Factors influencing adherence to antihypertensive therapy in Italy

Background: Antihypertensives (AHs) are the main drug class both for prevalence of use and costs in Western Countries. Continuity of use is an important factor influencing the success of these therapies, but low adherence by patients has been frequently observed. Objectives: To identify potential predictors of continuity of drug use and of blood pressure target values achievement. Methods: Data on drug prescriptions, clinical events, diagnoses, hospital admissions and causes of death on 600,000 Italian subjects (400 GPs) were collected from the Health Search Database. Patients with a diagnosis of hypertension before 2004 were selected and their 2004–05 data were analysed. Patients who received an amount of AHs consistent with daily use were defined continuous. Results: Overall, 63,260 hypertensive patients were selected. Females were 59% and the average age was 66. Sixty-two percent had hypertension diagnosis in the last 5 years, 16% were diabetics, 8% had cerebrovascular accidents; 60% had no smoking history. During 2005, 6% withdrew their treatment (especially in case of recent diagnosis) and 35% did not take drugs continuously, more frequently in case of diuretics and -blockers, recent diagnosis, absence of diabetes and of previous ictus/TIA. Among continuous patients, 51% achieved a good control of hypertension without dose or drug changes, 23% changed drugs (especially among diabetic patients and those with previous ictus/TIA), 24% changed doses (more frequently in case of Ca channel blockers and ACE inhibitors) and 2% of subjects resulted continuous for drugs and doses without achieving target pressure values. Conclusions: In 2005, only 1/3 of patients receiving AHs were continuous and had well controlled blood pressure. Older diagnosis of hypertension, concomitant diabetes and use of specific drugs (Ca channel blockers, ACE inhibitors or angiotensin antagonists) positively influenced continuity of use of AHs.