EDITOR—The clinical research edition of the 13 June issue of the BMJ contained an advertisement for Didronel PMO (between pages 1764 and 1765). The advertisement claimed that the combination tablet of disodium etidronate 400 mg and calcium carbonate 1250 mg “is proven and licensed to protect bones from corticosteroid induced osteoporosis.” However, the data presented to support this statement—that is, that “initiating this treatment at the start of long-term corticosteroid therapy reduces the incidence of new vertebral fractures in postmenopausal women on high dose corticosteroids by 85% compared to control (p=0.19)”—does not provide evidence of benefit. 1 2 Although we recognise that a non-significant effect does not mean that there is no effect, the absence of confidence intervals does not allow clinical significance to be evaluated.3

The supporting references by Adachi et al1 and correspondence in the New England Journal of Medicine 2 4 add further confusion. These references indicate that: the study was not designed to show the effect of disodium etidronate on the incidence of fractures (a secondary endpoint) 1 2 ; a treatment effect was seen only in postmenopausal women1; and there seemed to be a greater frequency of vertebral fractures occurring among men in the group taking disodium etidronate (4 of 19 men …