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  • Comparison of Angiotensin II ReceptorBlockers: Impact of Missed Doses of

    Candesartan Cilexetil and Losartan inSystemic Hypertension

    Giuseppe Mancia, MD, Raffaella DellOro, MD, Carlo Turri, MD, and Guido Grassi, MD

    Blood pressure remains poorly controlled in the hyper-tensive population due in large part to low or unsatis-factory patient compliance. Clinical studies that incorpo-rate an intentionally missed dose have been designed toevaluate the impact of poor patient compliance on theeffectiveness of antihypertensive medications. In thesestudies, ambulatory blood pressure monitoring is con-tinued throughout the dosing interval and beyond inorder to determine when systolic and diastolic bloodpressure increase into the hypertensive range. In an8-week, randomized, double-blind, placebo-controlledtrial in patients with mild-to-moderate hypertension, theantihypertensive effects of candesartan cilexetil 16 mgwere maintained after a missed dose, whereas systolicand diastolic blood pressure increased toward baseline

    levels after a missed dose of losartan 100 mg. Cande-sartan cilexetil provided a significantly greater reductionin sitting systolic (p 5 0.004) and diastolic blood pres-sure (p 5 0.008) than losartan when measured 48 hoursafter the last dose. Moreover, the homogeneity of anti-hypertensive effects was greater after candesartan cilex-etil than losartan based on calculation of the smoothnessindex from ambulatory systolic and diastolic measure-ments during the first 24-hour period after dosing andduring the 12-hour period after the missed dose. Theseresults demonstrate that missing or delaying a dose ofcandesartan cilexetil has less impact on antihyperten-sive efficacy than missing or delaying a dose oflosartan. Q1999 by Excerpta Medica, Inc.

    Am J Cardiol 1999;84:28S34S

    Despite the availability of safe and effective anti-hypertensive medications, blood pressure contin-ues to be poorly controlled in the hypertensive popu-lation.1 Only a minority of patients achieve blood-pressure levels ,140/90 mm Hg as recommended innational and international guidelines for the manage-ment of patients with hypertension.2,3 The Third Na-tional Health and Nutrition Examination Survey(NHANES III) found only about one fourth of nonin-stitutionalized adults with hypertension in the UnitedStates had achieved blood-pressure control.4 Evenamong hypertensive patients being treated with anti-hypertensive medications, less than half had achievedblood pressure control. Similarly, a survey of 73 gen-eral practitioners working at 14 local health officesthroughout Italy found only about one third of hyper-tensive subjects had achieved blood-pressure levels,140/90 mm Hg.5 Notably, results from the secondphase of NHANES III suggest that the percentage ofpatients with controlled blood pressure has remainedstatic in recent years.3

    Several factors are believed to contribute to poorblood-pressure control. It is often difficult to predictwhich patients will respond to a given antihyperten-sive drug class, because the underlying pathophysiol-

    ogy of hypertension is complex.6 However, currentguidelines define an individualized stepwise approachto hypertension management, in which drugs areadded or substituted based on a patients response totreatment.2,3 Nevertheless, many physicians appear re-luctant to aggressively treat hypertension to achieveblood-pressure control.5,7 Some physicians expressconcern about the J-curve hypothesis, which althoughunproved, suggests that excessive blood-pressure low-ering may increase cardiovascular risk. Others fail toaggressively treat hypertension because of concernabout potential drug side effects, and still others ap-pear uncertain about the benefits of antihypertensivetreatment, particularly in patients with mild hyperten-sion. Even in cases where an appropriate treatmentplan has been defined, patients may still not achieveblood-pressure control because they do not follow thephysicians instructions. Many experts believe thatpoor blood-pressure control is largely due to low orunsatisfactory patient compliance.

    PATIENT COMPLIANCEPatient compliance is a complex phenomenon that

    is impacted by numerous factors, including ethnicbackground, educational level, and economic status ofthe patient, and the complexity and side effects asso-ciated with treatment. The educational and economiclevels of patients are related inversely to patient com-pliance and blood-pressure control. In NHANES III,the percentage of hypertensive patients with con-trolled blood pressure was low in both men andwomen and in all ethnic groups, but it was lowest

    From the Clinica Medica, Universita` di MilanoBicocca, Ospedale S.Gerardo, Monza, Milan, Italy.

    Address for reprints: Giuseppe Mancia, MD, University of MilanBicocca, S. Gerardo Hospital, Department of Internal Medicine,Monza, Milan, Italy.

