Continuation of postmenopausal hormone replacement therapy in a large health maintenance organization: Transdermal matrix patch versus oral estrogen therapy

Objective: To determine possible differences in continuation of postmenopau sal estrogen replacement therapy among women initiating treatment with tran sdermal estradiol versus those initiating treatment with oval estrogen. Study Design: A retrospective database search. Patients and Methods: We analyzed estrogen use among 45- to 74-year-old wom en who filled index prescriptions for estrogen during 1996 for either once- a-week transdermal estradiol or daily oral estrogen. Prescription use was a nalyzed separately for each of 2 groups: 276 hysterectomized women who fill ed prescriptions for estrogen alone (ERT) and 4182 women who filled prescri ptions for medroxyprogesterone acetate (MPA) with estrogen (HRT) on the sam e day. Results: Risk of discontinuing therapy after 12 months ranged from 59% to 7 6% among the 4 subgroups: ERT with unopposed transdermal estradiol; ERT wit h unopposed oral estrogen; HRT with MPA-opposed transdermal estradiol; and HRT with MPA-opposed oral estrogen. The relative risk (RR) of discontinuati on was significantly greater among women starting HRT with transdermal estr adiol than among women starting oral estrogen (RR = 1.5; 95% confidence int erval [CI] = 1.3 to 1.8). RR of discontinuation among women starting ERT wi th transdermal estradiol compared with women starting oral estrogen therapy was 1.3 (95% Cl = 1.0 to 1.8). Conclusions: Approximately 2 of 3 women who start either ERT or HRT discont inue therapy within a year, regardless of hysterectomy status. Furthermore, women who start ERI or HRT with a transdermal estradiol system are more li kely to discontinue therapy.