Inappropriate practices in prescribing:
Who decides and how?
CMAJ 1997;156:1696
See response by: P.J. McLeod, R.M. Tamblyn
McLeod and colleagues ("Defining inappropriate practices in prescribing for elderly people: a national consensus panel,", CMAJ 1997;156:385-91 [full text / résumé]) state that dipyridamole should not be prescribed to prevent stroke because it is ineffective for this indication. In this regard, I would like to inform readers of the results of a recent clinical trial.1
In the study, 6602 patients with a mean age of 66.7 years who had had a previous stroke or transient ischemic attack (TIA) were randomly assigned to receive ASA (50 mg daily), modified-release dipyridamole (400 mg daily), a combination of the 2 agents or a placebo. This was a blinded study, and patients were followed for 2 years. The relative reduction in the risk of stroke from taking ASA was 18.1% (p = 0.013), from taking dipyridamole was 16.3% (p = 0.039) and from taking the combination, 37% (p < 0.001), compared with placebo.
The combination was significantly more effective than either agent alone. The authors concluded that "ASA 25 mg twice daily and dipyridamole, in a modified-release form, at a dose of 200 mg twice daily have each been shown to be equally effective for the secondary prevention of ischemic stroke and TIA; when coprescribed the protective effects are additive, the combination being significantly more effective than either agent prescribed singly; and low-dose ASA does not eliminate the propensity for induced bleeding."
The formulation of dipyridamole used in this study is not available in Canada, and stroke prevention is not an approved indication for this product in this country.
Frederick Vickerson, PhD
Head
Medical Services
Boehringer Ingelheim (Canada) Ltd.
Burlington, Ont.
Reference
- Diener H, Cunha L, Forbes C, et al. European Stroke Prevention Study 2: dipyridamole and acetylsalicylic acid in the secondary prevention of stroke. J Neurol Sci 1996;143:1-13.
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