The Nordic Diltiazem Study (NORDIL). A prospective intervention trial of calcium antagonist therapy in hypertension.

NORDIL--the Nordic diltiazem intervention study was started in September 1992. This trial is a prospective randomized open blinded-endpoint (PROBE) multicenter, parallel-group study conducted in Norway and Sweden. The study is designed to evaluate the potential preventive effects of diltiazem compared with conventional antihypertensive drug treatment. Primary endpoints are cardiovascular mortality defined as fatal acute myocardial infarction, fatal acute cerebrovascular disease (stroke), sudden death and other fatal cardiovascular disease as well as cardiovascular morbidity defined as myocardial infarction and cerebrovascular disease (stroke). Secondary endpoints are total mortality, the development or deterioration of ischaemic heart disease, congestive heart failure, atrial fibrillation, transient ischaemic attacks, diabetes mellitus and renal insufficiency. Male and female patients, aged 50-69, with primary hypertension are randomly allocated to therapy starting with either diltiazem (180-360 mg daily) or conventional treatment (diuretics or beta-adrenergic blockers). Add-on therapy in the conventional treatment group excludes all types of calcium antagonists. The goal of treatment will be a target diastolic blood pressure of < or = 90 mmHg or a 10% diastolic blood pressure reduction. The NORDIL study will allow the detection of a 20% difference in cardiovascular mortality between the two groups with a power of 80% at the 5% significance level (two-sided test). A total of 12,000 patients will be recruited from about 480 primary Health Care Centers or hospital based Hypertension Units. Patients will be treated for an average period of 5 years.