Development of prescribing indicators for elderly medical inpatients

AIMS

To identify and improve suboptimal prescribing for elderly patients we have developed a number of prescribing indicators which focus on areas of concern and allow evaluation of the benefit of interventions. We report here on fourteen indicators.

METHODS

The indicators are of three types: a) purely descriptive with no attempt to define optimal values, e.g. number of items prescribed per patient; b) based on unnecessary or potentially harmful prescribing, e.g. duplication; c) assessing the appropriateness of prescribing specific drugs or combinations e.g. digoxin and warfarin/aspirin in atrial fibrillation (AF). Appropriateness was defined on the basis of objective research findings and involved comparing individual patient clinical records to criteria for appropriate prescribing. Prescribing and personal data were collected for medical inpatients aged 65 years or over in 19 hospitals in England and Wales. A total of 1686 patients were included, median age 81 years, 41% were male.

RESULTS

Patients were prescribed 11475 items, mean 4.6 regular items per patient. Completion of drug allergy/sensitivity statements varied from 3 to 93% between units. Use of generic name and specification of a maximum frequency of administration for "as required' medicines were more consistent, ranging from 76-94% and 52-81% respectively. Little duplication of therapy was seen. Benzodiazepines were prescribed for 22% patients, but were appropriate in only approximately one third of these. Of the 2% patients prescribed an angiotensin converting enzyme inhibitor with a potassium-sparing diuretic or potassium supplement, prescription of the combination was appropriate in 84%. Coprescription of steroids with beta 2-adrenoceptor agonists appeared excessive in 67% patients receiving a beta 2-adrenoceptor agonist, as only 51% had documented evidence of steroid responsiveness or another indication for steroids. Stroke prophylaxis in AF was inadequate: 22% patients prescribed digoxin also received warfarin or aspirin 300 mg whereas 64% should have received the coprescription.

CONCLUSIONS

These prescribing indicators are sensitive to inappropriate prescribing for elderly medical inpatients and cover a wide range of therapeutic areas. They should enable changes in prescribing quality to be measured objectively. Interhospital variation in casemix resulted in substantial differences in the proportion of patients in whom it would have been appropriate to prescribe specific drugs or combinations and prevented derivation of reference ranges of optimal prescribing for four indicators.

Aspartame pharmacokinetics - the effect of ageing

Aspartame is an intense sweetener which is increasingly used in the UK. It is registered at an acceptable daily intake (ADI) of 40 mg/kg, although there are no previous data relating to the metabolism of aspartame in older people. Twelve young and 12 elderly volunteers each received a single dose of approximately 40 mg/kg of aspartame. Baseline concentrations of phenylalanine (the main metabolite of aspartame) rose after ingestion with a significantly higher maximum concentration (Cmax) (81.3 vs. 63.3 micromol/1, p<0.01) and area under the plasma concentration-time curve extrapolated to infinity AUC 9(0-infinity)(518.7 vs. 353.5 micromol . h/l, p<0.01) in the elderly group. The higher concentrations reflected a significant fall in volume of distribution (V) from 2.03 to 1.59 1/kg (p <0.05) and clearance (CL) from 7.3 to 4.9 ml/min/kg (p <0.005) in the elderly group. The greater effect on CL than on V resulted in a small but non-significant rise in elimination half life (3.5 to 3.9 hours). The sizes of the differences were modest implying that there is no need on pharmacokinetic grounds for a change in the ADI for older people.

