FDA Approves New Type of Antiemetic for Cancer Patients
Aprepitant prevents the onset of nausea and vomiting by binding to neurokinin type 1 receptors on brain cells. These receptors mediate the actions of substance P, a peptide that increases the contractions of involuntary muscles in the gastrointestinal tract and dilates blood vessels. According to the product's labeling, aprepitant does not bind appreciably to receptors for corticosteroids, serotonin type 3 (5-HT3), or dopaminethe sites critical to the actions of other drugs commonly used to prevent nausea and vomiting.
The labeling for aprepitant states that the drug is to be used with a corticosteroid and a 5-HT3 antagonist in an effort to prevent, not treat, the nausea and vomiting that occur initially and during the first five days after therapy with highly emetogenic cancer drugs, such as cisplatin given in high doses.
During the clinical studies of aprepitant, the drug was administered with oral dexamethasone and intravenous ondansetron on the first day of a course of cancer chemotherapy and with dexamethasone but not ondansetron on the second and third days; dexamethasone was given alone on the fourth day. The recommended dosage of aprepitant is 125 mg one hour before receipt of highly emetogenic chemotherapy and 80 mg on the first two mornings afterward; aprepitant is not to be taken continuously throughout the chemotherapy cycle.
Because aprepitant moderately inhibits the action of cytochrome P-450 isoenzyme 3A4, the drug should not be used with pimozide, terfenadine, astemizole, or cisapride. Aprepitant's labeling also suggests that patients taking warfarin have their clotting status closely monitored after every three-day treatment with the antiemetic, particularly on days 7 and 10, and that patients taking an oral contraceptive use another means of birth control. The antiemetic also induces cytochrome P-450 isoenzyme 2C9.
According to the company, the most frequently reported adverse reactions during the clinical studies of aprepitant were fatigue, constipation, diarrhea, anorexia, nausea, and hiccups.
Merck said Emend will first be available in pharmacies the week of April 14.
Although the company said the typical patient would bring one Emend trifold package, containing one 125-mg capsule and two 80-mg capsules, to the hospital clinic or physician office on the day that the highly emetogenic chemotherapy is to be administered, the two capsule strengths will also be available in 30-count bottles and 5-count unit dose packages. The labeling states that the desiccant provided in the 30-count bottles should not be removed from those containers.