamprenavir with Ritonavir Weight Recommended Dosage Regimen C max AUC 24 C min n (mcg/mL) n (mcg•h/mL) n (mcg/mL) < 11 kg Fosamprenavir 45 mg/kg plus Ritonavir 7 mg/kg twice daily 12 6.00 (3.88, 9.29) 12 57.3 (34.1, 96.2) 27 1.65 (1.22, 2.24) 11 kg - < 15 kg Fosamprenavir 30 mg/kg plus Ritonavir 3 mg/kg twice daily Not studied Recommended dose for pediatric patients weighing 11 kg to less than 15 kg is based on population pharmacokinetic analysis. 15 kg - < 20 kg Fosamprenavir 23 mg/kg plus Ritonavir 3 mg/kg twice daily 5 9.54 (4.63, 19.7) 5 121 (54.2, 269) 9 3.56 (2.33, 5.43) 20 kg - < 39 kg Fosamprenavir 18 mg/kg plus Ritonavir 3 mg/kg twice daily 13 6.24 (5.01, 7.77) 12 97.9 (77.0, 124) 23 2.54 (2.11, 3.06) ≥ 39 kg Fosamprenavir 700 mg plus Ritonavir 100 mg twice daily 15 5.03 (4.04, 6.26) 15 72.3 (59.6, 87.6) 42 1.98 (1.72, 2.29) Subjects aged 2 to younger than 6 years receiving fosamprenavir 30 mg per kg twice daily without ritonavir achieved geometric mean (95% CI) amprenavir C max (n = 9), AUC 12 (n = 9), and C min (n = 19) of 7.15 (5.05, 10.1), 22.3 (15.3, 32.6), and 0.513 (0.384, 0.686), respectively. Geriatric Patients The pharmacokinetics of amprenavir after administration of fosamprenavir to patients older than 65 years have not been studied [see Use in Specific Populations (8.5) ] . Male and Female Patients The pharmacokinetics of amprenavir after administration of fosamprenavir do not differ between males and females. Racial Groups The pharmacokinetics of amprenavir after administration of fosamprenavir do not differ between blacks and non-blacks. Drug Interaction Studies [See Contraindications (4) , Warnings and Precautions (5.1) , Drug Interactions (7) .] Amprenavir, the active metabolite of fosamprenavir, is metabolized in the liver by the cytochrome P450 enzyme system. Amprenavir inhibits CYP3A4. Data also suggest that amprenavir induces CYP3A4. Caution should be used when coadministering medications that are substrates, inhibitors, or inducers of CYP3A4, or potentially toxic medications that are metabolized by CYP3A4. Amprenavir does not inhibit CYP2D6, CYP1A2, CYP2C9, CYP2C19, CYP2E1, or uridine glucuronosyltransferase (UDPGT). Amprenavir is both a substrate for and inducer of P-glycoprotein. Drug interaction trials were performed with fosamprenavir and other drugs likely to be coadministered or drugs commonly used as probes for pharmacokinetic interactions. The effects of coadministration on AUC, C max , and C min values are summarized in Table 10 (effect of other drugs on amprenavir) and Table 12 (effect of fosamprenavir on other drugs). In addition, since fosamprenavir delivers comparable amprenavir plasma concentrations as AGENERASE, drug interaction data derived from trials with AGENERASE are provided in Tables 11 and 13. For information regarding clinical recommendations, [see Drug Interactions (7) ] . Table 10. Drug Interactions: Pharmacokinetic Parameters for Amprenavir after Administration of Fosamprenavir in the Presence of the Coadministered Drug(s) ↑ = Increase; ↓ = Decrease; ↔ = No change (↑ or ↓ less than or equal to 10%), NA = Not applicable. Coadministered Drug(s) and Dose(s) Dose of Fosamprenavir