Immediate-release oxybutynin versus tolterodine in detrusor overactivity: a population analysis

We evaluated adherence to treatment with immediate-release (IR) oxybutynin (515 patients) and tolterodine (505 patients) for detrusor overactivity through retrospective analysis of a pharmacy claims database. Outcomes included percentage of patients continuing therapy for 6 months, medication possession ratios, and time to discontinuation of therapy. The proportion of patients continuing therapy for 6 months was statistically superior for tolterodine (32%) compared with IR oxybutynin (22%, p<0.001). Medication possession ratios were also superior for patients in the tolterodine group (medians 0.83 and 0.64, ranges 0.11-1.15 and 0.07-1.13, respectively, p<0.001). Oxybutynin was discontinued significantly earlier (mean 45 days) than tolterodine (mean 59 days, p<0.001) and was switched to another therapy more commonly than tolterodine (19% and 14%, respectively). Tolterodine was favored over oxybutynin for several measurements of patient adherence. However, less than one-third of patients continued therapy with either agent for 6 months. The clinical relevance of these differences is unknown.

Patient self-reporting of compliance does not correspond with electronic monitoring: an evaluation using isosorbide dinitrate as a model drug

STUDY OBJECTIVE

To assess the accuracy of patient-kept diaries relative to electronic monitoring of compliance with isosorbide dinitrate prescribed 3 times/day for ischemic heart disease.

DESIGN

Unblinded, prospective, three-phase study.

METHODS

Patients with coronary artery disease prescribed isosorbide dinitrate 3 times/day were asked to record the time of administration of each dose in a pocket diary while being monitored for compliance with a computerized Medication-Event Monitoring System (MEMS-4) vial that electronically recorded the date and time the vial was opened.

RESULTS

Sixty-eight stable outpatients with documented coronary artery disease who were prescribed isosorbide dinitrate 3 times/day were evaluated. Based on a prospectively chosen definition including a nitrate-free period, the mean (+/-SD) overall compliance rates were 71% (+/-30) versus 55% (+/-32) for the patient-kept diaries and the MEMS vials respectively (p = 0.001). The concordance between patient-kept diaries and MEMS data indicate that 67% of patients overestimate their compliance when using a self-recording tool. An average of 30% of diary entries were in error compared with the MEMS vial recordings.

CONCLUSIONS

Patient-kept diaries statistically overestimate actual compliance relative to that determined by MEMS devices. Given the prevalence of the use of diaries as the predominant tool on which researchers depend to document compliance with study drugs, our findings suggest that this practice should be reevaluated specifically when the time of the dose and documentation of administration are critical to qualifying the outcome of drug therapy. Such is the case with isosorbide dinitrate use in patients with ischemic heart disease. Furthermore, the overall poor compliance documented in this study suggests that the utility of isosorbide dinitrate prescribed 3 times/day be reevaluated as a clinically effective antianginal drug.

Chronopharmacologic considerations when treating the patient with hypertension: a review

Recognition of the existence of circadian variation in exacerbation of cardiovascular disease may have relevance to clinical use of cardioactive agents. Physiologic rational for the chronobiology of cardiac disease exists and can provide a basis on which to examine the efficacy of agents to manage cardiac disease. The use of 24-hour ambulatory blood pressure monitoring (ABPM) devices have advanced our ability to describe the interplay of chronobiologic rhythms and pharmacodynamic response to antihypertensive medications. This review summarizes the studies evaluating the use of various antihypertensive medications in the context of using 24-hour blood pressure monitoring devices. The studies are described in an attempt to increase awareness of chronobiology and potential implications of designing chronotherapeutic regimens.

Predominance of slow acetylators of N-acetyltransferase in a Hmong population residing in the United States

Pharmacogenetics can be an important determinant of pharmacologic response. To learn more about interpopulation differences in drug metabolism between ethnically diverse populations of subjects cared for by an International Clinic, a study was conducted to describe the prevalence of fast or slow acetylators of N-acetyltransferase (NAT2) in a population of Hmong residing in Minnesota. Ninety-eight healthy Hmong refugees from Laos volunteered to take caffeine as an oral probe drug to establish acetylator phenotype. Participants were classified as either rapid or slow acetylators based on the urinary molar ratio of select metabolites of caffeine. Assignment of phenotype was based on results from analysis of urine collected subsequent to ingestion of caffeine. The ratio of 5-acetylamino-6-formylamino-3-methyluracil (AFMU) to the combined products of the 7-demethylation pathway of paraxanthine (AFMU, 1-methylxanthine (1X), and 1-methylurate (1U)] formed the basis for this determination. A probit plot of the data collected in our subjects qualified a metabolic ratio of 0.34 as an acceptable cut point for phenotype assignment. Participants with an AFMU/(AFMU + 1X + 1U) ratio of < 0.34 were classified as slow acetylators and all others as rapid acetylators. Analysis of the data suggested a bimodal distribution with an excess (74.5%) of slow acetylators in the population. The predominance of slow acetylators found in the Hmong contrast with the prevalence of slow acetylators seen in other ethnic groups. These findings may have important clinical implications given the large number of Hmong treated each year in our International Clinic and the increasing use of medications metabolized by NAT2 in this population.

Magnitude and nature of noncompliance with treatment using isosorbide dinitrate in patients with ischemic heart disease

Isosorbide dinitrate is one of the most commonly prescribed medications for the treatment of ischemic heart disease. It has been demonstrated to be ineffective relative to placebo when taken inappropriately. This study objectively documents the magnitude and nature of compliance in 68 ambulatory patients who were prescribed isosorbide dinitrate three times a day. Each patient received a 9-week supply of medication in a vial equipped with a computerized monitor (MEMS-4 cap; APREX Corporation, Fremont, CA) and were informed as to the purpose of the study. Of the patients, 74% were classified into the low and 16% into the high compliance category, defined as compliant < 70% and > or = 85% of study days, respectively. The mean (+/- SD) percent days in which isosorbide dinitrate was taken three times was 66% (+/- 29), and the mean number of days in which it was taken three times with a 10-hour "nitrate free period" was 53% (+/- 31). It is concluded that the magnitude of noncompliance in patients prescribed isosorbide dinitrate three times daily is substantial (74%). The nature of this noncompliance is often due to failure to observe a 10- to 12-hour nitrate free period. Given the need to take isosorbide dinitrate appropriately and given the demonstrated magnitude of noncompliance, physicians should take these factors into consideration when selecting this agent for the management of coronary artery disease relative to other pharmacologic options.