Dr Iain Lawrie and Dr Karen Simpson offer some background and simple advice for managing pain associated with musculoskeletal conditions.
The problem of musculoskeletal pain
Pain is the most common symptom that causes patients to seek the help of health professionals. Many seek advice and treatment for acute episodes of self-limiting pain, but many others experience ongoing discomfort. Approximately 50 per cent of those with chronic pain have musculoskeletal problems2. A small proportion of patients develop chronic pain syndromes. A recent European survey of over 46,000 householders suggested that 11 to 30 per cent had significant chronic pain. The healthcare costs of managing pain are significant3,4.
Musculoskeletal pain management
Initial treatment of acute pain is well known to both professionals and patients, with usual approaches being appropriate use of rest, physical measures, simple analgesics and anti-inflammatory medications. The symptoms that these patients experience usually improve within a few days or weeks and they do not routinely require specialist pain management.
Those who develop persisting musculoskeletal pain may be referred to specialist services. There are no commonly agreed recommendations for the management of most musculoskeletal pains, although there are guidelines for some, eg management of osteoarthritis5,6. Globally, back pain is another common disorder, affecting 10 per cent of the population7 and is one of the top ten most expensive healthcare problems.
There is a relative lack of knowledge about the pathophysiology of persistent musculoskeletal pain, a situation that may lead to patients often lacking information about their condition and its management. This can be a barrier to their active involvement in their own care and reduce their concordance with treatments8.
Management of musculoskeletal pain can be complex and no single approach will be adequate on its own. While pharmacotherapy remains the mainstay of treatment for many patients, other approaches such as physiotherapy, injection treatments, acupuncture, TENS, psychological/cognitive-behavioural therapies and structured rehabilitation programmes all have a role as part of a multidisciplinary strategy. However, this review will focus on pharmacological management.
Pharmacotherapy in musculoskeletal pain
The WHO analgesic ladder was developed for the management of pain associated with malignancy9, but many of its general principles can be applied to musculoskeletal pain.
Most patients referred to specialist pain management services will already have been prescribed simple analgesia, eg regular paracetamol and/or NSAIDs. Recent work has suggested that any analgesic benefit of paracetamol and NSAID combination therapy is small compared with treatment using either class of drug alone10. However, it is always useful to review patients’ use of such medication, as many will not have taken the drugs regularly and appropriately.
The problem of gastric, renal and anti-platelet side-effects in those taking NSAIDs is well known. The adverse findings regarding cardiovascular safety in prolonged use with the selective COX-2 inhibitors has had a significant impact for pain management services and patients. These issues have prompted a thorough review of NSAID use, and it would appear that there is some consensus that ‘traditional’, non-selective NSAIDs are all equally effective, with gastroprotective medication being appropriate for higher risk patients. There is a move away from long-term NSAIDs because of their toxicity, and the scene is set for increasing use of opioids, which may be less organ toxic.
Use of opioids
Physicians treating patients with chronic pain often debate the most appropriate patients and stage to use strong opioids in the treatment regimen. Most health professionals have no problems with prescribing weak opioids, eg codeine and dihydrocodeine, and preparations such as tramadol. The weak opioids are effective in managing moderate pain, especially when combined with simple analgesics, eg paracetamol. Tramadol has both opioid and non-opioid properties that interact synergistically11. It can lead to gastrointestinal problems or sedation and, for this reason, the more recent lower dose preparation of tramadol combined with paracetamol may be more appropriate in some patients.
The decision to prescribe strong opioids, such as morphine and its derivatives can be far more troublesome for health professionals, particularly in patients with persisting musculoskeletal pain. Some physicians avoid prescribing strong opioids due to concerns about addiction and side-effects12. However, it is important to prescribe according to the patient’s needs to achieve the primary goal, to manage their pain effectively. Concerns about tolerance, dependence and addiction are generally unfounded when opioids are used appropriately in the management of ongoing pain. However, a drug ‘holiday’ should be considered in patients taking long-term strong opioids for unspecified musculoskeletal pain as dependence and tolerance can become a problem. The physician should also monitor the patient for the degree of pain relief, side-effects and improvement in function and quality of life.
The evidence for the use of strong opioids in treating musculoskeletal pain is both limited and conflicting; more robust data is needed to underpin clinical practice. However, whilst opioids should only be considered after the use of other established therapies, clinical experience has shown some benefit in their use for persisting musculoskeletal pain. Opioids are effective both for nociceptive and neuropathic pain, and they also have anti-inflammatory properties13.
Prolonged-release preparations, such as morphine sulphate and oxycodone tablets, are preferable to short-acting drugs to achieve consistent analgesia. Opioid switching – substituting one opioid preparation for another – can be useful, as individuals differ in their response to different opioids. All strong opioids have the potential to cause gastrointestinal side-effects such as emesis and, more usually, constipation. Patients receiving strong opioids should usually also be prescribed a laxative.
Just as changing the type of opioid prescribed may be necessary in certain circumstances, so too may varying the method of delivery. Transdermal delivery (patch) systems are available for buprenorphine and fentanyl. Buprenorphine is available in some countries in a range of high- and low-dose formulations. The patch should be changed every three and seven days, respectively. Fentanyl has a range of high-dose patches, which should be changed every three days. A lower-dose 12µg/hour fentanyl patch is also available in some countries.
The starting dose for the high-dose patches can be too high for opioid naïve patients. The lower dose buprenorphine patch is available in three lower strengths and may be more suitable for patients who are sensitive to strong opioids. Transmucosal, oral and injectable opioids are rarely appropriate in this group of patients, as their use may lead to dose escalation and tolerance.
Use of adjunctive therapy
Adjunctive therapy plays a central role in the treatment of patients with pain related to malignancy, but its use in musculoskeletal pain is less widespread. Injury to deep tissues can cause both referred and neuropathic pain, and muscle spasm. Therefore, in some patients it may be appropriate to consider the use of adjunctive therapy such as anticonvulsants, antidepressants or muscle relaxants. The benefits and burdens of efficacy and side-effects should be considered in each case.