Australian trends in opioid prescribing for chronic non-cancer pain, 1986-1996

Abstract

MJA 1997; 167: 26-29

Introduction

The aims of this study were to describe trends in opioid prescribing for chronic non-cancer pain, to investigate whether a person who begins taking oral opioids regularly will continue to do so in the long-term, and to assess the extent to which opioid treatment is associated with dose escalation over time.

Methods

• Records from the Commonwealth Department of Health, Housing and Community Services. This organisation maintains records of drugs consumed in each State, and officers of the department provided data on national and State consumption of Schedule 8 (S8) opioid drugs for the years 1984-1995. Figures on oral opioid consumption obtained from the Commonwealth give a State by State breakdown on all morphine preparations except morphine mixtures. For the years 1986-1988 use of these morphine mixtures in each State was documented State by State, and NSW accounted for 50%-66% of national consumption; after 1988 only figures for national consumption are available. For the purposes of this study, NSW consumption of morphine mixtures after 1988 was estimated to be 55% of national consumption. By 1995 morphine mixtures accounted for less than 20% of total oral morphine consumption, so inaccuracy in this estimate is unlikely to alter greatly the overall trend in oral morphine use.

• Monthly summaries of authorities to prescribe S8 drugs from the Pharmaceutical Services Branch (PSB) of the NSW Department of Health. It is a legal requirement in all Australian States that regular prescribing of S8 drugs to any individual patient beyond a certain minimum period requires an authority. The issued authorities specify whether opioids are prescribed for cancer pain or non-cancer pain, and trends in the issuing of authorities provide an indication of whether there has been an increase in prescribing for non-cancer pain. In NSW, the PSB issues these authorities, and since 1990 the department has prepared a monthly summary of all current authorities. Summaries for the month of June each year were used to estimate trends in the point prevalence of authorities to prescribe opioid drugs from 1990 to 1996.

• Individual patient files held by the PSB. Applications for an authority to prescribe S8 drugs are reviewed by a medical committee, and new applications are usually approved if supported by someone with specialist medical qualifications. Most authorities are issued for 6 or 12 months, at which time a repeat application must be lodged, usually accompanied by a clinical report on the patient's progress. Thus, there is a record of reports and letters which have been submitted supporting applications to prescribe S8 drugs. From these records a cohort of patients was identified for whom a new authority (i.e., not a continuation of a previous authority) was issued in February and March, 1991, to prescribe an opioid drug in non-cancer pain. Records for this cohort were followed up for five years. Files were studied to ascertain in each case whether the patient continued taking S8 drugs for the full five years, whether their daily dose of opioid escalated over time, and to identify their diagnoses and comorbidities.

The study was approved by the ethics committee of the South Eastern Sydney Area Health Service. The collection of data from NSW Department of Health files was performed by two medical students. No information identifying patients or prescribing doctors was available to any clinician who could have been involved in the patient's care.

Results

Opioid consumption

The Figure (below) suggests that the advent of slow release morphine in 1990 in Australia has had a marked effect on prescribing patterns, as the rate of increase in morphine prescribing accelerated from that point. However, although some individual opioid drugs have declined in use, the increase in oral morphine has not been accompanied by a decline in the use of other opioid drugs.

Figure: Australian consumption of opioids, 1986-1995.

Figures for NSW parallel the Australian rise. Between the years 1990 and 1995, total oral morphine use in NSW rose from 87 to 209 kg per year (a 140% increase). In the same interval, the consumption of other S8 drugs rose from 42 to 46 kg per year (10% increase). Injectable S8 drugs rose from 1.2 to 1.3 million ampoules (8% increase).

Authorities

Follow-up of authority applications

The clinical impression is that dose escalation may be more likely in patients taking the potent, short-acting drug dextromoramide, and less likely in those taking low potency codeine or long-acting methadone. Despite the small numbers (see Box), the difference in the proportion of patients taking these different drug types whose opioid dose escalated approached significance (P = 0.053).

Thirty-three patients (32.4%; 95% CI, 23.4%-42.3%) were still receiving S8 opioids five years later (although many were receiving a different S8 opioid in 1996).

Twenty-six of the 102 patients (25.5%; 95% CI, 17.4%-35.1%) received escalating doses of opioids: 21 of the 33 patients who were still receiving opioids on authority in 1996, and five of the 69 people not receiving opioids on authority in 1996 (chi-squared = 44.69; 1df; P < 0.005). Patients receiving opioids for the full five years were more likely to escalate their dose (odds ratio, 22.4; 95% CI, 7.1-71.0). It is unlikely that escalation was simply a function of patients beginning with a low initial dose of opioid. Converting initial doses to equivalents of oral morphine, the group whose doses did not escalate began with a mean dose of 80 mg of oral morphine per day, while the group whose doses did escalate began with a mean dose of 87 mg per day.

The PSB records documented that 14 patients from this cohort died between 1991 and 1996 (7 men, 7 women; mean age, 70; age range, 42-91). Most were elderly, with serious underlying disease. It seems that in many of these patients, prescribing opioids was part of terminal care. Excluding subjects known to have died, 33 of the remaining 88 subjects (38%) were still receiving opioid drugs on authority five years later. The 55 no longer receiving opioids on authority had received opioids for a mean of 19 months.

