Aprepitant after Fosaprepitant Administration
Following administration of a single intravenous 150-mg dose of fosaprepitant, a prodrug of aprepitant administered as a 20-minute infusion to healthy subjects, the mean AUC
0-∞of aprepitant was 37.4 (±14.8) mcg•hr/mL and the mean maximal aprepitant concentration (C
max) was 4.2 (±1.2) mcg/mL. Plasma concentrations of fosaprepitant are below the limits of quantification (10 ng/mL) within 30 minutes of the completion of infusion.
Distribution
Aprepitant is greater than 95% bound to plasma proteins. The mean apparent volume of distribution at steady state (Vd
ss) was approximately 70 L in humans.
Aprepitant crosses the blood brain barrier in humans
[see
Clinical Pharmacology (12.1)].
Elimination
Metabolism
Fosaprepitant is converted to aprepitant in
in vitroincubations with human liver preparations and in S9 preparations from multiple other human tissues including kidney, lung and ileum. Thus, it appears that the conversion of fosaprepitant to aprepitant can occur in multiple extrahepatic tissues in addition to the liver.
Aprepitant undergoes extensive metabolism.
In vitrostudies using human liver microsomes indicate that aprepitant is metabolized primarily by CYP3A4 with minor metabolism by CYP1A2 and CYP2C19. Metabolism is largely via oxidation at the morpholine ring and its side chains. No metabolism by CYP2D6, CYP2C9, or CYP2E1 was detected.
In healthy young adults, aprepitant accounts for approximately 24% of the radioactivity in plasma over 72 hours following a single oral 300-mg dose of [
14C]-aprepitant, indicating a substantial presence of metabolites in the plasma. Seven metabolites of aprepitant, which are only weakly active, have been identified in human plasma.
Excretion
Following administration of a single intravenous 100-mg dose of [
14C]-fosaprepitant to healthy subjects, 57% of the radioactivity was recovered in urine and 45% in feces.
Aprepitant is eliminated primarily by metabolism; aprepitant is not renally excreted. The apparent terminal half-life ranged from approximately 9 to 13 hours.
Specific Populations
Age: Geriatric Population
Following oral administration of a single 125-mg dose of aprepitant on Day 1 and 80 mg once daily on Days 2 through 5, the AUC
0-24hrof aprepitant was 21% higher on Day 1 and 36% higher on Day 5 in elderly (65 years and older) relative to younger adults. The C
maxwas 10% higher on Day 1 and 24% higher on Day 5 in elderly relative to younger adults. These differences are not considered clinically meaningful
[see
Use in Specific Populations (8.5)].
Age: Pediatric Population
Single Dose Fosaprepitant for Injection Regimen: Simulated systemic exposures of aprepitant in patients 2 years to less than 12 years and observed systemic exposures in patients 6 months to less than 2 years and 12 to 17 years are shown in Table 9, including AUC
0-24hr, peak plasma concentration (C
max) on Day 1 and concentrations at the end of Day 1 (C
24), Day 2 (C
48) and Day 3 (C
72).
Table 9
Systemic Exposures of Aprepitant for Single Dose Fosaprepitant for Injection Regimen in Pediatric Patients
Population
| Single Dose of Fosaprepitant
for Injection Regimen
| Geometric Mean
|
AUC
0-24hr.
(mcg*hr/mL)
|
C
max (mcg/mL)
|
C
24 (mcg/mL)
|
C
48 (mcg/mL)
|
C
72 (mcg/mL)
|
12 Years to 17 Years
| 150 mg
| 29.4
| 3.4
| 0.7
| ND*
| ND*
|
6 Years to less than 12 Years
|
4 mg/kg
| 35.2
| 3.6
| 0.7
| 0.2
| 0.05
|
2 Years to less than
6 Years
| 28.2
| 3.1
| 0.4
| 0.1
| 0.02
|
6 Months to less than 2 Years
| 5 mg/kg
| 32.7
| 3.3
| 0.4
|
NE
†
|
ND
*
|
*ND = Not Determined. Pharmacokinetic samples were not collected to support the parameter value of interest.
†NE = Not Estimated. The geometric mean could not be estimated due to values being below the limitation of quantification.
3-Day IV/Oral/Oral fosaprepitant Regimen:Simulated aprepitant systemic exposures in patients 6 months to less than 12 years and observed systemic exposures in patients 12 to 17 years are shown in Table 10, including AUC
0-24hr, peak plasma concentration (C
max) on Day 1 and concentrations at the end of Day 1 (C
24), Day 2 (C
48) and Day 3 (C
72).
Table 10
Systemic Exposures of Aprepitant for 3-Day IV/Oral/Oral Regimen in Pediatric Patients
Population
| 3-Day Dose
of
Fosaprepitant
(IV/Oral/Oral*)
| Geometric Mean
|
AUC
0-24hr.
(mcg*hr/mL)
| C
max (mcg/mL)
| C
24 (mcg/mL)
| C
48 (mcg/mL)
| C
72 (mcg/mL)
|
12 Years to 17 Years
| 115/80/80 mg
| 18.0
| 3.0
| 0.4
| 0.2
| NE
†
|
6 Years to less than
12 Years
|
3/2/2 mg/kg
| 25.7
| 2.7
| 0.5
| 0.3
| 0.3
|
2 Years to less than
6 Years
| 20.2
| 2.3
| 0.3
| 0.2
| 0.2
|
6 Months to less than
2 Years
| 16.6
| 1.9
| 0.2
| 0.1
| 0.1
|
*IV on Day 1, Oral on Day 2, and Oral on Day 3
†NE = Not Estimated. The geometric mean could not be estimated due to values being below the limitation of quantification.
3-Day IV/IV/IV fosaprepitant Regimen: Simulated aprepitant systemic exposures in patients 6 months to 17 years are shown in Table 11, including AUC
0-24hr, peak plasma concentration (C
max) on Day 1 and concentrations at the end of Day 1 (C
24), Day 2 (C
48) and Day 3 (C
72).
Table 11
Systemic Exposures of Aprepitant for 3-Day IV/IV/IV Regimen in Pediatric Patients
Population
| 3-Day Dose of Fosaprepitant (IV/IV/IV)*
| Geometric Mean
|
AUC
0-24hr. (mcg*hr/mL)
| C
max (mcg/mL)
| C
24 (mcg/mL)
| C
48 (mcg/mL)
| C
72 (mcg/mL)
|
12 Years to 17 Years
|
115/80/80 mg
| 21.1
| 2.5
| 0.4
| 0.4
| 0.4
|
6 Years to less than 12 Years
|
3/2/2 mg/kg
| 25.6
| 2.7
| 0.5
| 0.4
| 0.4
|
2 Years to less than 6 Years
| 20.3
| 2.3
| 0.3
| 0.2
| 0.2
|
6 Months to less than 2 Years
| 16.7
| 1.9
| 0.2
| 0.2
| 0.2
|
*IV on Day 1, Day 2, and Day 3
Plasma concentrations of fosaprepitant are negligible within 15 to 30 minutes after the completion of the infusion in pediatric patients.