Aprepitant - A review of its use in the prevention of chemotherapy-induced nausea and vomiting

Aprepitant (Emend(R)) is the first commercially available drug from a new class of agents, the neurokinin NK1 receptor antagonists. Oral aprepitant, in combination with other agents, is indicated for the prevention of acute and delayed chemotherapy-induced nausea and vomiting (CINV) associated with highly emetogenic chemotherapy in adults. In three randomised, double-blind, placebo-controlled trials comparing aprepitant (125mg day 1, 80mg once daily on days 2 and 3 or 2-5) plus standard therapy (intravenous ondansetron and oral dexamethasone) with standard therapy plus placebo, overall complete responses (primary endpoint, defined as no emesis and no rescue therapy) were seen in significantly more patients in the aprepitant arms (63-73% versus 43-52%, p < 0.01 for all comparisons). Complete responses and complete protection during the acute and delayed phase, and overall complete protection were also observed in significantly more patients in the aprepitant arms. The difference between treatment groups was more marked in the overall and delayed phases than in the acute phase. The antiemetic efficacy of aprepitant plus standard therapy in the prevention of CINV was maintained for up to six cycles of chemotherapy. Where assessed, more patients in the aprepitant plus standard therapy arms than the standard therapy plus placebo arms reported no impact of CINV on daily life, as assessed by the Functional Living Index-Emesis. Aprepitant is generally well tolerated. The most common adverse events in randomised trials were asthenia or fatigue. Other adverse events experienced by aprepitant recipients include anorexia, constipation, diarrhoea, nausea (after day 5 of the study) and hiccups. In addition to being a substrate for cytochrome P450 (CYP) 3A4, aprepitant is also a moderate inhibitor and inducer of this isoenzyme as well as an inducer of CYP2C9. Thus, aprepitant has the potential to interact with other agents metabolised by hepatic CYP isoenzymes. In one trial, there was a higher incidence of serious infection or febrile neutropenia in the aprepitant plus standard therapy arm than the standard therapy plus placebo arm; this was attributed to a pharmacokinetic interaction between aprepitant and dexamethasone. In subsequent trials, a modified dexamethasone regimen was used. In conclusion, when added to standard therapy (a serotonin 5-HT3 receptor antagonist and a corticosteroid), aprepitant is effective and generally well tolerated in the prevention of CINV associated with highly emetogenic chemotherapy in adults. Despite marked advances in the prevention of CINV, standard therapy does not protect all patients. The addition of aprepitant to standard therapy provides an advance in the prevention of both acute and delayed CINV in adults with cancer.