Aprepitant: A substance P antagonist for chemotherapy induced nausea and vomiting

The episodes of nausea and vomiting which follow each cycle of chemotherapy are the most troublesome side effect experienced by cancer patients. Introduction of ondansetron was a definite therapeutic advance in treating chemotherapy induced nausea and vomiting (CINV) with more effectiveness with corticosteroids. However, the protection remained largely limited to acute phase of CINV with little or no effect over delayed phase. Aprepitant, a drug that antagonizes the effect of substance P on neurokinin type 1 receptor showed promising results in controlling both phases of CINV. This drug is well absorbed orally with a t_max of about four hours. The addition of aprepitant to ondansetron and dexamethasone was found to be superior to ondansetron and dexamethasone alone in clinical trials with patients taking high and moderate emetogenic chemotherapy. This drug also showed a good safety profile, but its inhibitory effect on CYP3A4 may result in clinically significant drug interactions needing dose modifications of co-administered drugs. The National Comprehensive Cancer Network guidelines for CINV recommends the use of aprepitant with high and moderately emetogenic anticancer drugs. Results of ongoing clinical trials with aprepitant and other agents of this new class of antiemetics are awaited and may alleviate the sufferings of cancer patients.

Keywords
Antiemetics, aprepitant, chemotherapy induced nausea and vomiting, neurokinin