SMITHKLINE BEECHAM's SEROXAT ANTIDEPRESSANT LAUNCHED IN U.K.

SMITHKLINE BEECHAM's SEROXAT ANTIDEPRESSANT LAUNCHED IN U.K. on Feb. 7 for "all types of depressive illness, including depression accompanied by anxiety," according to approved labeling. The U.K. approval in December 1990 was SmithKline Beecham's first for the 5HT uptake inhibitor. Seroxat (paroxetine), which is indicated for once-daily dosing, will compete against Lilly's drug of the same class, Prozac (fluoxetine). The U.K. government has approved a price for Seroxat at a 15.3% premium to Prozac. On a per-day basis (dosing once a day), SKB's product is (BRITISH POUND) 1.13 compared to 98 pence for Prozac. The paroxetine U.K. labeling reveals several potential advantages over Prozac in the side effect profile. For example, Seroxat does not result in anorexia, which was seen in 13% of patients in Prozac clinical trials. Also, the SKB product has a shorter elimination half-life and achieves a steady state plasma concentration more quickly. U.K. labeling lists side effects seen in paroxetine clinical trials as: "nausea, somnolence, sweating, tremor, asthenia, dry mouth, insomnia and sexual dysfunction." Anorexia or other gastrointestinal complaints are not listed as side effects. The drug's elimination half-life is "generally about one day" and "steady state systemic levels are attained by seven-14 days," U.K. labeling states. Paroxetine was studied in approximately 4,000 patients worldwide. By comparison, labeling for Prozac as it is approved in the U.S. lists the most frequently observed adverse events as: "nervous system complaints, including anxiety, nervousness and insomnia; drowsiness and fatigue or asthenia; tremor; sweating; gastrointestinal complaints, including anorexia, nausea and diarrhea; and dizziness or lightheadedness." Half-life elimination is "relatively slow . . . two to three days," and steady state plasma concentrations "are only achieved after continuous dosing for weeks," labeling states. Lilly studied Prozac in more than 5,600 patients in the U.S. prior to its approval in late 1987. Both 5HT serotonin uptake inhibitors contain similar warnings sections -- avoid combined use with MAO inhibitors. Prozac, however, carries a warning that an approximately 4% incidence of rash and/or urticaria was seen in clinical trial participants. SmithKline Beecham filed an NDA in November 1989 for paroxetine in the U.S. where it will be marketed under the tradename Aropax. The company is also pursuing an antianxiety indication. Comparative trials with fluoxetine are underway. One of SmithKline's top R&D people alluded to the side effect comparison at an R&D update to the U.S. investment community in the spring of 1990. SKB Development Project Director Tim Melton, PhD, asserted that paroxetine appears to have several advantages over Prozac, including reduced side effects such as anorexia, nervousness and anxiety as well as a quicker wash-out period ("The Pink Sheet" April 9, p. 9). At the time, the company had no head- to-head studies with Prozac.