    28S 1999 by Excerpta Medica, Inc. 0002-9149/99/$20.00All rights reserved. PII S0002-9149(99)00731-6

  • among Mexican Americans.4 The impact of drug-induced side effects on patient compliance is oftenunderestimated by physicians, because many patientsfail to inform their physicians that they have discon-tinued treatment due to side effects, some of whichimpact the patients quality of life, such as sexualdysfunction with b blockers. Finally, the complexityof treatment also impacts patient compliance, withpatients being more likely to remain compliant on asimple treatment plan. For example, patient compli-ance is higher with a once-daily antihypertensive med-ication than with an agent that must be taken severaltimes a day.

    Patient compliance is difficult to assess quantita-tively. However, electronic methods, such as the med-ication event monitoring system, have been developedthat record when a drug container is opened andclosed. Although such studies do not prove whetherthe patient has actually ingested the medication, theyprovide an indication of when the patient is likely tohave received treatment. Such studies indicate thatpatient compliance is actually lower than suggested bypill counts or patient self-reports.8,9 Moreover, the useof electronic monitoring suggests that poor patientcompliance is expressed in several different ways.Some patients do not take any pills after a physicianvisit, and only start taking their medication just beforetheir next visit. More often, however, patients takemedications at irregular times and not at the end of thedosing interval as prescribed by the physician. Theymay take the medication earlier than prescribed, butfrequently they take it later than at the prescribedinterval.

    The erratic pattern of patient compliance is illus-trated by results of several studies.10 Moreover, theresults of other studies indicate that a significant pro-portion of patients delay taking medication beyond theprescribed dosing interval.9,11 As a result, antihyper-tensive medications that forgive patients for thisdelay are receiving increasing attention. Such forgiv-ing medications not only control blood pressure dur-ing the dosing interval, but their efficacy extendsbeyond a 24-hour period if the agent is given oncedaily or beyond 12 hours if administered twice daily.

    The effect of delaying treatment beyond the dosinginterval on blood-pressure control has been addressedin so-called missed-dose studies. Blood pressure isrecorded continuously before and after a dose is in-tentionally skipped to determine when blood pressureincreases into the hypertensive range after the misseddose. In one study, ambulatory blood-pressure moni-toring was conducted before and after 6 months oftreatment with the long-acting calcium antagonist,amlodipine.12 Monitoring was conducted for 24 hoursafter the amlodipine dose and then continued for anadditional 24 hours after the next scheduled dose wasskipped. The antihypertensive effect of amlodipinewas maintained throughout the 24-hour period follow-ing the missed dose, which indicated that this agentbelongs to the category of drugs that forgive patients

    for missing or delaying a dose. Other investigatorshave reported similar results. Amlodipine13 and alsonifedipine GITS (Gastrointestinal Therapeutic Sys-tem)14 remained effective after a missed dose, whereasblood-pressure lowering with diltiazem or perindoprilwas diminished.13,15 Missed-dose studies have alsobeen conducted with other antihypertensive drugclasses, and show that some, but not all, members ofeach drug class may forgive patients for missing ordelaying a dose.16,17


    The angiotensin II receptor blockers (ARBs) arethe newest drug class to become available for thetreatment of hypertension. These agents include can-desartan cilexetil, irbesartan, losartan, telmisartan, andvalsartan, all of which are approved for once-dailyadministration. The impact of a missed dose on theantihypertensive effects of candesartan cilexetil andlosartan was evaluated in the CHAMP Study.17 In thisrandomized, double-blind, placebo-controlled trial,patients 2080 years of age with mild-to-moderatehypertension entered a run-in period during whichthey received placebo, and then they were randomizedin a 3 : 3 : 1 ratio to once-daily treatment withcandesartan cilexetil, losartan, or placebo. Candesar-tan cilexetil was administered at a daily dosage of 8mg for the first 4 weeks, and then the dosage was forcetitrated to 16 mg daily for the final 4 weeks of thestudy. Losartan was administered at a daily dosage of50 mg during the first 4-week period and 100 mg dailyduring the final 4-week period. Ambulatory blood-pressure monitoring was conducted for 36 hours atbaseline, and after 4 and 8 weeks of treatment.

    During the first 24-hour period after dosing, bothcandesartan cilexetil and losartan lowered ambulatorysystolic and diastolic blood pressure relative to base-line levels (Figure 1). At the week 8 assessment,r


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