Concomitant medication is also shown in this column where appropriate. n % Change in Amprenavir Pharmacokinetic Parameters (90% CI) C max AUC C min Antacid (MAALOX TC) 30-mL single dose 1,400-mg single dose 30 ↓35 (↓24 to ↓42) ↓18 (↓9 to ↓26) ↑14 (↓7 to ↑39) Atazanavir 300 mg once daily for 10 days 700 mg twice daily plus ritonavir 100 mg twice daily for 10 days 22 ↔ ↔ ↔ Atorvastatin 10 mg once daily for 4 days 1,400 mg twice daily for 2 weeks 16 ↓18 (↓34 to ↑1) ↓27 (↓41 to ↓12) ↓12 (↓27 to ↓6) Atorvastatin 10 mg once daily for 4 days 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 16 ↔ ↔ ↔ Efavirenz 600 mg once daily for 2 weeks 1,400 mg once daily plus ritonavir 200 mg once daily for 2 weeks 16 ↔ ↓13 (↓30 to ↑7) ↓36 (↓8 to ↓56) Efavirenz 600 mg once daily plus additional ritonavir 100 mg once daily for 2 weeks 1,400 mg once daily plus ritonavir 200 mg once daily for 2 weeks 16 ↑18 (↑1 to ↑38) ↑11 (0 to ↑24) ↔ Efavirenz 600 mg once daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 16 ↔ ↔ ↓17 (↓4 to ↓29) Esomeprazole 20 mg once daily for 2 weeks 1,400 mg twice daily for 2 weeks 25 ↔ ↔ ↔ Esomeprazole 20 mg once daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 23 ↔ ↔ ↔ Ethinyl estradiol/ norethindrone 0.035 mg/0.5 mg once daily for 21 days 700 mg twice daily plus ritonavir Ritonavir C max , AUC, and C min increased by 63%, 45%, and 13%, respectively, compared with historical control. 100 mg twice daily for 21 days 25 ↔ Compared with historical control. ↔ ↔ Ketoconazole Subjects were receiving fosamprenavir/ritonavir for 10 days prior to the 4-day treatment period with both ketoconazole and fosamprenavir/ritonavir. 200 mg once daily for 4 days 700 mg twice daily plus ritonavir 100 mg twice daily for 4 days 15 ↔ ↔ ↔ Lopinavir/ritonavir 533 mg/133 mg twice daily 1,400 mg twice daily for 2 weeks 18 ↓13 Compared with fosamprenavir 700 mg/ritonavir 100 mg twice daily for 2 weeks. ↓26 ↓42 Lopinavir/ritonavir 400 mg/100 mg twice daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 18 ↓58 (↓42 to ↓70) ↓63 (↓51 to ↓72) ↓65 (↓54 to ↓73) Maraviroc 300 mg twice daily for 10 days 700 mg twice daily plus ritonavir 100 mg twice daily for 20 days 14 ↓34 (↓25 to ↓41) ↓35 (↓29 to ↓41) ↓36 (↓27 to ↓43) Maraviroc 300 mg once daily for 10 days 1,400 mg once daily plus ritonavir 100 mg once daily for 20 days 14 ↓29 (↓20 to ↓38) ↓30 (↓23 to ↓36) ↓15 (↓3 to ↓25) Methadone 70 to 120 mg once daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 19 ↔ ↔ ↔ Nevirapine 200 mg twice daily for 2 weeks Subjects were receiving nevirapine for at least 12 weeks prior to trial. 1,400 mg twice daily for 2 weeks 17 ↓25 (↓37 to ↓10) ↓33 (↓45 to ↓20) ↓35 (↓50 to ↓15) Nevirapine 200 mg twice daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 17 ↔ ↓11 (↓23 to ↑3) ↓19 (↓32 to ↓4) Phenytoin 300 mg once daily for 10 days 700 mg twice daily plus ritonavir 100 mg twice daily for 10 days 13 ↔ ↑20 (↑8 to ↑34) ↑19 (↑6 to ↑33) Raltegravir 400 mg twice daily for 14 days 1,400 mg twice daily for 14 days (fasted) 14 ↓27 (↓46 to ↔) ↓36 (↓53 to ↓13) ↓43 C last (C 12 h or C 24 h ). (↓59 to ↓21) 1,400 mg twice daily for 14 days Doses of fosamprenavir and raltegravir were given