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Chronic pain and opioids: dispelling myths and exploring the facts

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Eileen Mann, BSc (Hons), RN, SCM, DPSN, PGCHE.

Nurse Consultant Pain Management, Institute of Health and Community Studies, Bournemouth University and Poole Hospital NHS Trust

This paper will explore the role of strong opioids for chronic non-malignant pain and the issues that arise in both acute and community settings. It will review some of the controversies and the paradoxes, explore the evidence that supports their use, as well as some of the undeniable pitfalls associated with strong opioid analgesia for patients, nurses and doctors, particularly within the primary care setting.
This paper will explore the role of strong opioids for chronic non-malignant pain and the issues that arise in both acute and community settings. It will review some of the controversies and the paradoxes, explore the evidence that supports their use, as well as some of the undeniable pitfalls associated with strong opioid analgesia for patients, nurses and doctors, particularly within the primary care setting.

Chronic non-malignant pain is a very common condition. Studies into its incidence within the community range from 7% through to 46.5% (Bowsher et al, 1991; Elliot et al, 1999). A more recent MORI poll conducted in 2001 suggests that almost one in four people in the UK suffer from chronic non-malignant pain, most commonly from arthritis and low back pain (MORI, 2001).

There is no doubt that chronic non-malignant pain can be much more difficult to treat than acute pain. However, we need to debunk the myths and misconceptions surrounding some of the most effective drugs available to us.

Pain and disability lead to escalating costs to humanity in terms of needless suffering. In a society where an ageing population prone to the development of chronically painful conditions is a reality, the fiscal implications related to pain-induced disability may eventually become unsustainable.

Despite increasing evidence published on the efficacy of opioids (McQuay, 1999; McQuay and Moore, 1998; Oxford Pain Research Trust, 2002) misunderstanding continues to surround their effective use. Inappropriate or excessive emphasis on potential side-effects can overshadow benefits (Carr, 2002). Over-burdensome bureaucracy impedes rapid and effective administration in clinical practice (Hawthorn and Redmond, 1998; Mann and Redwood, 2000; Carr, 2002) and lack of knowledge still hinders our effective use of these drugs (Ferrell et al, 2000). Most of the literature refers to the management of acute and predominantly postoperative pain in acute care settings and reflects the problems associated with the use of strong opioids. However, the issues and barriers that impede their effective use elsewhere, particularly for chronic non-malignant pain, can probably be applied just as easily. Despite some undeniable advances in the management of pain, that wonderful term 'opiophobia' described by Morgan (1985) is still alive and well and continues to assert a powerful influence.

What factors compromise opioid use?
Opioids are undeniably our most powerful analgesics, but equally undeniably politics, prejudice and our continuing ignorance impedes optimum prescribing (McQuay, 1999). Over 100 years ago opium poppies were grown on the Fens in Cambridgeshire to provide opium for working men, but the brewing lobby, concerned that opium would erode their market share, argued on thin evidence that alcohol was less dangerous (McQuay, 1999). Restrictions were eventually put on opioids worldwide and have undoubtedly ensured that their beneficial use has not been optimised.

Education for medical practitioners has been historically poor for pain management (Marcer and Deighton, 1988). For nurses it has not been any better, although it could be argued that nurses are the essential professionals in pain management. In fact nursing textbooks have traditionally contained limited content on pain. An analysis of nursing textbooks by Ferrell et al in 2000 indicated that pain accounted for only 0.5% of the total text in 50 books used in nursing education. Most had no information about the principles of addiction, tolerance and dependence or explored the barriers to pain management. The authors wisely urged publishers and editors to fill this void in books used by nurses.

In the absence of knowledge, fears and myths grow. Unfortunately, paradoxes in research can add to confusion and misinformation. For example, research results using opioids conducted in experimental settings on inflicted pain produce quite different results from opioids given to those in nociceptive (active tissue damage) pain (McQuay, 1999). Respiratory depression is seen readily in the pain-free experimental subject but is rare in those for whom pain serves as an antagonist to the drugs' respiratory depressive effects (Borgbjerg et al, 1996).

Opioid use is further compromised by the anxiety and concerns that surface when a rogue doctor such as Harold Shipman uses these drugs to kill patients. Shipman was jailed for life in 2000 for murdering 15 patients registered with his practice in Hyde, Greater Manchester. A subsequent inquiry decided that he was responsible for the deaths of at least 215 patients during his career.

