Pharmacodynamics of variable patient compliance: implications for pharmaceutical value

Patient-Led Urate Self-Monitoring to Improve Clinical Outcomes in People With Gout: A Feasibility Study

OBJECTIVE

Self-monitored point-of-care urate-measuring devices are an underexplored strategy to improve adherence to urate-lowering therapy and clinical outcomes in gout. This study observed patient-led urate self-monitoring practice and assessed its influence on allopurinol adherence, urate control, and health-related quality of life.

METHODS

People with gout (n = 31) and prescribed allopurinol self-monitored their urate concentrations (HumaSens2.0plus) at baseline and thereafter monthly for 12 months (3 months per quarter). Adherence to allopurinol was measured using medication event monitoring technology (Medication Event Monitoring System cap). Time spent below the target urate concentration (<0.36 mmol/L) was determined. Health-related quality of life was measured using a survey (EuroQoL EQ-5D-5L). Gout flares were recorded. Two-tailed Spearman correlation and the Wilcoxon matched-pairs signed-rank test (P < 0.05) were used for statistical comparisons.

RESULTS

Most participants were male (94%) and had urate concentrations below the target (74%) at baseline. Overall, seven participants demonstrated repeated periods of "missed doses" (two or fewer allopurinol doses missed consecutively) and "drug holidays" (three or more missed doses). Most participants (94%) persisted with allopurinol. Time spent within the target urate concentration increased 1.3-fold (from 79% to 100%; P = 0.346), and the incidence of gout flares decreased 1.6-fold (from 8 to 5; P = 0.25) in the final quarter compared to that in the first quarter of the study. Health-related quality of life was reduced for participants reporting at least one gout flare (median utility values 0.9309 vs 0.9563, P = 0.04).

CONCLUSION

Patient-led urate self-monitoring may support the maintenance of allopurinol adherence and improve urate control, thus reducing the incidence of gout flares. Further research on patient-led urate self-monitoring in a randomized controlled study is warranted.

Investigating Levothyroxine Use and Its Association with Thyroid Health in Patients with Hypothyroidism: A Community Pharmacy Study

Background: To gain maximum therapeutic effect while minimizing side effects, it is imperative for patients with hypothyroidism to use their levothyroxine (LT4) correctly, such as adhering to the prescribed regimen. Little is currently known about how patients actually use LT4 in real life. We investigated the use of LT4, as well as the thyroid health (thyrotropin [TSH] and health-related quality of life [HR-QoL]), and evaluated if proper LT4 use is associated with better thyroid health. Methods: A cross-sectional observational study was conducted in a Belgian community sample of adults using LT4 for hypothyroidism since ≥2 years. Participants completed a self-administered questionnaire on patient characteristics, self-reported adherence to LT4, timing of intake, and co-medication. They also completed the thyroid-specific patient-reported outcome (ThyPRO-39) questionnaire, measuring the HR-QoL. Pharmacy dispensing data were used to calculate the medication possession ratio (MPR). Results: We included 856 participants (mean age 61.4 ± 14.3 years, 86% [740/856] females). Approximately one in four participants (138/563) had out-of-range TSH levels. Generally, ThyPRO-39 scores were in the lower part of the range (indicating better HR-QoL), with the scales "emotional susceptibility" and "tiredness" showing the worst scores. Approximately 28% (178/632) of the participants were classified as non-adherent (MPR <80%), corresponding to at least 73 cumulative days per year without LT4 intake. Twenty-five percent (212/854) of participants self-reported non-adherence, with unintentional non-adherence (forgetfulness) most frequently reported (21.9%, 187/854). Only 39% (329/836) of participants complied with the recommendation of ingesting LT4 ≥ 30 minutes before eating. Additionally, 7% (58/856) of participants concurrently used molecules that bind to LT4, without applying the recommended dosing interval. There was no significant correlation between LT4 usage (adherence, timing of intake, and interaction with complex forming drugs) and TSH or HR-QoL. Conclusions: We found that many participants with hypothyroidism did not use their LT4 as effectively as possible, particularly with respect to timing of administration. However, the participants' HR-QoL seemed largely satisfactory, and there was no significant correlation between correctly using LT4 and thyroid health.

Medicine shortages: impact behind numbers

INTRODUCTION

Current research to assess the impact that medicine shortages have on patients is limited to general aspects, such as the prevalence of shortages and product characteristics. The aim of this study is to assess the overall impact that medicine shortages have on economic, clinical, and humanistic outcomes.

METHODS

A cohort of all known products in shortage in the Netherlands between 2012 and 2015 were characterized by their route of administration, anatomical therapeutic chemical class, and whether they were originator or generic products. A representative sample of 324 shortages (18% of all shortages) was rated as having low, medium, or high impact on the five elements that determine the impact of shortages on patients: availability of an alternative product, underlying disease, susceptibility of the patient, costs (for patients and society at large), and number of patients affected. Ratings were converted into numerical scores per element and multiplied to obtain an overall impact score.