with food on pharmacokinetic sampling days and without regard to food all other days. 14 ↓15 (↓27 to ↓1) ↓17 (↓27 to ↓6) ↓32 (↓53 to ↓1) 700 mg twice daily plus ritonavir 100 mg twice daily for 14 days (fasted) 14 ↓14 (↓39 to ↑20) ↓17 (↓38 to ↑12) ↓20 (↓45 to ↑17) 700 mg twice daily plus ritonavir 100 mg twice daily for 14 days 12 ↓25 (↓42 to ↓2) ↓25 (↓44 to ↔) ↓33 (↓52 to ↓7) Raltegravir 400 mg twice daily for 14 days 1,400 mg once daily plus ritonavir 100 mg once daily for 14 days (fasted) 13 ↓18 (↓34 to ↔) ↓24 (↓41 to ↔) ↓50 (↓64 to ↓31) 1,400 mg once daily plus ritonavir 100 mg once daily for 14 days 14 ↑27 (↓1 to ↑62) ↑13 (↓7 to ↑38) ↓17 (↓45 to ↑26) Ranitidine 300-mg single dose (administered 1 hour before fosamprenavir) 1,400-mg single dose 30 ↓51 (↓43 to ↓58) ↓30 (↓22 to ↓37) ↔ (↓19 to ↑21) Rifabutin 150 mg every other day for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 15 ↑36 (↑18 to ↑55) ↑35 (↑17 to ↑56) ↑17 (↓1 to ↑39) Tenofovir 300 mg once daily for 4 to 48 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 4 to 48 weeks 45 NA NA ↔ Compared with parallel control group. Tenofovir 300 mg once daily for 4 to 48 weeks 1,400 mg once daily plus ritonavir 200 mg once daily for 4 to 48 weeks 60 NA NA ↔ Table 11. Drug Interactions: Pharmacokinetic Parameters for Amprenavir after Administration of AGENERASE in the Presence of the Coadministered Drug(s) ↑ = Increase; ↓ = Decrease; ↔ = No change (↑ or ↓ less than 10%); NA = C min not calculated for single-dose trial. Coadministered Drug(s) and Dose(s) Dose of AGENERASE Compared with parallel control group. n % Change in Amprenavir Pharmacokinetic Parameters (90% CI) C max AUC C min Abacavir 300 mg twice daily for 2 to 3 weeks 900 mg twice daily for 2 to 3 weeks 4 ↔ ↔ ↔ Clarithromycin 500 mg twice daily for 4 days 1,200 mg twice daily for 4 days 12 ↑15 (↑1 to ↑31) ↑18 (↑8 to ↑29) ↑39 (↑31 to ↑47) Delavirdine 600 mg twice daily for 10 days 600 mg twice daily for 10 days 9 ↑40 Median percent change; confidence interval not reported. ↑130 ↑125 Ethinyl estradiol/ norethindrone 0.035 mg/1 mg for 1 cycle 1,200 mg twice daily for 28 days 10 ↔ ↓22 (↓35 to ↓8) ↓20 (↓41 to ↑8) Indinavir 800 mg 3 times a day for 2 weeks (fasted) 750 or 800 mg 3 times a day for 2 weeks (fasted) 9 ↑18 (↑13 to ↑58) ↑33 (↑2 to ↑73) ↑25 (↓27 to ↑116) Ketoconazole 400-mg single dose 1,200-mg single dose 12 ↓16 (↓25 to ↓6) ↑31 (↑20 to ↑42) NA Lamivudine 150-mg single dose 600-mg single dose 11 ↔ ↔ NA Methadone 44 to 100 mg once daily for > 30 days 1,200 mg twice daily for 10 days 16 ↓27 Compared with historical data. ↓30 ↓25 Nelfinavir 750 mg 3 times a day for 2 weeks (fed) 750 or 800 mg 3 times a day for 2 weeks (fed) 6 ↓14 (↓38 to ↑20) ↔ ↑189 (↑52 to ↑448) Rifabutin 300 mg once daily for 10 days 1,200 mg twice daily for 10 days 5 ↔ ↓15 (↓28 to 0) ↓15 (↓38 to ↑17) Rifampin 300 mg once daily for 4 days 1,200 mg twice daily for 4 days 11 ↓70 (↓76 to ↓62) ↓82 (↓84 to ↓78) ↓92 (↓95 to ↓89) Saquinavir 800 mg 3 times a day for 2 weeks (fed) 750 or 800 mg 3 times a day for 2 weeks (fed) 7 ↓37 (↓54 to ↓14) ↓32 (↓49 to ↓9) ↓14 (↓52 to ↑54) Zidovudine 300-mg single dose 600-mg single dose 12 ↔ ↑13 (↓2 to ↑31) NA Table 