[A population-based study of need for changes and continuing rates of antihypertensive drugs]. / Análisis poblacional de la necesidad de cambios y tasas de continuidad de los diferentes fármacos antihipertensivos.

BACKGROUND: Antihypertensive drugs are frequently changed because of inefficacy and adverse effects. The aim of this study was to compare the incidence of changes of the new classes of drugs from the classical beta-blockers and diuretics. We also have calculated the probability of continuing with each class of drug. MATERIAL AND METHOD: Clinical reports of hypertensive patients of a general practice centre were examined. All changes of treatment and their causes were registered between october 1997 and september 1999. The incidences for global changes and also for intolerance and inefficacy changes were calculated for each drug. Relative risks for beta-blockers, diuretics, ACE inhibitors of anhidride carbonic enzyme and angiotensine II-receptor-antagonists were analized. The cumulated probability for continuing therapy was also studied. RESULTS: 27.6% out of 786 courses of treatment were changed, 51.4% due to intolerance and 29,8% due to inefficacy. The probability for continuing was 88% after 3 months, 81% after 6 months, 71% after one year and 54% after 2 years. The probability for discontinuing because of intolerance was higher in the first 3 months (51%), but afterwards it remained stable along the time. CONCLUSIONS: Antihypertensive drugs are discontinued more frequently than what it would be desirable and their continuing rates are low. Differences observed among each class of drugs are not argument enough for changing the general recommendation of using beta-blockers and diuretics as first choice drugs for initial treatment of hypertension.