How long does oral Aprepitant (Aprepirant) take to work, and can it be taken with Maxaran, Zofran (ondansetron), Gravol (dimenhydrinate), and Haldol (haloperidol)?

Aprepitant Timing and Compatibility with Other Antiemetics

Oral aprepitant begins working within 3 hours of administration, and can be safely taken with Maxeran (metoclopramide), Zofran (ondansetron), Gravol (dimenhydrinate), and Haldol (haloperidol) as part of a multimodal antiemetic approach. 1

Onset of Action and Pharmacokinetics

• Oral aprepitant reaches peak plasma concentration (Cmax) at approximately 3-4 hours after administration, which correlates with its onset of action 1, 2
• The absolute bioavailability of oral aprepitant is approximately 60-65%, and it can be taken with or without food 2
• Aprepitant crosses the blood-brain barrier and occupies NK1 receptors in the central nervous system, providing a different and complementary mechanism of action compared to other antiemetics 1, 3

Compatibility with Other Antiemetics

• Aprepitant can be safely combined with 5-HT3 receptor antagonists like Zofran (ondansetron) and has been shown to augment their antiemetic activity 3
• Clinical studies have demonstrated that aprepitant regimens including ondansetron are more effective than ondansetron alone for preventing both acute and delayed emesis 3
• Aprepitant can be used alongside haloperidol (Haldol) as part of a multimodal approach for breakthrough emesis treatment 3
• Metoclopramide (Maxeran) and dimenhydrinate (Gravol) can be incorporated with aprepitant for managing breakthrough nausea and vomiting 3

Dosing Considerations

• Standard oral aprepitant dosing for chemotherapy-induced nausea and vomiting is 125 mg on day 1, followed by 80 mg on days 2 and 3 3
• For postoperative nausea and vomiting, a single 40 mg dose has been shown to be effective 4, 5
• When using aprepitant with dexamethasone, the dexamethasone dose should be reduced due to drug interactions 3, 1

Drug Interactions

• Aprepitant is a substrate, moderate inhibitor, and moderate inducer of CYP3A4, and also induces CYP2C9 3, 1
• While aprepitant has potential for drug interactions, the combinations with ondansetron, metoclopramide, dimenhydrinate, and haloperidol are not contraindicated 3, 1
• Contraindicated combinations include pimozide, terfenadine, astemizole, and cisapride due to risk of serious reactions 3

Clinical Efficacy

• Aprepitant is particularly effective for preventing delayed emesis (25-120 hours after chemotherapy) compared to other antiemetics 3
• When combined with standard antiemetic therapy (5-HT3 antagonist plus dexamethasone), aprepitant significantly improves complete response rates 3, 6
• A single-dose regimen of intravenous fosaprepitant (150 mg) on day 1 is non-inferior to the 3-day oral aprepitant regimen 7

Important Considerations

• For breakthrough nausea and vomiting, the general principle is to add agents from different drug classes, which supports combining aprepitant with other antiemetics 3
• Preventing nausea and vomiting is generally more effective than treating established symptoms, so prophylactic use of aprepitant is recommended when indicated 3
• No studies show efficacy or safety of chronic dosing with aprepitant; the drug interaction profile may change with chronic use 3