12. Drug Interactions: Pharmacokinetic Parameters for Coadministered Drug in the Presence of Amprenavir after Administration of Fosamprenavir ↑ = Increase; ↓ = Decrease; ↔ = No change (↑ or ↓less than 10%); ND = Interaction cannot be determined as C min was below the lower limit of quantitation. Coadministered Drug(s) and Dose(s) Dose of Fosamprenavir Concomitant medication is also shown in this column where appropriate. n % Change in Pharmacokinetic Parameters of Coadministered Drug (90% CI) C max AUC C min Atazanavir 300 mg once daily for 10 days Comparison arm of atazanavir 300 mg once daily plus ritonavir 100 mg once daily for 10 days. 700 mg twice daily plus ritonavir 100 mg twice daily for 10 days 21 ↓24 (↓39 to ↓6) ↓22 (↓34 to ↓9) ↔ Atorvastatin 10 mg once daily for 4 days 1,400 mg twice daily for 2 weeks 16 ↑304 (↑205 to ↑437) ↑130 (↑100 to ↑164) ↓10 (↓27 to ↑12) Atorvastatin 10 mg once daily for 4 days 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 16 ↑184 (↑126 to ↑257) ↑153 (↑115 to ↑199) ↑73 (↑45 to ↑108) Esomeprazole 20 mg once daily for 2 weeks 1,400 mg twice daily for 2 weeks 25 ↔ ↑55 (↑39 to ↑73) ND Esomeprazole 20 mg once daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 23 ↔ ↔ ND Ethinyl estradiol Administered as a combination oral contraceptive tablet: ethinyl estradiol 0.035 mg/norethindrone 0.5 mg. 0.035 mg once daily for 21 days 700 mg twice daily plus ritonavir 100 mg twice daily for 21 days 25 ↓28 (↓21 to ↓35) ↓37 (↓30 to ↓42) ND Dolutegravir 50 mg once daily 700 mg twice daily plus ritonavir 100 mg twice daily 12 ↓24 (↓8 to ↓37) ↓35 (↓22 to ↓46) ↓49 (↓37 to ↓59) Ketoconazole Subjects were receiving fosamprenavir/ritonavir for 10 days prior to the 4-day treatment period with both ketoconazole and fosamprenavir/ritonavir. 200 mg once daily for 4 days 700 mg twice daily plus ritonavir 100 mg twice daily for 4 days 15 ↑25 (↑0 to ↑56) ↑169 (↑108 to ↑248) ND Lopinavir/ritonavir Data represent lopinavir concentrations. 533 mg/133 mg twice daily for 2 weeks 1,400 mg twice daily for 2 weeks 18 ↔ Compared with lopinavir 400 mg/ritonavir 100 mg twice daily for 2 weeks. ↔ ↔ Lopinavir/ritonavir 400 mg/100 mg twice daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 18 ↑30 (↓15 to ↑47) ↑37 (↓20 to ↑55) ↑52 (↓28 to ↑82) Maraviroc 300 mg twice daily for 10 days 700 mg twice daily plus ritonavir 100 mg twice daily for 20 days 14 ↑52 (↑27 to ↑82) ↑149 (↑119 to ↑182) ↑374 (↑303 to ↑457) Maraviroc 300 mg once daily for 10 days 1,400 mg once daily plus ritonavir 100 mg once daily for 20 days 14 ↑45 (↑20 to ↑74) ↑126 (↑99 to ↑158) ↑80 (↑53 to ↑113) Methadone 70 to 120 mg once daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 19 R-Methadone (active) ↓21 Dose normalized to methadone 100 mg. The unbound concentration of the active moiety, R-methadone, was unchanged. (↓30 to ↓12) ↓18 (↓27 to ↓8) ↓11 (↓21 to ↑1) S-Methadone (inactive) ↓43 (↓49 to ↓37) ↓43 (↓50 to ↓36) ↓41 (↓49 to ↓31) Nevirapine 200 mg twice daily for 2 weeks Subjects were receiving nevirapine for at least 12 weeks prior to trial. 