Opioid prescribing in Australian general practice

Global concern about the prescribing of opioid analgesic medications (particularly oxycodone) for chronic pain is growing. In this Journal in September 2011, Roxburgh and colleagues examined the rise of oxycodone and morphine prescribing and the harm associated with opioid use.1 In the accompanying editorial, Hall and Farrell argued that this suggests that most prescribing of opioids was for chronic non-malignant pain.2 We tested this assertion using general practitioner prescribing data linked to the problem under management, and examined the characteristics of the GPs who prescribed opioids and the patients who received these prescriptions.

We analysed data from the Bettering the Evaluation and Care of Health (BEACH) program (detailed methods are described elsewhere3). For the period April 2010 to March 2011, we examined encounters at which opioids were either prescribed or supplied directly to patients. We then measured changes in opioid and oxycodone prescribing rates over the past decade and extrapolated these results to all Medicare GP service items claimed nationally.4 While Roxburgh and colleagues1 reported dispensing rates as measured by the Pharmaceutical Benefits Scheme (PBS), BEACH data measure GP prescription and supply actions. Using the international Anatomical Therapeutic Chemical classification,5 we defined opioids as “N02A” and oxycodone as “N02AA05”. We determined the statistical significance of differences by non-overlapping 95% CIs.

In the 2010–11 BEACH data year, at least one opioid was prescribed or supplied at 4666 of the 95 839 encounters (4.9%) recorded from 892 GPs (93.1% of the 958 GPs who participated in that year). There were a total of 5350 opioids prescribed (5237; 97.9%) or supplied (113; 2.1%) by the GP at the 4666 encounters. From this point, we shall refer to them all as being prescribed. Compared with encounters at which no opioids were recorded, those at which an opioid was prescribed were four times more likely to be claimable through workers compensation (6.8%; 95% CI, 5.7%–7.8% v 1.7%; 95% CI, 1.5%–1.9%), and more likely to be long or prolonged consultations (10.0%; 95% CI, 8.8%–11.2% v 7.8%, 95% CI, 7.2%–8.4%). Opioids were prescribed at a rate of 3.7 per 100 problems managed, accounting for 5.8% of all medications prescribed or supplied by participating GPs.

There was no significant difference in opioid prescribing rates for male and female patients. Opioid prescribing was rare for young patients, rose significantly for patients aged 25–44 years, peaked among 45–64-year-old patients and stayed almost as high in older age groups. Opioid prescribing was significantly less for patients new to the practice, possibly because of their younger age (results not shown) or GP reluctance to prescribe opioids at an initial consultation (Box 1). Commonwealth Health Care Card holders had a significantly higher rate of opioid prescribing than other patients; this rate was even higher than for patients aged 65 years and older, suggesting that age was not the only contributing factor.

While the prescribing rate for opioids did not differ with the age group of the GP, male GPs prescribed significantly more opioids per 100 encounters than did females (Box 2), adding to previous research evidence showing that female GPs prescribe fewer medications than males.6

Malignant neoplasms accounted for only 3.5% of opioids prescribed, and chronic non-cancer conditions for a further 43.9%, so a significant proportion were prescribed for conditions classed as non-chronic.7 Almost 60% of prescriptions were for musculoskeletal problems. The higher prescribing rate by male GPs may reflect their higher management rate of musculoskeletal problems when compared with female GPs.6 Back problems accounted for over a quarter of all opioids prescribed and was the most common individual problem for which opioids were provided. About one in 10 opioids prescribed were for osteoarthritis, provided at almost one in five occasions of osteoarthritis management. Less than 7% of opioids prescribed were for generalised multisite pain, but 72.7% of generalised multisite pain managements had an opioid prescribed (Box 2).

The most common opioids prescribed were combinations of paracetamol with at least 30 mg codeine (the minimum amount for classification as an opioid). Extrapolation suggests that there were over two million prescriptions for the year, nationally. The next most common opioid was oxycodone, followed by tramadol (Box 2).

Over the past decade, the total prescribing rate for total analgesics remained steady4 but the prescribing rate for opioids rose from 3.8 per 100 encounters in 2000–01 to 5.6 per 100 in 2010–11; this was particularly the case for oxycodone (up from 0.3 prescriptions per 100 encounters to 1.5 per 100 over the period). Extrapolation suggests GP prescriptions for opioids almost doubled (from 3.83 million to 6.65 million), while the number of oxycodone prescriptions increased almost sevenfold (from 0.26 million to 1.73 million). These increases reflect both the increased prescribing rate and the increase in the number of GP visits claimed through Medicare in recent years.

Our results show that Hall and Farrell were correct in their assertion that chronic non-malignant pain accounted for a far greater proportion of opioid prescriptions than did malignant neoplasms.2 However, we have also shown that a significant proportion of opioid prescriptions are for problems classified as non-chronic. The classification of a problem as non-chronic does not preclude it being chronic in some patients (although it is not usually chronic), nor does it preclude involvement of severe pain over an extended period.