PubMed · 8893619
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T E David, V L Gott, L A Harker, G E Miller, D C Naftel, A G Turpie. 1996. Mechanical valves.. https://doi.org/10.1016/0003-4975(96)82420-9
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BACKGROUND: Patients with transient ischaemic attacks (TIA) and minor ischaemic strokes are at risk of serious vascular events (death from all vascular causes, non-fatal stroke, or non-fatal myocardial infarction). Their risk of vascular events lies between 4 and 11 percent per year. Aspirin only, in a daily dose of 30 mg or more, offers only modest protection in such patients: it reduces the incidence of major vascular events by 13 percent. In a single trial, adding dipyridamole (an alternative antiplatelet agent) to aspirin was associated with a 22 percent reduction in the risk of major vascular events compared with aspirin alone. However, a systematic review of all trials of antiplatelet agents by the Antithrombotic Trialists' Collaboration showed that, in high risk patients, there was virtually no difference between the aspirin-dipyridamole combination and aspirin alone. We therefore sought to assess the effects of dipyridamole in more detail. OBJECTIVES: 1) To assess the efficacy of dipyridamole versus control in the secondary prevention of vascular events in patients with vascular disease in the presence and absence of other antiplatelet drugs. 2) To assess the safety of dipyridamole versus control in the secondary prevention of vascular events in patients with vascular disease in the presence and absence of other antiplatelet drugs. SEARCH STRATEGY: The Cochrane Stroke Group Trials Register was searched and other relevant Cochrane Groups were contacted to search their specialised registers (last search 29 April 2002). In addition the Cochrane Controlled Trials Register, MEDLINE and EMBASE were searched and Dutch manufacturers of dipyridamole were contacted to identify further published and unpublished studies. SELECTION CRITERIA: Randomised long term secondary prevention trials with concealed treatment allocation, treatment for > 1 month, starting within 6 months after presentation of a arterial vascular disease were selected (coronary artery disease, myocardial infarction, angina pectoris, retinopathy, nephropathy, peripheral arterial disease, stroke, TIA, amaurosis fugax). Therapy consisted of dipyridamole in any dose in the presence or absence of other antiplatelet drugs compared with no drug or an antiplatelet drug(s) other than dipyridamole (control group). DATA COLLECTION AND ANALYSIS: Two reviewers selected trials which met the inclusion criteria and extracted details of randomisation methods, blinding of treatments and assessments, whether intention-to-treat analysis was possible from the published data, whether treatment groups were comparable with regard to major prognostic factors, the number of patients who were excluded or lost to follow-up, definition of outcome events, and entry and exclusion criteria. The methodological quality of each trial was assessed by the two reviewers on the basis of these extracted data. In addition, dose and type of antiplatelet treatments, duration of follow-up and the numbers of defined outcome events were recorded. Data published by the Antithrombotic Trialists' Collaboration were used. The remaining data were independently extracted by the same two reviewers and cross checked. Data were analysed according to the intention-to-treat principle. Relative and absolute risk reductions were calculated by means of the statistical software provided by the Cochrane Collaboration (RevMan). MAIN RESULTS: Twenty-six trials were included, with a total of 19842 patients, among whom 1399 vascular deaths and 3085 fatal and non-fatal vascular events occurred during follow-up. Compared with control, dipyridamole had no clear effect on vascular death (RR 1.02, 95% CI 0.90 to 1.17). This result was not influenced by the dose of dipyridamole or type of presenting vascular disease. Compared with control, dipyridamole appeared to reduce the risk of vascular events (RR 0.90, 95% CI 0.83 to 0.98), but this effect was only statistically significant due to a single large trial in patients presenting with cerebral ischaemia (6602 patients). Comparing dipyridamole plus aspirin with aspirin alone: there was no clear difference in vascular death, the RR was 1.03 (95% CI 0.87 to 1.22); the combination was associated with fewer vascular events with an RR of 0.90 (95% CI 0.80 to 1.00). Combination treatment of dipyridamole and aspirin compared with placebo had an RR of 0.89 (95% CI 0.79 to 1.01) for vascular death and an RR of 0.74 (95% CI 0.68 to 0.80) for vascular events. REVIEWER'S CONCLUSIONS: This review found that, for patients who presented with arterial vascular disease, there was no evidence that dipyridamole, in the presence or absence of an other antiplatelet drug (chiefly aspirin) reduced the risk of vascular death, though it may reduce the risk of further vascular events. However, this benefit was found in only a single large trial and only in patients presenting after cerebral ischaemia. There was no evidence that dipyridamole alone was more efficacious than aspirin. Further trials comparing the effects of the combination of dipyridamole with aspirin with aspirin alone are justified.
BACKGROUND: In the initial treatment of venous thromboembolism (VTE) low molecular weight heparin (LMWH) is administered once or twice daily. A once daily treatment regimen is more convenient for the patient and may optimise home treatment. However it is not clear whether a once daily treatment regimen is as safe and effective as a twice daily treatment regimen. OBJECTIVES: The objective of this review was to compare the efficacy and safety of once daily administration to a twice daily administration of LMWH. SEARCH STRATEGY: Trials were identified through the Specialised Register of the Cochrane Peripheral Vascular Diseases Group (last searched May 2001), the Cochrane Controlled Trials Register (CCTR/CENTRAL) (last searched Issue 1, 2002), by hand-searching other relevant journals, by checking cross-references and through personal communication with experts. SELECTION CRITERIA: Randomised clinical trials in which a once daily treatment regimen with LMWH is compared to a twice daily regimen in the initial treatment of patients with venous thromboembolism. DATA COLLECTION AND ANALYSIS: Two reviewers assessed trials on criteria for inclusion and extracted the data independently. MAIN RESULTS: Five studies were included with a total of 1508 patients. The pooled data showed a statistically non-significant difference in recurrent venous thromboembolism between the two treatment regimens (OR 0.82; 0.49 - 1.39). A comparison of major haemorrhagic events (OR 0.77; 0.40 - 1.45) and mortality (OR 1.14; 0.62 - 2.08) also showed a statistically non-significant difference between the two treatment regimens. REVIEWER'S CONCLUSIONS: Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH. However, the 95% confidence interval implies that there is a possibility that the risk of recurrent VTE might be higher when patients are treated once daily. Hence the decision to treat the patient with a once daily regimen will depend on the evaluated balance between increased convenience and the potential for a lower efficacy.