1,400 mg twice daily for 2 weeks 17 ↑25 (↑14 to ↑37) ↑29 (↑19 to ↑40) ↑34 (↑20 to ↑49) Nevirapine 200 mg twice daily for 2 weeks 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 17 ↑13 (↑3 to ↑24) ↑14 (↑5 to ↑24) ↑22 (↑9 to ↑35) Norethindrone 0.5 mg once daily for 21 days 700 mg twice daily plus ritonavir 100 mg twice daily for 21 days 25 ↓38 (↓32 to ↓44) ↓34 (↓30 to ↓37) ↓26 (↓20 to ↓32) Phenytoin 300 mg once daily for 10 days 700 mg twice daily plus ritonavir 100 mg twice daily for 10 days 14 ↓20 (↓12 to ↓27) ↓22 (↓17 to ↓27) ↓29 (↓23 to ↓34) Rifabutin 150 mg every other day for 2 weeks Comparison arm of rifabutin 300 mg once daily for 2 weeks. AUC is AUC (0-48 h) . 700 mg twice daily plus ritonavir 100 mg twice daily for 2 weeks 15 ↓14 (↓28 to ↑4) ↔ ↑28 (↑12 to ↑46) (25-O-desacetylrifabutin metabolite) ↑579 (↑479 to ↑698) ↑1,120 (↑965 to ↑1,300) ↑2,510 (↑1,910 to ↑3,300) Rifabutin + 25-O-desacetylrifabutin metabolite NA ↑64 (↑46 to ↑84) NA Rosuvastatin 10-mg single dose 700 mg twice daily plus ritonavir 100 mg twice daily for 7 days ↑45 ↑8 NA Table 13. Drug Interactions: Pharmacokinetic Parameters for Coadministered Drug in the Presence of Amprenavir after Administration of AGENERASE ↑ = Increase; ↓ = Decrease; ↔ = No change (↑ or ↓ less than 10%); NA = C min not calculated for single-dose trial; ND = Interaction cannot be determined as C min was below the lower limit of quantitation. Coadministered Drug(s) and Dose(s) Dose of AGENERASE n % Change in Pharmacokinetic Parameters of Coadministered Drug (90% CI) C max AUC C min Abacavir 300 mg twice daily for 2 to 3 weeks 900 mg twice daily for 2 to 3 weeks 4 ↔ Compared with historical data. ↔ ↔ Clarithromycin 500 mg twice daily for 4 days 1,200 mg twice daily for 4 days 12 ↓10 (↓24 to ↑7) ↔ ↔ Delavirdine 600 mg twice daily for 10 days 600 mg twice daily for 10 days 9 ↓47 Median percent change; confidence interval not reported. ↓61 ↓88 Ethinyl estradiol 0.035 mg for 1 cycle 1,200 mg twice daily for 28 days 10 ↔ ↔ ↑32 (↓3 to ↑79) Indinavir 800 mg 3 times a day for 2 weeks (fasted) 750 mg or 800 mg 3 times a day for 2 weeks (fasted) 9 ↓22 ↓38 ↓27 Ketoconazole 400-mg single dose 1,200-mg single dose 12 ↑19 (↑8 to ↑33) ↑44 (↑31 to ↑59) NA Lamivudine 150-mg single dose 600-mg single dose 11 ↔ ↔ NA Methadone 44 mg to 100 mg once daily for > 30 days 1,200 mg twice daily for 10 days 16 R-Methadone (active) ↓25 (↓32 to ↓18) ↓13 (↓21 to ↓5) ↓21 (↓32 to ↓9) S-Methadone (inactive) ↓48 (↓55 to ↓40) ↓40 (↓46 to ↓32) ↓53 (↓60 to ↓43) Nelfinavir 750 mg 3 times a day for 2 weeks (fed) 750 mg or 800 mg 3 times a day for 2 weeks (fed) 6 ↑12 ↑15 ↑14 Norethindrone 1 mg for 1 cycle 1,200 mg twice daily for 28 days 10 ↔ ↑18 (↑1 to ↑38) ↑45 (↑13 to ↑88) Rifabutin 300 mg once daily for 10 days 1,200 mg twice daily for 10 days 5 ↑119 (↑82 to ↑164) ↑193 (↑156 to ↑235) ↑271 (↑171 to ↑409) Rifampin 300 mg once daily for 4 days 1,200 mg twice daily for 4 days 11 ↔ ↔ ND Saquinavir 800 mg 3 times a day for 2 weeks (fed) 750 mg or 800 mg 3 times a day for 2 weeks (fed) 7 ↑21 ↓19 ↓48 Zidovudine 300-mg single dose 600-mg single dose 12 ↑40 (↑14 to ↑71) ↑31 (↑19 to ↑45) NA Figure 1. Mean (±SD) Steady-State Plasma Amprenavir Concentrations and Mean EC50 Values Against HIV from Protease Inhibitor-Naive Subjects (in the Absence of Human Serum)