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Executive Summary

Merrell Dow Seldane (terfenadine) caused drowsiness in clinical trials at about the same frequency as did placebo, according to the FDA-approved labeling for the drug. The agency approved Seldane as an Rx oral antihistamine on May 8 after a three year NDA review. The approved labeling for the drug states that in the four largest clinical trials, "the frequency of drowsiness with Seldane was similar to the frequency with placebo." In the four trials, the labeling states, "about 50-70% of Seldane or other antihistamine recipients had moderate to complete relief of symptoms, compared with 30-50% of placebo recipients, with a significant difference favoring the active drugs in each study. In these studies, Seldane was associated with less frequent drowsiness than the other antihistamines." The labeling notes that "the four best controlled and largest trials each lasted seven days and involved about 1,000 total patients in comparisons of Seldane (60 mg b.i.d.) with an active drug (chlorpheniramine, 4 mg b.i.d.; dexchlorpheniramine, 2 mg b.i.d.; or clemastine 1 mg b.i.d.)." Seldane is indicated "for the relief of symptoms associated with seasonal allergic rhinitis such as sneezing, rhinorrhea, pruritus and lacrimation." The labeling notes that there are no adequate and well controlled trials in women during pregnancy or lactation. Safety and effectiveness of Seldane in children under 12 years of age has also not been established, the labeling states. The price to whslrs. is $43.21 for a bottle of 100 60 mg tablets, Merrell Dow said. The firm estimates that the cost to the patient for a two week b.i.d. supply of Seldane will range from $15 to $18. Merrell Dow said that it would begin shipping the Rx by air to whslrs. on May 15. In an HHS press release announcing the approval of Seldane, FDA Com. Young, stated that "this first representative of a new class of non-sedating antihistamines can be seen as important because it can reduce an often troublesome side effect." Merrell Dow has a marketing advantage in being the first to have a non-sedating antihistamine approved by the agency. Janssen's Hismanal (astemizole), also lacking the sedative characteristics common with most antihistamines, is in Phase III clinicals in the U.S. and currently marketed in the U.K. In a Merrell Dow sponsored teleconference, James Kemp, MD, University of California, San Diego, discussed the pharmacologic differences between Seldane and astemizole. Kemp said: "It's an entirely different molecule. As far as the main differences are concerned, it is my perception that terfenadine has a faster onset of action and a shorter half-life. One of the potential problems with astemizole -- I know this is true in the FDA's mind -- is its very long half-life which in many cases means it takes over a week to get it out of the body once a person has taken it." Kemp added that the long half-life of astemizole "proves to be a side effect for the allergist as far as doing allergy testing in that this antihistamine binds so [strongly] to the receptors that indeed it would make skin testing very difficult for us." Seldane labeling states that pharmacokinetic studies in 27 male subjects found that "following administration of a single 60 mg Seldane tablet, detectable plasma levels reached peak at about 2 hours after administration; a distribution half-life of 3-4 hours was followed by an elimination half-life of 20-25 hours." Seldane is the second Merrell Dow Rx drug which is targeted at a broad patient base which is more typical of OTC products. The firm's original mass market Rx product is the antismoking product Nicorette, which was introduced in December 1982. HHS' release notes that Seldane "will be sold for relieving seasonal allergic rhinitis" which affects 40 mil., or "one in six Americans, who spend more than $500 mil. yearly for relief." FDA approved Seldane as a Class 1B drug, that is, a new molecular entity (1) with a modest therapeutic gain (b). The product is currently sold in over 20 countries, Merrell Dow press material notes. Merrell Dow will also be seeking an indication for children under 12. Kemp commented that "clinical studies have been completed in children but as yet the FDA has not approved its use." He suggested that FDA approval for children "wouldn't . . . be very long in coming."

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