The international prospective primary prevention study in hypertension (IPPPSH): objectives and methods. The IPPPSH Collaborative Group.

The International Prospective Primary Prevention Study in Hypertension (IPPPSH), an international multicentre randomised double-blind trial, compares antihypertensive regimens containing a beta-blocker (oxprenolol) with regimens not containing a beta-blocker. The protocol was developed and the study started in 1977. 6,357 patients fulfilled the inclusion criteria and were enrolled by the end of 1980. Patients have been treated in 6 countries for 3 to 5 years by 288 general practitioner and hospital out-patient centres. Follow-up was finished at the end of 1983 when 25,651 years of patient treatment had been completed. At entry patients had a diastolic pressure of 100-125 mmHg with no clinical evidence of cerebrovascular or ischaemic heart disease (W.H.O. Stages I and II hypertension). The study was designed to examine three main objectives: any influence of oxprenolol on the incidence of myocardial infarction and sudden death compared with antihypertensive therapy not containing a beta-blocker; the influence of cerebrovascular accidents in the same two groups; a comparison of the antihypertensive effectiveness, and the subjective and objective tolerability of the regimens. This paper summarises the objectives and methodology, and examines randomisation between the two treatment groups at entry into the IPPPSH.