Criminal exploitation of powerful opioids can do untold damage to public confidence. Even names such as diamorphine or heroin conjure up a negative public image. Government campaigns that warn 'Say no to drugs' may cloud the public's view and create the perception that all opioids are associated with the potential for great danger, with little emphasis on their therapeutic qualities. To finally compound the viewpoint, they are frequently seen as terminal-care drugs associated with death and the final painful stages of cancer.

While opioids to treat postoperative, trauma or cancer pain have long been accepted as appropriate in the western world, the concerns surrounding opioid use for chronic non-malignant pain are very real. Principal concerns of health-care professionals focus on the perception that they are ineffective in the long term, that their use will lead to a deterioration in the patient's condition or that their use will fuel addiction problems within society (Collett, 2001).

In addition, certain countries have a policy of scrutiny that can be triggered by regulatory agencies when opioids are used long term and this threat can deter their use (Clark and Sees, 1993). As stated by Gallagher (2002): 'Doctors are still faced with the personal and professional dilemma to withhold opioids (engage in torture) and expose the patient to the well-established deleterious consequences of untreated pain; or prescribe opioids and risk (hypothetically) consequences to the patient, such as addiction, risk of professional sanction or even criminal investigation.'

In some countries the very availability of opioids is problematic. Although these drugs are considered essential by the World Health Organization they are often poorly available in developing, as well as some developed countries, due to excessively strict narcotics laws, regulations and import quotas (Joranson et al, 2002).

Excellent work is currently being undertaken by the World Health Organization to endeavour to rectify this situation (WHO, 2000). In many countries, however, the reality is that patients with diseases such as HIV, AIDS and advanced cancer are still destined to die an unnecessarily painful death.

Fortunately, in the UK, we do not have rigorous import quotas or overly zealous scrutiny of opioid use to contend with. Whether the experience of the Harold Shipman case ever changes this is open to conjecture.

The UK has an ageing population where chronic non-malignant pain is an increasingly common complaint that appears to be still poorly understood or managed. Studies looking at the prescribing habits for chronic non-malignant pain among GPs (Turk et al, 1994) suggest relatively infrequent prescribing of opioids. Similar surveys of physician members of the Intractable Pain Society and the American Pain Society suggest that opioids are under-utilised and addiction is over-emphasised among those who do not specialise in pain management (Turk and Brody, 1992).

What are the goals of opioid use and what do we know so far?
Exploring the issues that support or dismiss the use of opioids for chronic non-malignant pain is not easy. As previously stated, we have good data now that indicates the efficacy of opioids in acute and cancer pain without relevant tolerance development, with easy-to-manage physical dependence and an insignificant risk of drug abuse (Schug et al, 2002).

Unfortunately, the situation is not so straightforward for chronic non-malignant pain and there are still many gaps in our knowledge and understanding. The issues that still need to be addressed are listed in Box 1.

Ineffective early pain management at a time when a potentially chronic pain can still be deemed acute can have damaging consequences (Hill, 1994; Celeri et al, 2000). The biopsychosocial model of pain continues to describe how the experience of uncontrolled acute pain can be indelibly imprinted upon our central nervous system, producing long-term changes and alterations to our finely balanced homeostasis at a biological and cellular level (Carr, 2002; Melzack, 1999). This enhances the imperative to use the drugs we currently have better and more efficiently in the early stages of painful trauma or disease. We should be following the evidence rather than suggesting nothing further can be offered or never risking the step up from weak and relatively ineffective opioids to a trial of strong ones.

What are the arguments against using opioids for chronic non-malignant pain?
If we accept that there is now good evidence that subjective pain perception can be reduced with opioids for certain types of chronic pain, what else must be achieved? It is generally recognised that just reducing pain, although a very real and important goal for patients, should not be the single aim of prescribing clinicians. Just reducing pain intensity can have a negative impact on patients if it is achieved at the cost of a poorer quality of life. Many patients, even when pain relief has been reported as significant, have dropped out of studies and discontinued opioid use for a variety of reasons related to side-effects or just a reluctance to continue the therapy (Kalso, 2002). Any pain relief achieved needs to be accompanied by an increase in functioning and activity, improved lifestyle and a decrease in perceived stress. Other factors that are usually studied and deemed significant include sleep pattern, fatigue, mood and side-effects. The risk of these drugs being diverted to those who use drugs for non-medical reasons must also be considered.

So far we have conflicting results on outcomes in terms of both physical functioning and activity or psychological functioning and cognitive impairment (Collett, 2001).

Rather than discounting the use of these drugs or leaving patients to languish on weak opioids such as codeine, dihydrocodeine or dextropropoxyphene, prescribing needs to become more evidence based.

