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Key questions on chronic pain (1 CPD hour)

Dr Rosalind Adam answers questions on prescribing, initiating opiates, and complementary therapies

1. Could you offer any practical tips on common problems we may encounter when prescribing in chronic pain?

Chronic pain is pain that has persisted for three months or longer, although it is preferable to use the term ‘persistent pain’ with patients. It is important to take time to do a thorough assessment, particularly noting the nature of the pain and its impact on the individual, their mood and level of function – this will guide the management approach.

I frequently come across two problems with prescribing. First, patients (and doctors) can have unrealistic expectations of pharmacotherapies. What are the patients’ goals? It is unlikely that pharmacotherapy will be curative, especially in complex pain problems. We need to treat around five patients with peripheral neuropathic pain with pregabalin for one patient to experience a 50% reduction in their pain. The number needed to treat goes up to around 11 for pregabalin in fibromyalgia. Consider pharmacotherapy as one strategy in a holistic approach to rehabilitation.

Second, medication reviews can be suboptimal. We have a finite range of pharmacotherapies and it is important to assess and document response to each. Titrate to effective doses (it’s not uncommon to see patients stuck on initiation doses of neuropathic agents) and ask about adherence. Review and withdraw medications that aren’t providing acceptable benefits. If there has been no response to treatment with an adequate dose of a neuropathic painkiller within four weeks, there is unlikely to be a response thereafter.

2. What are the rules for initiating opiates and continuing prescriptions for chronic pain? What is the likelihood of addiction and tachyphylaxis? How can we manage these?

One of the difficulties we have with strong opioids is that evidence of long-term benefit is lacking. Few trials have assessed benefit beyond six months and most have high drop-out rates because of side-effects. We lack good long-term data on quality of life and functional outcomes but do know that opioids can cause significant short- and long-term side-effects and harm.

There are detailed guidelines on opioid initiation from the Scottish Intercollegiate Guidelines Network (SIGN), the British Pain Society (BPS), and the Royal College of Anaesthetists (RCOA), and a useful web resource from the Faculty of Pain Medicine.1 Patients with a nociceptive pain who have had some benefit from weak opioids are most likely to respond to strong opioids but a therapeutic trial is always necessary to establish whether opioids will be effective. The trial should have pre-defined goals (usually with respect to function as well as pain intensity) over a specific time period and a pre-agreed upper dose limit. Opioids should be stopped if there is lack of efficacy or rapid tolerance, and patients will require regular review, ideally with the same prescriber.

Aim for the lowest effective dose. My own experience is that those patients who are likely to respond to opioids do so at low doses and I suspect that we will see a move away from high-dose opioid prescribing for chronic pain. Doses above 120mg morphine equivalent in 24 hours are associated with increased risk of patient harm, usually without associated benefit. Specialist input should be sought for patients on high doses (generally between 120-180mg morphine equivalent in 24 hours). Remember to advise patients about DVLA driving regulations when initiating or adjusting opioids. Patients who continue on strong opioids should be reviewed at least annually.

Addiction and tachyphylaxis are difficult to quantify, but the RCOA reports that 8-12% of those prescribed opioids long term for chronic pain meet criteria for a current or past opioid use disorder. The misuse of prescription opioids is a major and growing problem in the US, where accidental overdose and mortality from prescribed opioids have increased dramatically over recent years. In the UK, the Office for National Statistics reports an underlying pattern of increasing deaths in which opioid pain medicine is mentioned on the death certificate as present. For those with addiction to prescribed opioids, a multidisciplinary approach is usually necessary and may involve the specialist pain team, addiction services and the psychiatry team if there are co-existing mental health problems.

3. GPs are encouraged to prescribe morphine rather than fentanyl, buprenorphine or oxycodone, but when might we use one of the others over morphine?

There is no clear evidence that any particular strong opioid is better than another in terms of efficacy for pain relief. It may be necessary to try more than one opioid sequentially if the patient experiences side-effects or if there is lack of efficacy with the first choice. Aim to establish the patient on a long-acting preparation without immediate release preparations. Oxycodone has more reliable bioavailability than morphine and can be useful if the patient experiences side-effects with morphine sulphate. Buprenorphine has low levels of active metabolite accumulation in those with renal impairment. Patches can be useful in stable pain and in those who have problems with the oral route or with absorption of oral medication and can be convenient for the patient. Patches are also difficult to misuse. However, I find that there are large steps between patch strength in terms of equivalent morphine dose, particularly with fentanyl, and have seen toxicity problems with both buprenorphine and fentanyl patches. 

How common is chronic pain, including pain for which no specific cause is found? How do the two groups of patients resemble and differ from each other?

Chronic pain affects approximately 20% of the population. Around 7% have pain that is intense, severely disabling and needs frequent medication. Those with chronic pain consult primary care five times more frequently than those without. The most frequent causes of pain in primary care are musculoskeletal disorders such as osteoarthritis and back or spinal pain. Fibromyalgia has a reported prevalence of between 0.5% and 5%.