RESULTS

Two elements were most frequently rated as having a high impact: disease (29%) and costs (20%). Nearly half of the shortages (47%) rated high on at least one element, while nearly 10% rated high on multiple elements. Thirty percent of the shortages rated high on direct impact, which is represented by these elements: alternative product and disease. An additional 17% of the shortages rated high on indirect impact, which is represented by these elements: costs, susceptibility, and number of patients. High impact scores could not significantly be attributed to characteristics of the products in shortage.

CONCLUSIONS

An assessment of the medicine shortages' impact using a framework based on economic, clinical, and economic outcomes showed that all three outcomes affect the overall impact that medicine shortages have on patients.

Impact of medicine shortages on patients - a framework and application in the Netherlands

Background

Medicine shortages are often described in plain numbers, suggesting all shortages have a uniform impact. However, some shortages have a direct and serious effect on patients and need a prompt reaction from stakeholders. This study aims to create a broad framework to assess the impact of a shortage.

Method

We identified high impact shortages and selected exemplary shortages which we considered our learning cases. From five learning cases, we identified elements that had a potentially profound impact on one or more of these cases. We tested data saturation on the elements with another five test cases. Based on these elements, we created a framework to assess impact of shortages on patients and presented practical examples how to rate these different elements. Subsequently, we visualised the impact of these five learning cases on patients in radar charts.

Results

The five elements which we identified as potentially having a large impact were 1) alternative product, 2) disease, 3) susceptibility, 4) costs and 5) number of patients affected. The five learning cases rated high on different elements, leading to diverse and sometimes even opposite patterns of impact.

Conclusion

We created a framework for assessing the impact of a medicine shortage on patients by means of five key elements. By rating these elements, an indication of the impact can be obtained.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-022-08765-x.

Regularity of self-reported daily dosage of mood stabilizers and antipsychotics in patients with bipolar disorder

BACKGROUND

Polypharmacy is often prescribed for bipolar disorder, yet medication non-adherence remains a serious problem. This study investigated the regularity in the daily dosage taken of mood stabilizers and second generation antipsychotics.

METHODS

Daily self-reported data on medications taken and mood were available from 241 patients with a diagnosis of bipolar disorder who received treatment as usual. Patients who took the same mood stabilizer or second generation antipsychotic for ≥ 100 days were included. Approximate entropy was used to determine serial regularity in daily dosage taken. Generalized estimating equations were used to estimate if demographic or clinical variables were associated with regularity.

RESULTS

There were 422 analysis periods available from the 241 patients. Patients took drugs on 84.4% of days. Considerable irregularity was found, mostly due to single-day omissions and dosage changes. Drug holidays (missing 3 or more consecutive days) were found in 35.8% of the analysis periods. Irregularity was associated with an increasing total number of psychotropic drugs taken (p = 0.009), the pill burden (p = 0.026), and the percent of days depressed (p = 0.049).

CONCLUSION

Despite low missing percent of days, daily drug dosage may be irregular primarily due to single day omissions and dosage changes. Drug holidays are common. Physicians should expect to see partial adherence in clinical practice, especially with complex drug regimens. Daily dosage irregularity may impact the continuity of drug action, contribute to individual variation in treatment response, and needs further study.

A framework for quantifying the influence of adherence and dose individualization

A failure to accommodate for a patient's imperfect adherence may result in therapeutic failure. Similarly, failure to accommodate a patient's individual needs via dose individualization may also result in poor patient outcomes. The property of a drug that signifies the likelihood of therapeutic success to imperfect adherence is termed "forgiveness." We introduce an extension to this concept as: (1) a priori forgiveness (forgiveness when dose individualization is not considered) and (2) a posteriori forgiveness (forgiveness when considering dose individualization). We illustrate cases when adherence is of primary importance and in which dose individualization is of primary importance. The concept of a priori forgiveness and a posteriori forgiveness provides a quantitative measure that allows the influence of adherence to be disentangled from dose individualization and could be used to provide clear guidelines about the relative importance of each in clinical practice.

Quantification of the Forgiveness of Drugs to Imperfect Adherence

The circumstance of how sensitive therapeutic success is under imperfect adherence is driven by the property known as forgiveness. To date, no studies have considered variability in the pharmacokinetic-pharmacodynamic process in conjunction with imperfect adherence patterns in order to develop a comparative criterion to determine the forgiveness of a drug. In this study, we have proposed a criterion to quantify forgiveness; illustrated the criterion for a theoretical example and evaluated the forgiveness of a motivating example, namely warfarin. A forgiveness criterion, relative forgiveness, is defined as the number of times more likely that a target is successfully attained under perfect adherence compared to imperfect adherence; or when comparing two drugs under a standard setting of imperfect adherence. The relative forgiveness criterion may have important implications for both drug development and clinical practice since the choice of drug can account for the likely influence of its forgiveness.

