Does urinary salbutamol reflect compliance with the aerosol regimen in patients with asthma?

A critical evaluation of the methodology of the literature on medication compliance

OBJECTIVE

To develop a simple evaluation tool to assess methodologic rigor of the literature on patient compliance with medications, and to apply the tool to a sample of the literature.

METHODS

A computerized search of the MEDLINE database (January 1980-December 1996) was performed. All English-language articles on compliance with medications were identified, using the MeSH terms patient-compliance and drug-therapy. A 10% sample was then randomly selected for review. Methodologic rigor was assessed on eight standards: study design, specification of patient sample, power analysis, specification of disease, specification of therapeutic regimen, duration of follow-up, definition of compliance, and compliance measurement. The raw scores of the eight standards were then combined in three summary scores, standardized from 0 to 100: study design, disease-related features, and compliance issues.

RESULTS

Seventy-two articles from 719 identified were reviewed. The majority of the research articles were descriptive (63.9%), and patients in these studies were selected mainly from a convenience sample (41.7%). Just nine studies were multicenter studies, and three employed power analysis. The compliance definition was replicable in 41.7% of the studies. In 22 articles neither the compliance measure nor the criteria were stated. One-quarter of the studies (18) used a nonvalidated measure of compliance. Only two studies reached a score of 6 in the compliance measure, and eight studies used two different measures of compliance simultaneously. The median values in the summary scores were: study design 8.3, disease 42.9, compliance issues 50.

CONCLUSIONS

The quality of the compliance research was generally poor. These low scores reflect very important shortcomings in the methodology. Such oversights make it difficult for the reader to critically assess the validity of the conclusions.

Efficacy of a self-management program for childhood asthma--a prospective controlled study

Asthma training programs for parents and children have been developed to increase both the self-management skills of asthmatic children and compliance with medical regimes. In order to evaluate two training programs for asthmatic children aged 7-14, 81 patients were randomly assigned to three groups. Group 1 consisted of 27 patients and their parents who participated in a five-day standardized family-oriented clinical asthma training program. They had monthly follow-up meetings with the training team for a period of six months. Group 2 (n = 29) had the same clinical training without follow-up interventions; a control group (n = 25) received regular medical treatment according to the international guidelines at the asthma clinics without a training program and served as control group. Questionnaires regarding self-management aspects, coping and anxiety were filled out by patients, parents, family doctors and the training team prior to as well as twelve months after the training. The results indicate that Training group 1 benefitted most with respect to active asthma self-management, Training group 2 to some degree while the control group showed no significant effects. The differences after one year between the three groups regarding physical parameters such as lung-function and days missed in school did not reach the level of significance. Our results indicate that the long-term efficacy of self management courses for asthmatic children is enhanced by regular follow-up training sessions.

Single centre open study to compare patient recording of PRN salbutamol use on a daily diary card with actual use as recorded by the MDI compliance monitor

The aim of this study was to assess the patients' use of inhaled short acting bronchodilators as rescue therapy during a 4-week study period. In this study an electronic metered-dose inhaler compliance monitor (MDI-CM) was used to measure the time and date of actuations of the device and this information was then compared with the patients' self reporting diary card (DC). Salbutamol canisters were used in the compliance monitor. The study was approved by the local ethics committee, and written informed consent was obtained from all patients. Patients aged 18 years and over who were either receiving, or in the investigators opinion required, inhaled salbutamol on a PRN basis were enrolled for a 4-week monitoring phase during which all rescue salbutamol used was obtained from the MDI-CM. Patients were recording their use of salbutamol in the DC each morning and evening. There was a 2-week follow-up period following completion of the monitoring phase or withdrawal from the study. Forty-four patients were enrolled and 35 patients completed the study. The mean age (range) was 43 (20-76) years and mean FEV1 2.32 (0.7-4.0) 1, with male:female ratio of 19:25. Comparison of MDI-CM and DC recordings showed patients fell into three categories: (1) patients who used rescue salbutamol appropriately and whose MDI-CM and DC recordings matched closely; (2) patients who used rescue salbutamol for acute relief but whose MDI-CM and DC recordings did not correlate and (3) patients whose use of rescue salbutamol was inappropriate or erratic according to the MDI-CM but whose DC indicated good compliance. This category of patients include those who 'dumped' all their salbutamol before attending clinic appointments. There was no significant difference in the demographic details or the severity of disease in the three groups. Recorded use of 'rescue' bronchodilator is frequently used as an indicator of efficacy for new anti-asthma therapies. This study comparing electronic data monitoring and remembered rescue salbutamol highlights the potential errors that can occur without accurate recording systems.