Hawksley random zero sphygmomanometer versus the standard sphygmomanometer: an investigation of mechanisms

There has been recent controversy over the accuracy of the Hawksley random zero sphygmomanometer (RZS). In most instances, there has been a bias towards lower recordings with the RZS. In an attempt to identify the mechanism, we designed a study to test the hypothesis that biased error is due to: (1) the magnitude of the random zero; and (2) the magnitude of the pressure being recorded. A RZS (60 mm Hg zero UK version) was connected via a Y-tube to a standard mercury sphygmomanometer (SMS). The circumference of the cam responsible for the variable reservoir size in the RZS was marked into quarters. Within each 10 mm Hg band from 300 to 60 mm Hg, 12 paired readings were taken randomly: three within each of the four quarters of the cam circumference. The mean SMS value was 148.8 vs. 148.2 mm Hg for the RZS. Although of minimal biological significance this difference was highly significant (t = 6.2; p < 0.0001). Our findings fail to confirm the difference between RZS and SMS previously reported and we did not find any evidence of a relation in the difference between SMS and RZS and either the random zero value or the height of the blood pressure. Our findings suggest that if the RZS does under record BP versus the SMS it may relate to a patient-machine interaction not detectable in our system.

Twenty-four-hour ambulatory blood pressure monitoring in healthy elderly people: reference values

One hundred and two healthy elderly volunteers (aged 65-83 years) underwent 24-hour ambulatory blood pressure monitoring. Mean day- and night-time pressures were higher than reported for younger subjects. Removing outlying BP measurements from individual 24-hour recordings only minimally affected mean figures of the group but in some individuals mean day diastolic BP may be up to 5 mmHg lower on editing. Using unedited data, mean day and night pressures were 134/81 mmHg and 119/67 mmHg respectively (corresponding 95th centiles 160/96 mmHg and 146/84 mmHg) and systolic and diastolic BP loads were 36% and 21%. These values may be used as temporary reference values for elderly subjects pending the results of longitudinal studies. Studies quoting ABPM data should specify whether data editing has been employed and, if so, the editing thresholds should be stated.

Investigation of ambulatory blood pressure monitoring data editing criteria

Ambulatory blood pressure monitoring (ABPM) allows multiple measurements of BP over a 24h period but often produces a proportion of measurements which are distant from the mean and unlikely to be genuine. The software which accompanies the SpaceLabs 90207 monitor requires criteria to be set which excludes outliers (autoediting) but there is no published data evaluating at what levels these autoediting criteria should be set. This study set out to ascertain whether outlying BP measurements represent true blood pressures or machine error, the determinants of machine error and appropriate autoedit criteria. Twenty subjects, both normotensive and hypertensive, were studied by ABPM with a blinded observer recording BP using a standard mercury sphygmomanometer (SMS) connected via a T-tube during three activity phases: sitting with cuffed arm still, walking but keeping arm still during measurement and sitting but gently moving the arm during measurement. The results show that a high ABPM/SMS discrepancy is associated with arm movement. After studying different autoediting criteria which aimed to eliminate the maximum number of conflicting readings while excluding the minimum number of unconflicting readings, an autoediting threshold of between 1.75 and 2 s.d.s from the mean based separately on sleep and awake measurements is suggested.

Pharmacokinetics and prescribing in the elderly

The use of prescribed medication in general is higher in the elderly than in the young and it is possible that existing patterns of antimicrobial agent prescribing may predispose to suboptimal response, certain adverse drug reactions (ADR) and the emergence of resistant strains of organisms. Age is an important variable affecting the pharmacokinetics of drugs, including many antimicrobials. Changes which may affect Cmax/MIC ratios and/or the time above MIC include reduced first-pass metabolism, altered distribution volume, reduced binding to albumin, reduced metabolic biotransformation and reduced renal elimination. Application of a knowledge of antimicrobial agent pharmacokinetic changes with age and their implications for response may enable more precise determination of dose regimens for older patients, which is probably desirable for the prevention of both ADR and bacterial resistance.

The pharmacokinetics and pharmacodynamics of medifoxamine after oral administration in healthy elderly volunteers

The pharmacokinetics and psychomotor effects of medifoxamine, a 5 HT reuptake inhibitory antidepressant, were studied in healthy elderly volunteers after single and multiple dosing. The elimination half life (t1/2z) after single doses of 300 mg was 2.8 h--almost identical to that found in young volunteers. After seven days of dosing at 100 mg three times daily the mean corrected AUC after 300 mg significantly increased from 1.04 to 1.34 mg.h.l-1 and t1/2z increased to 4.0 h (NS). There were no significant changes in critical flicker fusion frequency, symbol digit substitution, continuous attention or choice reaction times.