Antidepressant dosage taken by patients with bipolar disorder: factors associated with irregularity

BACKGROUND

This study analyzed regularity in the daily dosage of antidepressants taken by patients with bipolar disorder and identified the factors associated with irregularity.

METHODS

Daily self-reported medication dosage taken and mood ratings were available from 144 patients who received treatment as usual. All 144 patients took the same antidepressant for at least 100 days. One hundred eleven of these patients were also taking a mood stabilizer. Approximate entropy (ApEn) was used to measure serial regularity in daily dosage. Regularity is the tendency that values within a time series remain the same on incremental comparisons. Drug holidays (missing three or more consecutive days) were also determined. Generalized estimating equations (GEE) were used to estimate if any demographic or clinical variables were associated with regularity.

RESULTS

Although the mean percent of days missing doses was only 18.6%, there was a wide range of regularity in the daily antidepressant dosage. Drug holidays were common, occurring in 41% of the analyses. Factors significantly associated with irregularity were as follows: total number of psychotropic medications (p = 0.005), pill burden (p = 0.005), and depression (p = 0.015). Neither the percent of days missing doses nor the drug holidays were associated with any demographic or clinical factors. For patients taking both antidepressants and mood stabilizers, there was no significant difference in regularity in daily dosage between these drugs.

DISCUSSION

There can be considerable irregularity in daily dosage despite a low percent of days missing doses. Medication regimen complexity and depressed mood are associated with increased irregularity. Daily regularity in drug dosage may be more dependent on the individual than on the specific drug. Research on the clinical impact of irregularity in daily dosage of antidepressants is needed.

Sustained blood pressure-lowering effect of aliskiren compared with telmisartan after a single missed dose

Poor adherence to antihypertensive drug treatment is common and is often associated with marked prolongations of the dosing interval. Hence, selecting a treatment that has the potential to provide a sustained blood pressure (BP)-lowering effect is important. The objective of this analysis is to compare the sustained efficacy of aliskiren with telmisartan after a single missed dose. This is part of a 12-week double-blind study conducted in patients with mild to moderate hypertension randomized to once-daily aliskiren 150 mg or telmisartan 40 mg for 2 weeks, force-titrated to double the doses for 10 weeks, followed by placebo for 1 week. The changes in BP from the end of active treatment (EOA) to 48 hours after treatment withdrawal (day 2) were analyzed. Demographic and baseline characteristics were comparable between the treatment groups. Aliskiren continued to show significantly greater reductions in mean sitting systolic BP (-0.7 vs +1.3 mm Hg; P<.05), 24-hour mean ambulatory systolic BP (-3.6 vs +2.6 mm Hg; P<.01), and 24-hour mean ambulatory diastolic BP (-3.7 vs +0.4 mm Hg; P<.01) compared with telmisartan from EOA to day 2, despite the similar BP reductions from randomization to EOA. In conclusion, aliskiren sustained the BP-lowering efficacy better than telmisartan after a single missed dose.

[Compliance enhancement in drug therapy : opportunities and limitations]

In the execution of their pharmacotherapy, many patients deviate from the prescribed treatment regimen. Reasons for noncompliance can be diverse and range from forgetfulness of the patient to attributes of the health care system. Besides increased health care costs, poor compliance causes both an endangerment to the patient and poor health outcomes. Therefore, it is crucial that compliance enhancement receives high priority. In the beginning of this process, noncompliance must be detected in daily practice. Moreover, various methods can provide valuable information about medication-taking behavior, time patterns, and reasons for noncompliance. Based on this assessment, appropriate measures to enhance compliance can be taken. In this article, the opportunities and limitations of compliance enhancement are discussed.

Adherence to medications: insights arising from studies on the unreliable link between prescribed and actual drug dosing histories

Satisfactory adherence to aptly prescribed medications is essential for good outcomes of patient care and reliable evaluation of competing modes of drug treatment. The measure of satisfactory adherence is a dosing history that includes timely initiation of dosing plus punctual and persistent execution of the dosing regimen throughout the specified duration of treatment. Standardized terminology for initiation, execution, and persistence of drug dosing is essential for clarity of communication and scientific progress. Electronic methods for compiling drug dosing histories are now the recognized standard for quantifying adherence, the parameters of which support model-based, continuous projections of drug actions and concentrations in plasma that are confirmable by intermittent, direct measurements at single time points. The frequency of inadequate adherence is usually underestimated by pre-electronic methods and thus is clinically unrecognized as a frequent cause of failed treatment or underestimated effectiveness. Intermittent lapses in dosing are potential sources of toxicity through hazardous rebound effects or recurrent first-dose effects.