Investigation of urinary levels of salbutamol in asthmatic patients receiving inhaled therapy

AIM

Some studies have indicated that over-reliance on inhaled bronchodilator (beta 2-agonist) therapy may worsen asthma control and increase morbidity. The aim of this study was to measure urinary concentrations of salbutamol, the most commonly used bronchodilator, in a relatively large sample of asthmatic patients and examine the potential value of the concentration as an indicator of over-use of salbutamol.

METHOD

The urinary concentrations of the drug were measured in 'spot' urine samples from 102 asthmatic patients (64 community patients and 38 hospital inpatients). A solid-phase extraction technique, using a phenyl-bonded phase and a reversed-phase ion-pair high-performance liquid chromatography assay with UV-detection were developed and used to measure both unchanged salbutamol concentrations and total salbutamol concentrations after enzymatic hydrolysis of the metabolite. In addition, salbutamol concentrations were corrected for urine dilution, with the measured drug expressed per gram of urinary creatinine.

RESULTS

The hospital patients were generally older, had greater disease severity, were more likely to be receiving prophylactic therapy and had received more salbutamol in the past 24 h. The urinary concentrations of salbutamol varied enormously between patients. The median concentrations of unchanged and total drug were 0.38 microgram/ml (range 0-34.4 micrograms/ml) and 2.55 micrograms/ml (range 0-49.8 micrograms/ml), respectively. Even when controlling for dosage in the preceding 24 h, there was a 262-fold and 810-fold variation in the urinary concentrations for unchanged and total salbutamol, respectively, among the community patients. Modest correlations were found between salbutamol concentrations and dosage administered in the preceding 24 h (Spearman's r = 0.67 and 0.54 for unchanged and total drug, respectively; P < 0.001). The correlations improved only slightly with correction for urine dilution (Spearman's r = 0.69 and 0.57 for unchanged and total drug, respectively; P < 0.001).

CONCLUSION

This enormous inter-patient variability, which may be largely due to differences in the pharmacokinetics of salbutamol and inhaler technique, may play a role in the observed worsening of asthma control with the regular use of inhaled bronchodilator drugs and warrants further investigation. Measuring urinary concentrations of salbutamol in spot samples provides only a relatively crude indication of the extent of use of inhaled salbutamol in the preceding 24 h.

Health beliefs of adults with asthma: toward an understanding of the difference between symptomatic and preventive use of inhaler treatment

The aim of this study was to examine the potential differences between beliefs relating to symptomatic and preventive inhaler treatment and to analyze the relationship between these beliefs and the use of inhalers by adult patients with asthma in general practice. Unstructured interviews with a stratified sample of 8 patients, taking a combination of salbutamol and beclomethasone inhalers, were used to develop themes for a structured interview, where questions relating to 8 main areas of interest were measured on a 5-point Likert scale. Forty patients prescribed the same combination of inhalers were randomly selected for the structured interview. All agreed to participate (100% response). Correlations between the responses to the 8 themes and measures of inhaler use were analyzed. High use of salbutamol for the relief of symptoms and low use of beclomethasone for the prevention of asthma were common. Perceived benefits of the inhalers, a positive attitude to using the inhalers, and concern about side effects had strong influences on the use of both inhalers. Uncertainty about the inhalers, a negative attitude to using the inhalers, and the involvement of others in asthma management had less influence on inhaler use. Satisfaction with the doctor and the ease of obtaining an inhaler were more important issues for beclomethasone use than for salbutamol use. There are important differences in the beliefs that patients hold in relation to symptomatic and preventive use of inhaler treatment. These findings suggest that focusing on very specific attitudes to treatment may be of benefit in the health education of adults with asthma. Further work is planned to refine the themes so that doctors will be able to explore patients' views about their inhaler treatment by asking a few direct questions.

