Objective To describe characteristics of dosing history in patients prescribed a once a day antihypertensive medication. Design Longitudinal database study. Setting Clinical studies archived in database for [1989][1990][1991][1992][1993][1994][1995][1996][1997][1998][1999][2000][2001][2002][2003][2004][2005][2006]. Participants Patients who participated in the studies whose dosing histories were available through electronic monitoring. Main outcome measures Persistence with prescribed antihypertensive treatment and execution of their once a day drug dosing regimens. Results The database contained dosing histories of 4783 patients with hypertension. The data came from 21 phase IV clinical studies, with lengths ranging from 30 to 330 days and involving 43 different antihypertensive drugs, including angiotensin II receptor blockers (n=2088), calcium channel blockers (n=937), angiotensin converting enzyme inhibitors (n=665), β blockers (n=195), and diuretics (n=155). About half of the patients who were prescribed an antihypertensive drug had stopped taking it within one year. On any day, patients who were still engaged with the drug dosing regimen omitted about 10% of the scheduled doses: 42% of these omissions were of a single day's dose, whereas 43% were part of a sequence of several days (three or more days-that is, drug "holidays"). Almost half of the patients had at least one drug holiday a year. The likelihood that a patient would discontinue treatment early was inversely related to the quality of his or her daily execution of the dosing regimen. Conclusions Early discontinuation of treatment and suboptimal daily execution of the prescribed regimens are the most common facets of poor adherence with once a day antihypertensive drug treatments. The shortfalls in drug exposure that these dosing errors create might be a common cause of low rates of blood pressure control and high variability in responses to prescribed antihypertensive drugs. INTRODUCTIONHypertension is a major risk factor for the development of cardiovascular disease.1 2 Effective and well tolerated once a day antihypertensive drugs are now available. Yet poor adherence with prescribed treatment continues to be one of the main causes of unsatisfactory control of blood pressure and might lead to target organ damage and increased cardiovascular risk. 3-5 Although many studies have examined the "adherence issue" over many years, the absence of a common taxonomy and the lack of reliable measurements of ambulatory patients' exposure to prescribed pharmaceuticals have resulted in much confusion, with "adherence rates" ranging from 35% to as high as 97%. One aspect of the problem is that traditional methods (pill counts, questionnaires, patients' diaries, measurements of drug concentration in plasma, etc) have repeatedly been shown to overestimate adherence. 8 9A reliable assessment of the prevalence of poor adherence, including short persistence, can be inferred over long term follow-up from the timing of refills in large prescription databases,...

A pharmacy-led intervention can improve medication compliance in patients with moderate to severe heart failure, even in those with relatively high compliance. Future interventions should also focus at less compliant patients.