Effects of daily adherence to antihypertensive medication on blood pressure control

Clinicians are often uncertain about how to manage elevated blood pressure (BP) when a patient reports that he/she has recently missed several doses of antihypertensive medications. While we know that better adherence can improve BP during several months, the magnitude of this relationship in the short term is poorly understood. The authors examined this issue using a group of patients who monitored adherence using a Medication Events Monitoring System (MEMS) cap and had BP measurements in the course of routine clinical practice. BP readings were compared following 7 days of excellent adherence (100%) or poor adherence (< 60%), omitting BP values following intermediate adherence. Using several different methods, BP following 7 days of excellent adherence was between 12/7 mm Hg and 15/8 mm Hg lower than after 7 days of poor adherence. Clinicians can use this effect size to calibrate their impressions of what the BP might have been with improved adherence.

Impact of prolonged antihypertensive duration of action on predicted clinical outcomes in imperfectly adherent patients: comparison of aliskiren, irbesartan and ramipril

BACKGROUND

Most patients miss occasional doses of antihypertensives. The use of 'forgiving' drugs (i.e. drugs with duration of action longer than the 24-h dosing interval) may allow an adequate blood pressure (BP) reduction to be maintained despite missed doses.

AIM

To quantify the effects of adherence level and duration of action on estimated mean systolic BP (SBP) reduction and cardiovascular disease (CVD) risk.

METHOD

For 1250 patients, we simulated 256-day dosing histories with realistically distributed drug holidays based on a study of electronically monitored dosing records. Adherence was set to the desired level by altering the proportion of doses missed. Mean office SBP-lowering effect (aliskiren 300 mg, -14.1 mmHg; irbesartan 300 mg, -13.3; ramipril 10 mg, -10.1 mmHg) and the rate of SBP increase after stopping treatment (off-rate; aliskiren, 1.0 mmHg/day; irbesartan, 3.6 mmHg/day; ramipril, 4.0 mmHg/day) were taken from the results of a randomised, double-blind trial. SBP was averaged over time and patient to estimate mean reductions in SBP and 10-year CVD risk (Framingham risk equation, baseline absolute 10-year CVD risk: 27%).

RESULTS

Predicted reductions in SBP and CVD risk with aliskiren were larger and less affected by imperfect adherence than the reductions with irbesartan or ramipril. For aliskiren, reducing adherence from 90% to 60% led to a predicted rise in SBP of 1.0 mmHg and three additional CVD events per 1000 treated patients; larger predicted differences were observed for irbesartan (2.5 mmHg; 7.5 events/1000 treated patients) and ramipril (2.2 mmHg; 6.7 events/1000 treated patients).

CONCLUSION

To offset the effects of imperfect adherence, a common challenge with antihypertensives, for better BP management it may be prudent to prescribe 'forgiving' drugs.

Effects on blood pressure and cardiovascular risk of variations in patients' adherence to prescribed antihypertensive drugs: role of duration of drug action

AIM

To determine the effects of imperfect adherence (i.e. occasionally missing prescribed doses), and the influence of rate of loss of antihypertensive effect during treatment interruption, on the predicted clinical effectiveness of antihypertensive drugs in reducing mean systolic blood pressure (SBP) and cardiovascular disease (CVD) risk.

METHOD

The effects of imperfect adherence to antihypertensive treatment regimens were estimated using published patterns of missed doses, and taking into account the rate of loss of antihypertensive effect when doses are missed (loss of BP reduction in mmHg/day; the off-rate), which varies between drugs. Outcome measures were the predicted mean SBP reduction and CVD risk, determined from the Framingham Risk Equation for CVD.

RESULTS

In patients taking 75% of prescribed doses (typical of clinical practice), only long-acting drugs with an off-rate of ∼1 mmHg/day were predicted to maintain almost the full mean SBP-lowering effect throughout the modelled period. In such patients, using shorter-acting drugs (e.g. an off-rate of ∼5-6 mmHg/day) was predicted to lead to a clinically relevant loss of mean SBP reduction of > 2 mmHg. This change also influenced the predicted CVD risk reduction; in patients with a baseline 10-year CVD risk of 27.0% and who were taking 75% of prescribed doses, a difference in off-rate from 1 to 5 mmHg/day led to a predicted 0.5% absolute increase in 10-year CVD risk.

CONCLUSIONS

In patients who occasionally miss doses of antihypertensives, modest differences in the rate of loss of antihypertensive effect following treatment interruption may have a clinically relevant impact on SBP reduction and CVD risk. While clinicians must make every effort to counsel and encourage each of their patients to adhere to their prescribed medication, it may also be prudent to prescribe drugs with a low off-rate to mitigate the potential consequences of missing doses.

Understanding forgiveness: minding and mining the gaps between pharmacokinetics and therapeutics

The usual objective during long-term pharmacotherapy is, in large part, to maintain continuity of action of the prescribed drug(s). Continuity of action arises from the continuity of execution of a prescribed dosing regimen that is pharmacologically sound in dose quantity and interval between successive doses. Interruptions in dosing can interrupt drug action, but the consequences vary according to length of interruption, drug, drug formulation, length of the patient's prior exposure to the drug, and the disease being treated.

