Benefits of adherence to anti-hypertensive drug therapy

Long-term adherence or compliance with antihypertensive drug therapy is poor. It has been estimated that within the first year of treatment 16-50% of hypertensives discontinue their anti-hypertensive medications. Even among those who remain on therapy long term, missed medication doses are common. Epidemiological studies have shown that drug-treated hypertensives have higher blood pressures than age-, gender- and body mass index-matched normotensives. In addition, drug-treated hypertensive men and women who achieve blood pressure normalization are less likely to die over a 9.5-year period than those whose blood pressure remains elevated while taking anti-hypertensive drugs. Thus, one reason for less than optimal reduction of blood pressure-related cardiovascular-renal risk in drug-treated hypertensives is inadequate blood pressure lowering. Quantifiable excess risk has been documented even in the short term (<1 year) after interruption or discontinuation of anti-hypertensive medications as total healthcare costs are higher, mostly because of higher hospitalization rates. Data from the Treatment of Mild Hypertension Study (TOMHS) are relevant to long-term adherence to various anti-hypertensive drug monotherapies. At 48 months, 82.5% and 77.8% of participants remained on amlodipine and acebutolol, respectively (both P<0.01 compared with placebo). However, only 67.5%, 66.1% and 68.1%, respectively, of chlorthalidone, doxazosin and enalapril participants remained on these drugs as monotherapy at 48 months. Differential adherence to long-term anti-hypertensive drug therapy could translate into a greater risk of blood pressure-related complications and higher overall healthcare expenditures. Strategies to minimize the deleterious impact of therapeutic non-adherence with anti-hypertensive medications as well as the clinical and cost implications of the TOMHS data will be discussed.