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Executive Summary

Warner-Lambert's oral quinolone antibiotic Penetrex (enoxacin) was approved for urinary tract infections and gonorrhea Dec. 31, after a year of discussions between the company and FDA over three additional indications that are not covered in the approval. The drug was approved for the treatment of uncomplicated urethral or cervical gonorrhea, for uncomplicated urinary tract infections due to Escherichia coli, Staphylococcus epidermidis, or Staphylococcus saprophyticus, and for complicated urinary tract infections due to Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus epidermidis or Enterobacter cloacae. Warner-Lambert's NDA (19-616), submitted in October 1986, has been considered "approvable" by FDA since December 1990. The company had sought approval for upper and lower respiratory tract infections and skin infections as well as genital and urinary tract infections. At a meeting of securities analysts in April, Warner-Lambert Exec VP and President-U.S. Operations Lodewijk de Vink said that approval had been held up pending "discussions" on the labeling, which he said "ought to be broader based on our clinical data" ("The Pink Sheet" April 29, p. 8). At that time, analysts asked if Penetrex would be "viable" if the company was unsuccessful in getting its broad labeling. While former Chairman and CEO Joseph Williams responded that "we just are not satisfied with the labeling as it is," he added that "we'll come to a satisfactory conclusion and then we'll get on with it." The approved labeling states that "enoxacin exhibits in vitro minimum inhibitory concentrations (MICs) of 2.0 mcg/mL or less" against 14 gram-negative aerobes beyong the organisms covered by the approval. The labeling adds, however, that "the safety and effectiveness of enoxacin in treating clinical infections due to these organisms have not been established in adequate and well- controlled trials." Warner-Lambert would not disclose its plans on whether to continue to pursue additional indications for the drug, nor would the company comment on the price or launch date of the drug. Penetrex, which was licensed from the Japanese firm Dainippon Pharmaceutical, was approved with a "1C" rating (new molecular entity with little or no therapeutic gain over existing therapies). The drug was approved in 200 mg and 400 mg tablet doses. A single 400 mg dose is recommended for treatment of gonorrhea, 200 mg b.i.d. for seven days for uncomplicated urinary tract infections and 400 mg b.i.d. for 14 days for complicated urinary tract infections. Labeling notes adverse reactions and contraindications similar to those of other quinolones. The labeling warns against a "significant drug/drug interaction with theophylline and caffeine," and notes that concomitant bismuth subsalicylate decreased enoxacin bioavailability by about 25%. The labeling also notes that "moderate-to-severe phototoxicity reactions have been observed in patients exposed to direct sunlight while receiving enoxacin or some other drugs in this class." Direct sunlight should be avoided and therapy should be discontinued if phototoxicity develops, labeling says. The approved labeling also states: "Patients treated with enoxacin should have a follow-up serologic test for syphilis after 3 months" of being treated for gonorrhea, since the drug "has not been shown to be effective" for syphilis and "may mask or delay the symptoms of incubating syphilis." Elderly patients (65 years of age or more) experienced "significantly more overall adverse events" than patients under 65, the labeling also notes. Adverse events considered likely to be drug related, according to the labeling, were "nausea and/or vomiting 6%, dizziness 2%, headache 1%, abdominal pain 1%, diarrhea 1%, [and] dyspepsia 1%."

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