Compliance assessment of ambulatory Alzheimer patients to aid therapeutic decisions by healthcare professionals

Background

Compliance represents a major determinant for the effectiveness of pharmacotherapy. Compliance reports summarising electronically compiled compliance data qualify healthcare needs and can be utilised as part of a compliance enhancing intervention. Nevertheless, evidence-based information on a sufficient level of compliance is scarce complicating the interpretation of compliance reports. The purpose of our pilot study was to determine the compliance of ambulatory Alzheimer patients to antidementia drugs under routine therapeutic use using electronic monitoring. In addition, the forgiveness of donepezil (i.e. its ability to sustain adequate pharmacological response despite suboptimal compliance) was characterised and evidence-based guidance for the interpretation of compliance reports was intended to be developed.

Methods

We determined the compliance of four different antidementia drugs by electronic monitoring in 31 patients over six months. All patients were recruited from the gerontopsychiatric clinic of a university hospital as part of a pilot study. The so called medication event monitoring system (MEMS) was employed, consisting of a vial with a microprocessor in the lid which records the time (date, hour, minute) of every opening. Daily compliance served as primary outcome measure, defined as percentage of days with correctly administered doses of medication. In addition, pharmacokinetics and pharmacodynamics of donepezil were simulated to systematically assess therapeutic undersupply also incorporating study compliance patterns. Statistical analyses were performed with SPSS and Microsoft Excel.

Results

Median daily compliance was 94% (range 48%-99%). Ten patients (32%) were non-compliant at least for one month. One-sixth of patients taking donepezil displayed periods of therapeutic undersupply. For 10 mg and 5 mg donepezil once-daily dosing, the estimated forgiveness of donepezil was 80% and 90% daily compliance or two and one dosage omissions at steady state, respectively. Based on the simulation findings we developed rules for the evidence-based interpretation of donepezil compliance reports.

Conclusions

Compliance in ambulatory Alzheimer patients was for the first time assessed under routine conditions using electronic monitoring: On average compliance was relatively high but variable between patients. The approach of pharmacokinetic/pharmacodynamic in silico simulations was suitable to characterise the forgiveness of donepezil suggesting evidence-based recommendations for the interpretation of compliance reports.

The association between concurrent psychotropic medications and self-reported adherence with taking a mood stabilizer in bipolar disorder

OBJECTIVE

Multiple psychotropic medications are routinely prescribed to treat bipolar disorder, creating complex medication regimens. This study investigated whether the daily number of psychotropic medications or the daily number of pills were associated with self-reported adherence with taking a mood stabilizer.

METHODS

Patients self-reported their mood and medications taken daily for about 6 months. Adherence was defined as taking at least one pill of any mood stabilizer daily. Univariate general linear models (GLMs) were used to estimate if adherence was associated with the number of daily medications and the number of pills, controlling for age. The association between mean daily dosage of mood stabilizer and adherence was also estimated using a GLM.

RESULTS

Three hundred and twelve patients (mean age 38.4 +/- 10.9 years) returned 58,106 days of data and took a mean of 3.1 +/- 1.6 psychotropic medications daily (7.0 +/- 4.2 pills). No significant association was found between either the daily number of medications or the daily number of pills and adherence. For most mood stabilizers, patients with lower adherence took a significantly smaller mean daily dosage.

CONCLUSIONS

The number of concurrent psychotropic medications may not be associated with adherence in bipolar disorder. Patients with lower adherence may be taking smaller dosages of mood stabilizers.

Measurement of adherence, drug concentrations and the effectiveness of artemether-lumefantrine, chlorproguanil-dapsone or sulphadoxine-pyrimethamine in the treatment of uncomplicated malaria in Malawi

Background

Sulphadoxine-pyrimethamine (SP) is the only single dose therapy for uncomplicated malaria, but there is widespread resistance. At the time of this study, artemether-lumefantrine (AL) and chlorproguanil-dapsone (CPD), both multi-dose regimes, were considered possible alternatives to SP in Malawi. The aim of this study was to investigate the impact of poor adherence on the effectiveness of AL and CPD.

Methods

Children ≥12 months and adults with uncomplicated malaria were randomized to receive AL, CPD or SP. Adherence was measured using a questionnaire and electronic monitoring devices, MEMS™, pill bottles that recorded the date and time of opening. Day-7 plasma dapsone or lumefantrine concentrations were measured to examine their relationship with adherence and clinical response.

Results

841 patients were recruited. The day-28 adequate clinical and parasitological response (ACPR) rates, using intention to treat analysis (missing data treated as failure), were AL 85.2%, CPD 63.7% and SP 50%. ACPR rates for AL were higher than CPD or SP on days 28 and 42 (p ≤ 0.002 for all comparisons). CPD was more effective than SP on day-28 (p = 0.01), but not day-42.

