When administered intravenously fosaprepitant is rapidly converted to aprepitant.
Drug interactions following administration of fosaprepitant are likely to occur with active substances that interact with oral aprepitant. The following information was derived from data with oral aprepitant and studies conducted with fosaprepitant and midazolam or diltiazem.
Aprepitant (125 mg/ 80 mg) is a substrate, a moderate inhibitor, and an inducer of CYP3A4. Aprepitant is also an inducer of CYP2C9. During treatment with oral aprepitant, CYP3A4 is inhibited. After the end of treatment, oral aprepitant causes a transient mild induction of CYP2C9, CYP3A4 and glucuronidation. Fosaprepitant or aprepitant does not seem to interact with the P-glycoprotein transporter, as demonstrated by the lack of interaction of oral aprepitant with digoxin. It is anticipated that fosaprepitant 115 mg as part of the 3-day regimen with aprepitant would cause similar induction of CYP2C9, CYP3A4 and glucuronidation as that caused by the administration of the 3-day regimen of oral aprepitant. Data are lacking regarding effects on CYP2C8 and CYP2C19.
Effect of fosaprepitant / aprepitant on the pharmacokinetics of other active substances
CYP3A4 inhibition
As a moderate inhibitor of CYP3A4, aprepitant can increase plasma concentrations of orally co-administered active substances that are metabolised through CYP3A4. The total exposure of orally administered CYP3A4 substrates may increase up to approximately 3-fold during the 3-day treatment with fosaprepitant followed by oral aprepitant; the effect of aprepitant on the plasma concentrations of intravenously administered CYP3A4 substrates is expected to be smaller. Fosaprepitant must not be used concurrently with pimozide, terfenadine, astemizole, or cisapride. Inhibition of CYP3A4 by aprepitant could result in elevated plasma concentrations of these active substances, potentially causing serious or life-threatening reactions (see section 4.3). Caution is advised during concomitant administration of fosaprepitant and orally administered active substances that are metabolised primarily through CYP3A4 and with a narrow therapeutic range, such as cyclosporine, tacrolimus, sirolimus, everolimus, alfentanil, diergotamine, ergotamine, fentanyl, and quinidine (see section 4.4).
Corticosteroids:
Dexamethasone: The usual oral dexamethasone dose should be reduced by approximately 50 % when co-administered with a regimen of fosaprepitant followed by aprepitant. The dose of dexamethasone in chemotherapy induced nausea and vomiting clinical trials was chosen to account for active substance interactions (see section 4.2). Oral aprepitant, when given as a regimen of 125 mg with dexamethasone co-administered orally as 20 mg on Day 1, and oral aprepitant when given as 80 mg/day with dexamethasone co-administered orally as 8 mg on Days 2 through 5, increased the AUC of dexamethasone, a CYP3A4 substrate, 2.2-fold on Days 1 and 5.
Methylprednisolone: The usual intravenously administered methylprednisolone dose should be reduced approximately 25 %, and the usual oral methylprednisolone dose should be reduced approximately 50 % when co-administered with a regimen of fosaprepitant followed by aprepitant. Oral aprepitant, when given as a regimen of 125 mg on Day 1 and 80 mg/day on Days 2 and 3, increased the AUC of methylprednisolone, a CYP3A4 substrate, by 1.3-fold on Day 1 and by 2.5-fold on Day 3, when methylprednisolone was co-administered intravenously as 125 mg on Day 1 and orally as 40 mg on Days 2 and 3.
During continuous treatment with methylprednisolone, the AUC of methylprednisolone may decrease at later time points within 2 weeks following initiation of dosing with oral aprepitant, due to the inducing effect of aprepitant on CYP3A4. This effect may be expected to be more pronounced for orally administered methylprednisolone.
Chemotherapeutic medicinal products: In pharmacokinetic studies, oral aprepitant, when given as a regimen of 125 mg on Day 1 and 80 mg/day on Days 2 and 3, did not influence the pharmacokinetics of docetaxel administered intravenously on Day 1 or vinorelbine administered intravenously on Day 1 or Day 8. Because the effect of aprepitant on the pharmacokinetics of orally administered CYP3A4 substrates is greater than the effect of aprepitant on the pharmacokinetics of intravenously administered CYP3A4 substrates, an interaction with orally administered chemotherapeutic agents metabolised primarily or in part by CYP3A4 (e.g., etoposide, vinorelbine) cannot be excluded. Caution is advised and additional monitoring may be appropriate in patients receiving such agents (see section 4.4).
Immunosuppressants:
During the 3-day CINV regimen, a transient moderate increase followed by a mild decrease in exposure of immunosuppressants metabolised by CYP3A4 (e.g. cyclosporine, tacrolimus, everolimus and sirolimus) is expected. Given the short duration of the 3-day regimen and the time-dependent limited changes in exposure, dose reduction of the immunosuppressants is not recommended during the 3 days of co-administration with aprepitant.
Midazolam: The potential effects of increased plasma concentrations of midazolam or other benzodiazepines metabolised via CYP3A4 (alprazolam, triazolam) should be considered when co-admin |