Measuring adherence to asthma medication regimens

The failure of patients to adhere to physician-prescribed regimens, either pharmacologic or behavioral, has been well documented in medical literature. Poor adherence to asthma medication regimens has been repeatedly demonstrated in both children and adults, with rates of nonadherence commonly reported from 30 to 70%. Medication regimens for asthma care are particularly vulnerable to adherence problems because of their duration, the use of multiple medications, and the periods of symptom remission. The clinical effects of this nonadherence by asthmatic patients can include treatment failure, unnecessary and dangerous intensification of therapy, and costly diagnostic procedures, complications, and hospitalizations. Although the measurement of adherence is an important component of both medical and behavioral interventions to control asthma, relatively little research has directly addressed the reliability and validity of the measures most widely used to assess asthma medication compliance. This review will discuss methods and issues in the measurement of adherence in general, and where available, measures that have been specifically used in evaluating adherence to asthma medication. Common measures used to assess compliance with asthma medications include direct measures, which confirm the use of medication by assaying it in blood, urine, or saliva, or which confirm the to use a medication, such as observed skill in using a metered dose inhaler. Indirect measures infer use with varying degrees of reliability, by use of clinical judgment, self-report/asthma diaries, medication measurement, and electronic medication monitors. The uses and limitations of these measures will be discussed.

Compliance with prescribed drug therapy in asthma

Morbidity and mortality from asthma in the Western world is increasing despite effective prophylactic drugs. Beta agonists are increasingly considered causal; while under-prescribing of inhaled steroids or other anti-inflammatories are accepted as causes for the problems, but the role of non-compliance with inhaled asthma therapy is rarely mentioned. Using a novel electromechanical counter MDI actuations have been recorded in three small (9-11 patients), short (2-3 weeks) studies. When aware compliance with prescribed inhaled steroids was under scrutiny, six patients were fully compliant, two took just 70% of the prescribed regimen, but two did not follow the prescribed regimen at all. When unaware of scrutiny, six out of 11 were compliant but five patients were estimated as taking less than 30-51% of the prescribed dose of inhaled steroid. When asked to monitor rescue bronchodilator usage patients consistently under-recorded. Under-use as well as under prescription of inhaled steroids and under-estimation (8) of beta 2-agonists use may be contributory factors to the present increase in asthma mortality and morbidity. These potential problems of poor compliance need larger scale studies to show how and if behaviour can be altered to improve compliance.

Determination of the relative bioavailability of salbutamol to the lung following inhalation

1. The urinary excretion of salbutamol and its sulphate metabolite was measured following oral (4 mg) and inhaled (4 x 100 micrograms) administration of salbutamol. 2. Total urinary recovery of salbutamol and its sulphate conjugate indicated a mean (s.d.) relative bioavailability of 92.2 (24.8) % following inhalation compared with oral administration. 3. The mean (s.d.) elimination half-lives of salbutamol and its sulphate conjugate were 5.7 (1.4) and 4.1 (2.1) h, respectively, after oral administration and following inhalation they were 6.1 (2.1) and 5.1 (1.0) h, respectively. 4. Following oral and inhaled administration it was found that in the first 30 min the mean (s.d.) percentage of the dose excreted in the urine as unchanged salbutamol was 0.18 (0.14) and 2.06 (0.80) %, respectively (P < 0.01). The drug content of a urine sample taken 30 min after inhalation is, therefore, considered to be representative of the amount of drug delivered to the lungs. It is proposed that this method can be used to evaluate the relative bioavailability of salbutamol to the lung following inhalation by different techniques and devices.

Compliance with inhaled therapy and morbidity from asthma

Patient compliance with a standardized incremental regimen of inhaled anti-asthma therapy has been assessed in a large, prospective study in general practice. Urine salbutamol estimations were made in 30 patients who had the largest improvement with therapy (mean increase in FEV1 0.45 l above baseline: Responsive) and in 30 patients whose airflow obstruction failed to improve (FEV1-0.14 l: Nonresponsive). The urine salbutamol concentrations rose over the 9 month period in the responsive patients as expected with the incremental doses prescribed, and were significantly higher than urine levels in nonresponsive patients at two dose levels. Poor compliance with prescribed inhaled therapy is an important cause of persistent morbidity from asthma.