Very high adherence was reported using the questionnaire, 100% for AL treated patients and 99.2% for the CPD group. Only three CPD participants admitted missing any doses. 164/181 (90.6%) of CPD treated patients took all their doses out of the MEMS™ container and they were more likely to have a day-28 ACPR than those who did not take all their medication out of the container, p = 0.024. Only 7/87 (8%) AL treated patients did not take all of their doses out of their MEMS™ container and none had treatment failure.

Median day-7 dapsone concentrations were higher in CPD treated patients with ACPR than in treatment failures, p = 0.012. There were no differences in day-7 dapsone or lumefantrine concentrations between those who took all their doses from the MEMS™ container and those who did not. A day-7 lumefantrine concentration reported to be predictive of AL treatment failure in Thailand was not useful in this population; only one of 16 participants with a concentration below this threshold (175 ng/ml) had treatment failure.

Conclusion

This study provides reassurance of the effectiveness of AL, even with unsupervised dosing, as it is rolled out across sub-Saharan Africa. Self-reported adherence appears to be an unreliable measure of adherence in this population.

Intensifying therapy for hypertension despite suboptimal adherence

More intensive management can improve control blood pressure (BP) in hypertensive patients. However, many would posit that treatment intensification (TI) is not beneficial in the face of suboptimal adherence. We investigated whether the effect of TI on BP varies by adherence. We enrolled 819 patients with hypertension, managed in primary care at an academically-affiliated inner-city hospital. We used the following formula to characterize TI: (visits with a medication change-visits with elevated BP)/total visits. Adherence was characterized using electronic monitoring devices ("MEMS caps"). Patients who returned their MEMS caps (671) were divided into quartiles of adherence, whereas patients who did not return their MEMS caps (148) had "missing" adherence. We examined the relationship between TI and the final systolic blood pressure (SBP), controlling for patient-level covariates. In the entire sample, each additional therapy increase per 10 visits predicted a 2.0 mm Hg decrease in final SBP (P<0.001). After stratifying by adherence, in the "best" adherence quartile each therapy increase predicted a 2.1-mm Hg decrease in final SBP, followed by 1.8 for the "next-best" adherence quartile, 2.3 in the third quartile, and 2.4 in the "worst" adherence quartile. The effect size for patients with "missing" adherence was 1.6 mm Hg. The differences between the group with "best" adherence and the other 4 groups were not statistically significant. In this observational study, treatment intensification was associated with similar BP improvement regardless of the patient's level of adherence. A randomized trial could further examine optimal management of patients with suboptimal adherence.

A probabilistic approach for the evaluation of pharmacological effect induced by patient irregular drug intake

Fine individual drug intake data, generally collected by electronic monitoring devices, reveal that individual marked random patterns are likely to persist through long therapeutic periods. This work aims to establish the relationship between irregularity in drug intake and its potential impact on therapeutic outcomes, which will also serve as a basis for more objective interventions. First we proposed a direct way to extract the necessary information representing the patient drug intake history. To provide a fair evaluation of the pharmacological performance, we revisited several classical pharmacological indices and proposed new ones in the stochastic context of patient's drug intake irregularity. To illustrate our procedure, we have considered two cases of HIV treatment using a combination of lopinavir/ritonavir (Kaletra@) for once daily and twice daily regimens. We have quantified the impact on therapeutic effect of various characteristics in dosing histories, namely missing doses and deviations from nominal times. Using our newly defined pharmacological indices, we clearly showed the ability of our probabilistic approach in measuring the impact of noncompliance. As a direct fallout, we have discussed strategies to attenuate the impact of noncompliance through an optimal design of dosing regimen.

Adherence to prescribed antihypertensive drug treatments: longitudinal study of electronically compiled dosing histories

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 1989-2006.

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), beta 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.

Estimation of the impact of noncompliance on pharmacokinetics: an analysis of the influence of dosing regimens

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Patient compliance is better with formulations that require less frequent dosing than with formulations that require more frequent dosing. Intramuscular risperidone and long-acting oxybutynin are two examples of medicines reformulated for less frequent dosing. However, it is not clear whether better compliance with less frequent dosing regimens translates to improved therapeutic outcome.

WHAT THIS STUDY ADDS

At equivalent daily doses and typical patterns of compliance, fortnightly intramuscular depot administrations of risperidone provide better pharmacokinetic coverage than once-daily oral dosing. Once-daily dosing of oxybutynin is no better at maintaining pharmacokinetic exposure than twice-daily dosing at half strength. The use of simulated compliance data as input to pharmacokinetic models is useful to assess the impact of noncompliance on internal drug exposure.

AIMS

To determine whether, for oxybutynin and risperidone, drug exposure is better with less frequent dosing regimens than with regimens that require more frequent dosing.