Psychomotor performance and antihypertensive treatment

1. The aim of treatment of hypertension is prevention of cardiovascular complications without adverse drug reactions. Psychomotor performance can be measured objectively yet there remains uncertainty concerning the psychomotor effects of antihypertensive drugs during chronic treatment. This uncertainty is partly due to the confounding adverse effects of cerebrovascular disease and hypertension itself. There are as yet insufficient good quality data on psychomotor effects with which to differentiate between the commonly used agents. However, in general, the beneficial effect of lowering blood pressure tends to more than offset any adverse effects of the agent used.

Assessment of changes in psychomotor performance of elderly subjects

1. The repeatability of a computerised psychomotor test battery on a day-to-day and week-to-week basis was assessed by determining its test-retest reliability and variations in group-means and intraindividual psychomotor performance scores of elderly people. 2. Psychomotor performance was assessed in 50 well-screened elderly subjects (21 males, 29 females; mean age 70.4 +/- 5.0 (s.d.) years) on 5 consecutive days and over 4 weeks in standardised test conditions. 3. The psychomotor test battery consisted of computerised versions of symbol digit substitution test (SDST), continuous attention test (CAT), choice reaction time (CRT), critical flicker fusion test (CFFT), cognitive flexibility test (FLEX), paired word association test (PWAT) and inspection time (INSP). 4. Main outcome measures were test-retest reliability, group variability and intraindividual variability. 5. There was no significant variation in group-means for all components of the test battery over 5 days or 4 weeks on two way analysis of variance. The intraindividual coefficient of variation was low for SDST, CRT, CFFT, FLEX, PWAT and INSP during the period of assessment. Test retest reliability was greater than 0.8 for SDST, CAT, CRT and PWAT. 6. Tests in the Automated Psychomotor Test Battery are reliable and repeatable measures of psychomotor performance on a day-to-day and week-to-week basis.

Computerised psychomotor performance testing: a comparative study of the single dose pharmacodynamics of minaprine and amitriptyline in young and elderly subjects

The psychomotor and cardiovascular effects of minaprine 100 mg, a novel antidepressant, were compared with amitriptyline 25 mg, as a positive control, and placebo in a single dose randomised double-blind crossover trial using an automated psychomotor test battery (APT), postural sway (PS), blood pressure (BP) and pulse in nine young and nine elderly healthy subjects. Analysis of variance, taking into account baseline values, showed that continuous attention test (CAT), critical flicker fusion threshold (CFFT), decision making test (DMT) and paired word association (PWA) were significantly impaired with amitriptyline compared with minaprine and placebo. Minaprine did not differ from placebo. Amitriptyline significantly lowered supine systolic blood pressure (BP) and all treatments produced significant decreases in heart rate in young and elderly. No age effect on psychomotor performance was seen. Minaprine compared favourably with amitriptyline using the APT with the doses used. The APT is useful in the evaluation of new drugs on psychomotor performance.

Effect of antihypertensive treatment on psychomotor performance in the elderly

The psychomotor effects of control of hypertension were studied in a parallel group comparison of 25 elderly hypertensives (aged 61-79 years; SBP = 192 (range 162-212) mmHg; DBP = 112 (range 98-124) mmHg) shown to have psychomotor impairment when not on antihypertensive treatment. Single blind treatment was commenced with placebo or a diuretic: atenolol, nifedipine or captopril (5 x n = 5). A range of tests using an automated psychomotor test battery showed a significant improvement compared with placebo in tests of attention and psychomotor speed in subjects rendered normotensive (n = 18) after treatment for one week (SDST + 3.8, P < 0.001; CAT + 1.2, P < 0.03; PWAT + 1.9, P < 0.004; INSP -49.5 ms, P < 0.001). Subgroup analysis suggested greater improvement in psychomotor performance with captopril, but this was equivocal because of the small sample size in each group. Hence, the psychomotor effects of treatment with nifedipine and captopril were compared in a further 13 hypertensives (aged 62-76 years; SBP = 178 (range 169-193) mmHg; DBP = 106 (range 97-117) mmHg) in a double-blind crossover study. With both drugs, control of hypertension was associated with a significant and comparable improvement in several psychomotor performance measures. The results suggest that impaired psychomotor performance due to hypertension improves with antihypertensive treatment. The improvement appears to be related to control of hypertension rather than to the direct CNS effects of antihypertensive drugs.

