Rauwolfia use and breast cancer: a case-control study.

Breast cancer risk among 1,362 cases and 1,250 controls participating in a large multicenter screening program was examined in relation to hypertension and the use of rauwolfia derivatives. A previous diagnosis of hypertension, reported by 22% of the cases and 23% of the controls, was not associated with an increased risk of breast cancer [odds ratio (OR) = 0.9]; nor was there any excess risk for long-term hypertensives. In addition, there was no significant increase in risk associated with use of either rauwolfia derivatives (OR = 1.2), thiazide preparations (OR = 1.2), or methyldopa (OR = 1.1). However, there were significant excess risks among long-term users and those with extended intervals since first use of rauwolfia. Rauwolfia users of 10 or more years' duration or those whose initial use occurred greater than or equal to 10 years before diagnosis had risk ratios of 4.5 (95% Cl, 1.2-19.8) and 3.8 (95% Cl, 2.3-11.6), respectively. These results suggest that women exposed to long-term rauwolfia use have an elevated risk of developing breast cancer, although the results fail to support previous observations of a generalized adverse effect.