METHODS

Pharmacokinetic models of oxybutynin (5 mg twice-daily and 10 mg once-daily) and risperidone (2 mg once-daily orally and 25 mg fortnightly intramuscular injection) were developed. Simulations of multiple doses were performed by use of stochastic models of dose-taking compliance and clinic visit attendance.

RESULTS

At therapeutic concentrations and with typical patterns of noncompliance, intramuscular injections of risperidone resulted in a 41% (SD 12%) greater pharmacokinetic coverage than the oral dose, 76% (SD 10%) vs. 35% (SD 7%). No discernable differences were evident between once- and twice-daily formulations of oxybutynin, 29.2% (SD 10%) vs. 29.0% (SD 13%).

CONCLUSIONS

For equivalent doses for each drug, the longer acting preparation of risperidone, but not oxybutynin, is pharmacokinetically more forgiving of noncompliance than the shorter acting counterparts. Further analysis is required to confirm whether these observations are valid clinically.

Extended-release formulations for the treatment of epilepsy

This review analyses the concept of extended-release (ER) formulations in epilepsy and evaluates ER formulations of carbamazepine, valproic acid and a modified-release (MR) formulation of oxcarbazepine. ER formulations are usually designed to reduce dose frequency and maintain relatively constant or flat plasma drug concentration. It is questionable whether flat plasma concentrations of an antiepileptic drug (AED) improve antiepileptic efficacy compared with fluctuating plasma concentrations. More certainly, they minimise concentration-related adverse effects, and the dosing flexibility and consistency of plasma concentrations may simplify the management of antiepileptic drug therapy. Neurologists would like ER formulations that can be administered once- and/or twice-daily to tailor therapy for the individual patient; however, switching dosage schedules from multiple dosages per day to once daily, although more convenient, will not generally improve therapeutic coverage (maintenance of effective drug concentration in biological fluids and tissue). Pharmacokinetically, the impact of a missed dose is greater the larger the dose and the less frequent the administration. Therefore, the risk of breakthrough seizure is higher during AED once-daily administration than twice-daily administration. Consequently, the increased compliance observed with fewer dosages per day should be weighed against the impact or forgiveness of omitted dose(s) and the shorter 'forgiveness' period associated with once-daily administration. Currently, the trend is to treat patients with epilepsy with ER formulations because of the better compliance, convenience and flat plasma concentration versus time curve. Thus, it seems that the term 'flatter is better' for AED plasma profiles has precipitated in the last 10-15 years among neurologists and epilepsy caregivers, and is being promoted by marketing forces of pharmaceutical companies. Data from the literature support the trend to treat epileptic patients with twice-daily administration of the existing ER formulations of valproic acid and carbamazepine, and oxcarbazepine-MR; however, the author of this article is not convinced that these ER formulations can guarantee a complete therapeutic coverage throughout the 24-hour dosing interval following once-daily administration. Epilepsy is a single-episode disease, and the convenience and possible better compliance associated with once-daily administration must be weighed against the shorter 'forgiveness' period and possible higher risk of breakthrough seizure due to sub-therapeutic plasma levels and/or omitted doses. Data suggest just a small difference in compliance between once- and twice-daily administration, with no significant difference in efficacy. Therefore, the increased compliance following once-daily administration may be counter-productive in minimising the occurrence of sub-therapeutic drug concentrations. Weighing up the advantages and disadvantages for once- versus twice-daily administration of ER formulations in epilepsy leads to a conclusion in favour of twice-daily administration.

Adherence in glaucoma: objective measurements of once-daily and adjunctive medication use

PURPOSE

To determine with electronic monitoring an objective measurement of adherence in two populations of subjects: those using once-daily prostaglandin analogs as sole ocular hypotensive therapy (one-drug group) and those requiring an adjunctive medicine to the prostaglandin analog (two-drug group).

DESIGN

Single-site, open-label, nonrandomized, parallel design of 60 days.

METHODS

Sixty-two consecutive adult subjects with a diagnosis of open-angle glaucoma (OAG) or ocular hypertension: 31 were taking one drug and 31 were taking two drugs. An electronic event medication monitoring device was used to record each bottle opening. The main outcome measures were dosing errors (number of under-adherence or over-adherence events) and coverage (proportion of pharmacologic duration covered by dosing) relative to the ophthalmologist-prescribed regimen.

RESULTS

Adherence to the prostaglandins once daily was good in both groups by all measures (<or=10% of subjects with more than five dosing errors and mean coverage of 97.2% +/- 6.1%). Adherence to the second medication in the two-drug group was poorer (37% of subjects with more than five dosing errors and mean coverage of 85.6% +/- 12.6%). For the subjects using beta-adrenoceptor antagonists, 24.8% +/- 18.4% of doses were taken at less than 10-hour intervals (over-adherence).

CONCLUSIONS

The incorporation of a time component in electronic monitoring provides more information than prescription refill rate or other methods. We found that more complex dosing regimens result in poorer adherence, although once-daily drugs in a complex dosing regimen were found to have good adherence.

