Use of an electronic monitoring aid to investigate the medication pattern of analgesics and non-steroidal anti-inflammatory drugs prescribed for osteoarthritis

S. PUNCHAK, L. I. GOODYER1, and F. MISKELLY2

Department of Pharmacy, University of Malaysia, Malaysia,
1 Department of Pharmacy, King's College London and
2 Department of Medicine for the Elderly, Charing Cross Hospital, London, UK

SIR, If a patient with arthritis continues to suffer pain, the possibility of deviation from the prescribed dosing regimen should be taken into account when reviewing medication. Simple measures of assessing compliance such as tablet counts only indicate the total number of tablets consumed over a period of time and not the frequency or pattern with which medication was taken. Electronic medication monitoring aids (EMMA) provide more detailed information on medication patterns for individual patients [1]. The aim of this study was to use an EMMA, specially designed for use by elderly arthritic patients, to identify the self-medication pattern of analgesic and non-steroidal anti-inflammatory drugs (NSAIDs).

This was a prospective cohort study of self-medicating elderly patients with a diagnosis of osteoarthritis and taking NSAIDs or analgesics.

The EMMA consisted of a small box 6'' x 4'' x 3'' with two compartments. A PSION handheld computer was located in the lower compartment and in the upper was placed the patient's medication. On each occasion the box was opened, the precise time and date was recorded in the computer's internal memory and downloaded to a PC for analysis. The nature of the box was explained to the patient and they were aware that recordings were being made. The dosage interval was calculated as the time between one box opening and another on those days that medication was taken. The first reading of each day was that made after midnight. If only one box opening was made during the day the time interval was counted as 24 h. From this an average interval per day over the 21-day period was calculated for each patient.

All patients were visited in their own homes on three occasions. On the first visit written informed consent was obtained and a simple tablet count performed.

On the second visit, 1 week later, a further tablet count was undertaken and the patients provided with an EMMA. The patient's analgesics or NSAIDs were counted and placed in the box. Patients were instructed to take their tablets in exactly the same manner as previously. If the patient received both types of medication, the analgesic was used in preference. Three weeks later the monitoring device was collected and a further tablet count made.

At no time was an attempt made by the researcher to improve compliance or to discuss the medication being used.

Of the 110 patients who fitted the inclusion criteria and agreed to participate 85 completed the study.

There was little change in the tablet counts between the period before and that following the introduction of the EMMA.

There was a tendency for a fall in measured dosage interval with increased frequency of dosing (Table 1Go) when the medication was prescribed to be taken on a regular basis, and this difference between prescribed regimens was statistically significant (P < 0.05). However, over half the patients were prescribed medication to be taken ‘when required’.


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TABLE 1. Comparison of prescribed dosage regimens and dosage intervals recorded by EMMA

 
Other studies [2, 3] have examined compliance to prescribed NSAID therapy. A generally low level of compliance was reported, and Knight et al. [2] suggested patients tended to regard them as analgesics for a ‘when required consumption’. These previous studies employed tablet counts rather than electronic monitors. The present study confirms, using an EMMA, that arthritic patients adopt their own medication pattern for both NSAIDs and analgesics, at some variance to the prescribed dosage.

Similar results were obtained in a recent study investigating compliance to a once daily NSAID for ankylosing spondylitis using an electronic monitor [4]. However, these workers noted a high level of extra dosing days by some patients, not observed in the present study amongst those prescribed once daily medication.

It would be expected that the more frequently the medication is prescribed, the shorter the interval between measured box openings, as seems to be the case. However, the mean interval between doses did not fall below 15 h even for the 6-hourly prescribed regimen. This supports other studies [5–7], that a twice daily dosage is the maximum frequency compatible with reasonable compliance particularly in the elderly.

This study indicates that despite the prescribed dosage regimen, most elderly arthritic patients would tend towards taking their medicines once or twice a day. This should be considered when prescribing analgesics or NSAIDs if regular medication is thought appropriate.

Notes

Correspondence to: L. Goodyer, Department of Pharmacy, King's College London, Franklin-Wilking Building, 150 Stamford Street, London SE1 8WA, UK. Back

References

  1. Urquhart J. Role of patient compliance in clinical pharmacokinetics. Clin Pharmacokinet1994;27:202–15.[ISI][Medline]
  2. Knight JR, Campbell AJ, Williams SM, Clark WJ. Knowledgeable non-compliance with prescribed drugs in elderly subjects—a study with particular reference to non-steroidal anti-inflammatory and antidepressant drugs. J Clin Pharm Ther1991;16:131–7.[ISI][Medline]
  3. Dunbar J, Dunning EJ, Dwyer K. Compliance measurement with arthritis regimen. Arthritis Care Res1989;2:S8–16.[Medline]
  4. De Klerk E, Van der Linden SJ. Compliance monitoring of NSAID drug therapy in ankylosing spondylitis, experiences with an electronic monitoring device. Br J Rheumatol1996;35:60–5.[ISI][Medline]
  5. Eisen SA, Miller DK, Woodward RS et al. The effects of prescribed daily dose frequency on patient medication compliance. Arch Intern Med1990;150:1881–4.[Abstract]
  6. Kruse W, Eggert Krusse W, Rampaier J et al. Compliance and adverse drug reactions: a prospective study with ethinylestradiol using continuous compliance monitoring. Clin Invest1993;71:483–7.[ISI][Medline]
  7. Urquhart J. Ascertaining how much compliance is enough with outpatient antibiotic regimens. Postgrad Med J1992;68(Suppl. 3):S49–58.[ISI][Medline]
Accepted 28 October 1999





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