Clinical data from authority applications

The comments in the patients' files suggest that in many cases prescribing opioids is a response to difficult and unmanageable problems. There is more than a hint of frustration in many of the comments -- such as the terse letter:

The situation is unchanged. His back feels "like a bag of broken china". I am still at a loss to know what to do and I have arranged to see him again in six weeks with further x-ray.

This patient has been so adversely affected by her CFS [chronic fatigue syndrome] and migraine she has been rendered completely dysfunctional as a human being and mother.

While many of the patients in this study had multiple medical problems and histories of extensive treatment, often there were strong intimations of concurrent psychological and adjustment difficulties. For example, one patient had a history of multiple back operations, with a background of social problems described as "marriage collapsing, alcoholic father living with them, and a history of overdoses on tricyclic antidepressants and on benzodiazepines".

While some of the patients had clearly defined diseases, and several were seriously ill, in 62 cases (61%) there were poorly defined medical problems. In 22 cases there was no clinical information other than a diagnosis. Among the other 80 files, the presence of social and emotional problems was noted in 29 cases (36%). The quality and thoroughness of medical information documented in the health department files was very limited.

Discussion

The national data on overall opioid use are an accurate measure of the quantity of these drugs being prescribed each year. However, there are limitations on the use of official records in determining how much of this increase was for terminal care, and how much for chronic pain. In this study, the increase in authorities current in NSW was about half as great as the increase in oral morphine use between 1990 and 1995. Given that oral morphine is seldom used in acute pain management, the disparity between authorities and total amount of drug used suggests that many patients receive morphine for prolonged periods without an authority to prescribe having been issued. There is no way of knowing how many doctors prescribe opioids long-term to individual patients without ever seeking authority. Furthermore, it is possible that there is a systematic bias, with doctors prescribing for terminal care being less likely to apply for an authority than when prescribing for chronic non-cancer pain. However, even with these reservations, it seems reasonable to conclude that the increase in authorities in both categories and the increase in overall use of morphine indicate a change in attitudes to opioids, with more liberal use in both terminal care and chronic pain.

Might this more liberal approach contribute to a problem with iatrogenic drug dependence? The hallmark of opioid dependence is that it is a chronic, relapsing, long-term problem. Most of the 102 patients who began taking opioid drugs on authority in early 1991 were no longer doing so five years later. However, some of them may have continued to receive opioids without an authority. Patients who move interstate, find a new doctor who does not seek an authority to prescribe or who "doctor shop" to get prescriptions from multiple prescribers may not appear in the health department records even though they continue to receive opioids. Some may have switched to agents such as combined paracetamol-codeine, a drug containing a modest dose of opioid, but for which no authority is required. It is also possible that some patients died without this coming to the attention of the health department. However, even allowing for these possibilities, the figures suggest that fewer than half the surviving patients were still taking opioids regularly five years after first taking them.

It is difficult to assess the extent of problems of tolerance and dependence from the incomplete clinical data in official records. Previous studies on selected groups being treated in specialist facilities have reported that opioids can be used safely and effectively,^3,4 but these reports give little indication of the extent to which problems are likely to arise in more diverse samples of patients treated in a range of settings.

Dose escalation may not be a reliable indication of dependence, but may reflect changes in pathology. However, previous reports indicate that most patients with non-cancer pain do not require escalating doses over time.⁶ Clinical experience with cancer pain management indicates that during the first weeks of dosing with opioids a degree of tolerance is reached, but this reaches a plateau and thereafter a stable dose can be beneficial for prolonged periods.⁷ The system of S8 authorities means that patients have usually been receiving opioids for a couple of months before authority application, and by then should usually be receiving a stable and effective dose. Most patients discontinued opioid use after quite prolonged periods without dose escalation. It is likely that among the 25% whose dose escalated there were many patients with problems of dependence.

The comments and diagnoses in the files indicate that opioids are often prescribed for patients with social problems, high levels of emotional distress, and unclear medical diagnoses. It is likely that many of these subjects have a mixture of somatoform disorders and diverse medical and psychosocial problems. The benefits and risks of opioid use in this setting are poorly understood. A supportive doctor-patient relationship and attention to psychiatric and medical comorbidity are more important aspects of the management of somatoform disorders.⁸ The value of psychological treatment has been demonstrated in recent randomised trials.⁹ The implication for treating chronic pain states where there appear to be contributing psychological or social factors is the need for a comprehensive approach to treatment.

Opioid drugs may have a useful role in such a comprehensive approach. The risks of opioid dependence, with escalating pain and drug use and diminished activity, need to be set against the potential benefits in terms of improved pain control and well being. It has been suggested that the risks of dependence can be minimised when the drugs are prescribed by experienced and skilled medical practitioners.³ It is also probable that the current system of requiring doctors to obtain authorities to prescribe opioids long term is a valuable restraint on inappropriate prescribing of these drugs.

Acknowledgements

References

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