Impact of Physicochemical and Structural Properties on the Pharmacokinetics of a Series of α1L-Adrenoceptor Antagonists

A rational drug discovery process was initiated to design a potent and prostate-selective alpha1(L)-adrenoceptor antagonist with pharmacokinetic properties suitable for once a day administration after oral dosing, for the treatment of benign prostatic hyperplasia. Two series of compounds based on a quinoline or quinazoline template were identified with appropriate pharmacology. A series of high molecular weight cations with high hydrogen-bonding potential had extensive in vivo clearance, despite demonstrating metabolic stability. Studies in the isolated perfused rat liver and fresh rat hepatocytes indicated that active transport protein-mediated hepatobiliary elimination is an efficient clearance process for these compounds. A reduction in molecular weight and hydrogen-bonding potential resulted in a second series of compounds with in vivo hepatic clearance predictable from in vitro metabolic clearance. Initially, lipophilicity was reduced within this second series to reduce metabolic clearance and increase elimination half-life. However, this strategy also resulted in a concomitant reduction in volume of distribution and a negligible effect on prolonging half-life. An alternative strategy was to increase the intrinsic metabolic stability of the molecule by careful structural modifications while maintaining lipophilicity. Replacement of the metabolically vulnerable morpholine side chain resulted in identification of UK-338,003, (N-[2-(4-amino-6,7-dimethoxy-5-pyridin-2-yl-quinazolin-2-yl)-1,2,3,4-tetrahydro-isoquinolin-5-yl]-methanesulfonamide), which fulfilled the objectives of the discovery program with suitable pharmacology (human prostate alpha1(L) pA(2) of 9.2 with 25-fold selectivity over rat aorta alpha1(D)) and sufficiently long elimination half-life in human volunteers (11-17 h) for once a day administration.

Adherence with montelukast or fluticasone in a long-term clinical trial: results from the mild asthma montelukast versus inhaled corticosteroid trial

BACKGROUND

Nonadherence with asthma therapy is common and may contribute to poor clinical outcomes.

OBJECTIVE

To examine the effect of dosing frequency and mode of delivery of therapy on adherence and clinical outcomes.

METHODS

We examined adherence in patients with mild persistent asthma (15-85 years) enrolled in a randomized study of montelukast (10 mg once daily) or fluticasone (88 microg, 2 puffs twice daily) during a 12-week double-blind treatment period (DB), followed by a 36-week open-label trial (OL). Adherence was monitored using eDEM for montelukast/placebo and MDILog devices for fluticasone/placebo.

RESULTS

Participants used at least 1 puff of inhaled therapy on 83.3% DB/76.8% OL of days and at least 1 dose of oral therapy on 77.5%/71.4% of days (P < .0001). Subjects used inhaled therapy less than prescribed on 49.5%/57.5% of days, compared with 22.5%/28.6% of days for oral therapy (P < .0001). In the DB, a dose-response relationship was observed with fluticasone and asthma rescue-free days (P = .02) and FEV(1) percent predicted (P < .01) only for patients with FEV(1) < or = 86%. In the OL period, a dose-response relationship was observed with fluticasone and FEV(1) percent predicted (P < .001).

CONCLUSION

Whereas subjects were more likely to use inhaled fluticasone/placebo at least once a day, subjects were more likely to take once-daily oral montelukast/placebo as prescribed. Clinical outcomes were inconsistently associated with adherence levels.

CLINICAL IMPLICATIONS

Patients were less likely to be fully adherent with twice-daily therapy than with once-daily therapy, but most still achieved adequate asthma control.

When drugs don't work: economic assessment of enhancing compliance with interventions supported by electronic monitoring devices

Non-compliance with prescribed regimens poses a significant problem in clinical therapeutics - patients who do not take their medications according to the labelling instructions are at higher risk of treatment failure, and this may have adverse effects on health outcome and healthcare costs. There is increasing evidence on strategies aimed at improving compliance, but most studies do not implement an unbiased technique for measuring compliance. Patients and clinicians alike are notoriously unreliable in assessing compliance; the use of electronic compliance-monitoring devices (ECMDs) is one of the most robust ways to identify non-compliance and assess the effectiveness of interventions aimed at promoting compliance. ECMDs may also form a part of the intervention, by allowing the health professional to provide feedback to the patient on his/her dosing history. This approach has been referred to as a 'measurement-guided medication management (MGMM) programme'.This article reviews the evidence on the effectiveness of MGMM programmes based on ECMDs, and sets out a framework for assessing their economic value. Existing studies focus primarily on the impact of MGMM programmes on compliance. However, to generalise to other settings, including routine practice, further evidence is required on their clinical and cost effectiveness. Specifically, more studies are required to assess whether the observed improvements in compliance translate to improvements in health outcomes, and whether these may be achieved in a cost-effective manner.