All patients with chronic pain can experience a similar set of problems. Pain often co-exists with mood problems. There may be central neurophysiological reasons why low mood and pain co-exist, but persistent pain also interrupts sleep, employment and social and physical activities and reduces quality of life.

The medications we use to manage pain can add to symptom burden.

I consider chronic pain as a syndrome, and this helps me to take a systematic approach to tackling both pain and the interrelated problems.

Patients who have no obvious disease-related explanation for their pain can find it difficult to come to terms with pain and to self-manage. It is helpful to discuss the nature of pain. Patients with central sensitisation can often relate to ‘having the volume turned up’ on pain at a brain and nervous system level. It is helpful to stress that pain is serving no useful purpose and is not a marker of disease or physical damage. Giving patients permission to ignore pain and strategies for improving function in spite of a degree of pain are all parts of the rehabilitative process.

4. Does acupuncture work for particular types of patient? Does hypnosis have a role and if so, when and how? What about other complementary treatments such as Reiki and reflexology?

Acupuncture is a safe therapy that can provide short-term relief in patients with chronic low back pain and osteoarthritis, particularly of the knee. I am not aware of any good-quality studies that have evaluated the efficacy of hypnotherapy or Reiki for chronic pain. Persistent pain can have a profound effect on patient wellbeing and ability to relax. I do not discourage individuals from pursuing safe complementary approaches from a reputable practitioner if they are affordable to the patient and if they help with distraction or relaxation.

5. Which patients tend to benefit from pain management programmes (PMPs) and what are the main components of these programmes?

PMPs are intended for patients who have persistent pain with the interrelated problems already mentioned, such as difficulties participating in activities and reduced quality of life.

Most PMPs are performed in a group setting and are delivered by a multidisciplinary team, usually with physiotherapy and psychology input. PMPs tend to focus on changing patient behaviours, usually through guiding exercise and activity, pacing, goal-setting and identifying and challenging false or unhelpful beliefs about pain. The focus is on helping patients to live life as fully as possible with pain and to learn self-management principles.

6. What are the pros and cons of the drugs for neuropathic pain?

Neuropathic pain can be difficult to treat and doesn’t respond well to conventional analgesics. First-line medications include gabapentinoids (gabapentin and pregabalin) and tricyclic antidepressants. There is little to choose between these medications in terms of efficacy, but prescribing guidelines differ between England (NICE) and Scotland (SIGN). In Scotland, the Scottish Medicines Consortium restricts the use of pregabalin to adults with peripheral neuropathic pain in whom first- and second-line treatments have failed.

It is important to consider the underlying cause. Duloxetine is licensed for diabetic neuropathy and carbamazepine should be considered as first line for trigeminal neuralgia. Side-effect profiles will also influence prescribing. Gabapentinoids can cause dizziness, somnolence, gait disturbance, cognitive side-effects and weight gain. There is also increasing recognition that gabapentinoids have the potential for diversion and misuse, and this is an important consideration. The anticholinergic effects of tricyclic antidepressants can pose problems, especially in the elderly. We should also be mindful that patients with chronic pain are at increased risk of depression and suicide.

7. When would you consider interventions such as peripheral nerve stimulators and nerve blocks?

These types of intervention should be considered when there is a well-defined anatomical target as a source of nociception, such as a joint or nerve. I would consider minimally invasive interventions alongside other rehabilitation, for instance to provide sufficient relief to improve progress with physiotherapy and physical activity. Spinal cord stimulators are used in tertiary care. There is evidence that they can be of benefit in patients with ‘failed back surgery syndrome’ where other treatment strategies have failed.

8. Some patients ‘gain’ subconsciously or knowingly from their pain. Can we – and should we – identify and challenge this?

Pain is a subjective and complex experience that relies entirely on patient report and this can lead to challenges in the doctor-patient relationship. My own experience is that patients who ‘gain’ from their pain are a very small minority. It is always difficult to change behaviours. One aspect we can control is iatrogenic harm. I try to ensure continuity of care with a single doctor. Relieving pain is one of the core duties of a doctor and there can be a pressure to act at each consultation. For patients with complex pain problems it can be just as important to recognise when not to act – for example, to add or titrate a medication that would be more likely to increase problems in the long term.

9. What’s new on the horizon in chronic pain relief?

Advances in functional imaging have increased our understanding of the neurobiology of pain. Drugs that target specific ion channels involved in nociception are also being developed.

Studies are ongoing on safety and long-term effects of strong opioids in individuals with persistent pain.

On a practical level, models of service delivery are being reshaped to ensure all our resources are used effectively to assist patients with persistent pain. There are likely to be increasing roles for allied health professionals.

 

Dr Rosalind Adam is a GPSI in pain management in Aberdeen

Questions from Dr Melanie Wynne-Jones, a GP in Cheshire

 

Reference

  1. Opioids aware. A resource for patients and healthcare professsionals to support prescribing of opioid medicines for pain. tinyurl.com/fpm-opioids

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Readers' comments (1)

  • Chroni pain + opioids = chronic pain + opioid addiction

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