Psychomotor performance in elderly hypertensive patients

The psychomotor performance of 25 elderly patients with mild to moderate hypertension (aged 62-78 years, SBP = 162-212 mmHg; DBP = 98-124 mmHg) was compared with 25 age-matched controls (SBP = 110-160 mmHg; DBP = 64-92 mmHg). The hypertensive subjects did not have evidence of target-organ damage and were on no antihypertensive treatment at the time of assessment. Performance on a range of tests: symbol/digit substitution test (SDST) (34.3 vs. 39.5, P < 0.01), continuous attention test (CAT) (33 vs. 36.2, P < 0.01), choice reaction time (CRT) (270 ms vs. 320 ms, P < 0.01), paired word association test (PWAT) (4.1 vs. 7.0, P < 0.001) and inspection time threshold (INSP) (158 ms vs. 52 ms, P < 0.001), showed significant impairment in the hypertensive group compared with controls. These differences did not correlate with the duration of hypertension or degree of BP elevation. The impairment in hypertensive subjects was stable over a four week period. These results suggest the occurrence of a functional and possibly reversible impairment of psychomotor performance in elderly hypertensive patients which may have implications for antihypertensive treatment.

ABC of sleep disorders. Sleep and sleep problems in elderly people

Images

The association of age with gastric emptying

Gastric emptying is important as a rate-limiting step in the absorption of orally administered drugs. Paracetamol absorption kinetics were used to compare gastric emptying in 19 fit elderly and 19 fit young volunteers. The results showed no significant difference in any of the derived parameters (t1/2abs, tlag and tmax) between the two groups. These results suggest that ageing does not impair this rate-limiting step in drug absorption.

A comparison of the central nervous system effects of caffeine and theophylline in elderly subjects

1. The effects of oral administration of 250 mg caffeine or theophylline and placebo on subjective ratings and psychological test performance were studied in a double-blind crossover experiment in 20 healthy elderly subjects. 2. Performance on the continuous attention task showed a significant improvement compared with placebo with both active treatments. Performance with caffeine was significantly better than with theophylline. Mean error index scores (normalised AUCs) were: placebo--0.130; caffeine--0.083; theophylline--0.093. No other objective measure shows significant treatment effects. 3. Subjective ratings showed that subjects felt significantly more alert on caffeine than on either theophylline or placebo. Subjects also rated themselves as more energetic and interested on caffeine than on placebo. 4. Plasma concentrations of caffeine were lower than those of theophylline (mean 5.76 and 8.72 mg l-1 respectively at 2 h post-drug. 5. These results suggest that caffeine is a more potent CNS stimulant than theophylline.

Comparative assessment of enprofylline and theophylline for chronic obstructive airways disease in the elderly

