Study population and treatment titration in the International Nifedipine GITS Study: Intervention as a Goal in Hypertension Treatment (INSIGHT)

Objectives To ascertain the baseline characteristics of the high-risk hyper tensive patients entering the International Nifedipine GITS Study: Interven tion as a Goal in Hypertension Treatment (INSIGHT), To determine the succes s of single and combination therapy in achieving target blood pressures in such a population. Design INSIGHT is a double-blind, prospective outcome trial comparing the e fficacy of the calcium channel blocker, nifedipine GITS, and the thiazide, co-amilozide, in preventing myocardial infarction and stroke. We recruited 2996 men and 3454 women, aged 55-80 years, with blood pressure during place bo run-in >150/95 mmHg or isolated systolic blood pressure >160 mmHg from n ine countries. Treatment allocation to nifedipine GITS 30 mg daily or co-am ilozide (hydrochlorothiazide 25 mg/amiloride 5 mg) once daily was performed by minimization rather than randomization to balance additional risk facto rs. This was followed by four optional increases in treatment: dose-doublin g of the primary drug, addition of atenolol 25/50 mg or enalapril 5/10 mg, and then any other hypotensive drug excluding calcium blockers or diuretics . Target blood pressure was 140/90 mmHg or a fall greater than or equal to 20/10 mmHg. Results Blood pressure at randomization was 172 +/- 15/99 +/- 9 mmHg. Thirt een per cent of the patients were previously untreated. The proportions of each additional risk factors were: smoking >10/day, 29%; cholesterol > 6.43 mmol/l, 52%; family history of premature myocardial infarction or stroke, 21%; diabetes mellitus 20%; left ventricular hypertrophy, 10%; previous myo cardial infarction, other presentations of coronary heart disease, and peri pheral vascular disease, each 6%; proteinuria, 3%. Fifty-five per cent of p atients had one additional risk factor, whereas 33%, 9% and 3% had two, thr ee or more additional risk factors, respectively. The blood pressure land f alls in blood pressure) at the end of titration and at 1 year after minimiz ation was 139 +/- 12/82 +/- 7 mmHg (33 +/- 15/17 +/- 9) in the 5226 patient s still on randomized treatment. The numbers requiring the four treatment i ncrements were, respectively, 1591, 780, 597 and 294, meaning that almost 7 0% of patients on randomized treatment in INSIGHT are receiving only the pr imary drug. At one year, 69% of patients had a blood pressure less than or equal to 140/90 mmHg, Conclusion INSIGHT is one of the first double-blind comparisons of active a ntihypertensive treatments, requiring high-risk patients to achieve suffici ent power. Despite this requirement, it is possible to achieve good blood p ressure control in most patients without the addition of multiple additiona l treatments that may dilute any differences between the primary agents. J Hypertens 1998, 16:211 3-2116 (C) 1998 Lippincott Williams & Wilkins.