Concomitant medication use in postmenopausal women using estrogen therapy

Objective: To determine whether long-term postmenopausal estrogen therapy i s associated with use of other prescription medications. Methods: Using computer pharmacy records from 1969 to 1973 for members of t he Kaiser Permanente Medical Care Program in San Francisco, we identified t he 215 most commonly used prescription medications in the pharmacy database and recorded their use by 232 postmenopausal long-term estrogen users and by 222 postmenopausal age-matched nonusers. These medications were grouped into 39 therapeutic classes. Classes of medications used by estrogen users and non-users were compared. Results: A statistically significant difference in use was seen for 21 of t he 39 medication classes; of these 21 classes, 20 (95%) were used more freq uently and 1 less frequently by estrogen users. Differences between estroge n users and nonusers were greatest for thyroid hormone preparations (estrog en user/nonuser multivariate odds ratio = 25.6, 95% confidence interval 5.9 -112) and anti-migraine preparations (11 recipients among estrogen users, n one among nonusers). Postmenopausal women using estrogen were more likely t han nonusers to use additional medications. Conclusion: Greater use of certain prescription medications by estrogen use rs than by nonusers should be considered in studying the health effects of estrogen replacement therapy.