Weak opioids, for so long the mainstay of analgesia, especially in the community, appear to provide little in the way of pain relief, but have a similar adverse side-effect profile to titrated doses of strong opioids (McQuay and Moore, 1998). On their own, weak opioids are consistently out-performed by both paracetamol and the non-steroidal anti-inflammatory drugs (NSAIDs) (McQuay and Moore, 1998; Oxford Pain Research Trust, 2002).

The benefits of opioids over non-opioids such as paracetamol and NSAIDs are often overlooked. Although paracetamol and NSAIDs are very effective (McQuay and Moore, 1998), there is ceiling to their analgesic effect.

Paracetamol is lethally toxic to the liver in doses not much larger than the standard therapeutic dose. NSAIDs have serious consequences in terms of adverse side-effects, especially in elderly people, and are estimated to cause the deaths of 2000 people a year in the UK alone (McQuay, 2002; Bandolier, 2002). The newer cyclo-ogygenase (COX) II inhibitors, initially thought to have a much better side-effect profile, are now under increasing scrutiny into their effects on the cardiovascular system (McQuay, 2002; Bandolier, 2002).

Conversely, there is scant evidence of serious consequences associated with the careful and experienced use of opioids for patients in pain. Although elderly people can be highly sensitive to strong opioids, long-term therapy is not associated with major organ toxicity (Kreek, 1973; Taub, 1982). Opioids come with a long list of potential side-effects such as respiratory depression, sedation, cognitive impairment, nausea, itching and constipation. However, some patients may sometimes become tolerant to these and side-effects can often be adequately controlled.

What are the risks of tolerance, dependence and addiction?
Opioids also have the potential to induce tolerance to their beneficial effect, cause physical dependence and addiction. Tolerance in this instance refers to the state of reduced responsiveness to the effects of a drug following previous administration. Similar to their administration for an acute pain, tolerance following chronic opioid use appears to be uncommon, with many patients stabilised on a long-term dose (Zenz et al, 1992).

Dependence is referred to as 'a state, psychic and sometimes also physical, resulting from the interaction between a living organism and a drug, characterised by behavioural and other responses that always include a compulsion to take the drug on a continuous or periodic basis in order to experience its physical effects and sometimes to avoid the discomfort of its absence' (WHO, 1969). More recently dependence has been characterised as psychological or physical dependence. Psychological dependence is the compulsion to continue to take a drug even with the knowledge that it is harmful. Physical dependence refers to the adaptive state of physical disturbance that can be induced when a drug is suddenly or rapidly withdrawn. Again careful management suggests the risk of physical dependence should not be used as a barrier to opioid use (Ralphs et al, 1994).

Addiction seems to be one of the principal reasons for excluding opioids from the management of chronic non-malignant pain. This risk, especially when evidence and our knowledge is still scant, appears to have been somewhat over-influential in prescribing habits. Although dated now, the major piece of work by Porter and Jick in 1980 suggested that addiction was rare in patients treated with opioids for pain. However, there are still major gaps in our understanding of addiction and its complex interplay with genetic risk, exposure and an adverse psychosocial environment. Current research links addiction to complex multiple neurotransmitter systems within the limbic system and related areas of the brain associated with reward, anxiety and the relief of depression (Kalso, 2002).

Can guidelines, contracts and algorithms help?
To improve and rationalise the use of strong opioids in primary care, the use of agreements or contracts with patients can offer a solution. These have been developed to provide a broad support structure of fully informed health professionals who monitor patients closely. The emphasis is on the importance of pain relief but is coupled to enhanced function via the active continuation of other therapy (Burchman and Pagel, 1995).

In the West experts are coming together to review current evidence and help practitioners identify patients who may be suitable for a trial of opioid therapy. These are then combined with further guidelines to suggest how this therapy may be managed effectively and with the fewest complications. Jamison et al (2002) suggests these can be successfully implemented although many physicians expressed a reluctance to consult algorithms when treating chronic pain.

The world wide web is enabling guidelines to be instantly accessed. So far the USA has produced Model Guidelines for the Use of Controlled Substances for the Treatment of Pain (Federation of State Medical Boards of the United States, 1998). In the UK, the Pain Society is producing a similar guideline or consensus document for use in this country (see Box 2).

We still have a long way to go to get it right but the picture on opioids is certainly looking clearer and help is out there to assist patients, clinicians and institutions to approach the use of opioids in a logical and evidence-based fashion. Although opioids should be only one part of a strategy to improve pain control, we need to ensure that those patients who may well derive benefit from their use are identified and managed in the best possible way.

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