Enprofylline, a recently developed xanthine derivative, is a more potent bronchodilator than theophylline. This study compares the efficacy and safety of enprofylline with theophylline for chronic obstructive airways disease (COAD) in elderly subjects. The study was of a randomized double-blind parallel design and commenced with a 1-week reference period when oral bronchodilators were withdrawn. Patients were then treated with either enprofylline or theophylline 150 mg bd for 2 weeks (period 1) followed by 300 mg bd for a further 3 weeks (period 2). Patients recorded peak expiratory flow rate (PEFR) and adverse experiences, if any, in a diary, daily. Of 111 patients recruited for the study, 85 entered active treatment (theophylline, n = 44; enprofylline, n = 41). Mean age was 72 years and mean bronchodilator reversibility was 22%. Enprofylline increased mean morning PEFR by 11% (period 1) and 19% (period 2) whereas theophylline increased PEFR by 13% and 19%, respectively. From the enprofylline group 29% were withdrawn from the study due mainly to headache and nausea/vomiting and from the theophylline group 7% were withdrawn due mainly to nausea/vomiting. Mean plasma concentrations of enprofylline were 2.0 mg l-1 and 3.4 mg l-1, and with theophylline 5.4 mg l-1 and 10.0 mg l-1 at the end of periods 1 and 2, respectively. Enprofylline and theophylline produced similar improvements in lung functions and symptoms of chronic obstructive airways disease, but enprofylline was less well tolerated than theophylline.

Pharmacodynamics: changes in homeostatic mechanisms, receptor and target organ sensitivity in the elderly

Response to drugs in the elderly may be accentuated or modified by age related changes in homeostatic mechanisms such as postural control, orthostatic circulatory responses, thermoregulation, visceral muscle function and higher cognitive function. Changes in specific receptor and target organ responses have also been described. beta-Adrenoceptor-mediated effects are apparently attenuated by a reduction in high affinity binding sites and altered post receptor mechanisms resembling desensitization. alpha 2-Adrenoceptor and cholinergic effects may also be attenuated though there is no evidence for altered alpha 1-adrenoceptor sensitivity. The effects of age on sensitivity to benzodiazepines, calcium channel blocking agents, angiotensin converting enzyme inhibitors, anticoagulants and cardiac glycosides are also discussed. There is a major requirement for further work in this field.

Adenosine-induced respiratory and heart rate changes in young and elderly adults

The effects of intravenous boluses of adenosine on respiration and heart rate were compared in young and elderly individuals. Respiratory stimulation and biphasic changes in heart rate were confirmed. The dose-response relationship for the effects of adenosine on respiration and heart-rate did not differ significantly between 10 young (mean age 25.2 +/- 4.9 years) and 10 elderly (mean age 66 +/- 3.1 years) drug-free individuals, indicating that age is unlikely to be a major determinant of adenosine responsiveness.

Ethical aspects of clinical research in the elderly

It is of major importance to acquire hard information on which to base more accurate diagnostic criteria and to decide which forms of treatment are of proven benefit to older patients. At the same time the ethical and practical difficulties entailed demand special care, sensitivity, expertise and patience.

Effects of caffeine on vigilance and other performance tests in normal subjects

In two randomized double-blind crossover studies, 8 and 10 healthy volunteers took either 200 mg caffeine or placebo. Objective and subjective measures of caffeine effects were carried out over the following 1-3.5 h. Auditory vigilance, a test lasting 1 h, showed significantly better performance on caffeine than on placebo. In the second study, this effect was only apparent in the second half of the test. Of the shorter objective tests used, only finger tapping showed a significant effect of caffeine, the rate of tapping over 1 min being increased. The subjective assessments showed increased interest and alertness in the caffeine session. Reliable detection of the effects of mild stimulant drugs using objective measures may require the use of tests of long duration.

"First-dose" response to mianserin: effects of age

The effects of single 10 mg oral doses of the antidepressant mianserin on psychomotor performance, subjective sedation and supine and standing blood pressure were compared in ten young and nine elderly healthy volunteers. Immediate and residual sedation following this subtherapeutic dose was readily detected in both groups. In contrast to previous studies with benzodiazepines, the sedation effect was not accentuated in the older subjects. Subjective awareness of sedation was significant in the young but not, however, in the elderly. "First-dose" postural hypotension, presumably due to post-synaptic alpha-blockade also occurred in young subjects only. Caution may be needed on initial dosage of mianserin in young individuals who drive or undertake skilled tasks and in the elderly who may be unaware of psychomotor impairment. The reported alpha 2 receptor selectivity of mianserin might explain the lack of postural effects in the elderly, and might constitute a potentially useful characteristic in the development of new compounds.