Back pain can be subdivided into acute, subacute and chronic back pain. Back pain often begins with an episode of acute pain that can persist for a period of weeks. There may then follow a period of subacute pain persisting for weeks to months. Back pain that continues for three months is termed chronic back pain.
I. Acute phase
The causes of back pain are most often non-specific – leading to a functional disorder that may involve wear or damage, although often the exact aetiology of non-specific back pain is hard to determine. Specific, clearly identifiable causes of back pain, such as nerve root irritation or compression and inflammatory diseases, are less common.
Specific back pain is often associated with radiculopathy or spinal stenosis, but can also be associated with another specific spinal cause.
Chronic back pain can have nociceptive, neuropathic, inflammatory, and/or dysfunctional features1.
Pain can also be composed of two overlapping components – nociceptive and neuropathic parts – like for example in many forms of chronic back pain2.
Interestingly, the presence of neuropathic component is more frequent with increasing severity of chronic low back pain. In patients with mild pain intensity, neuropathic pain symptoms are clearly diagnosed in 16% of patients, while in patients with severe pain, this percentage increases up to more than 52%3.
Diagnosis and assessment of the patient presenting with back pain requires thorough and focused history-taking and physical examination to help place patients into three broad categories – those with non-specific pain, back pain associated with radiculopathy or spinal stenosis, or back pain potentially associated with another, specific spinal cause.
The diagnostic process must also ascertain how the back pain manifests physically and how it affects patient function.
Another key objectives in diagnosing back pain are to discover any physical causes that explain the complaint and, in so doing, to diagnose any serious or urgent pathology (red flags) requiring treatment. These include bone fractures, tumours, infections, and spinal crush injury.
A key element of the assessment of the patient presenting with back pain is to evaluate for psychosocial factors – or yellow flags – that are known to increase the risk for developing or perpetuating pain with an increased likelihood of long-term disability and work-loss due to back pain.
When taking a history, consider coexisting disease (cardio-respiratory disease, smoking, psychiatric diseases) and lifestyle habits (working conditions, social circumstances, and level of patient education).
Physical examination of the patient with back pain is a crucial element of diagnosis.
A combination of drugs with complementary pharmacokinetic profiles, or use of agents combining more than one analgesic mechanism of action, targets multiple pain pathways and offers the potential of synergy of effect.
Methods of combining drugs include use of single, loose-drug combinations and fixed combination preparations (formulated to contain two agents).
New analgesics with more than one mechanism of action in a single molecule offer the advantage of addressing different underlying mechanisms.
National Institute for Health and Clinical Excellence. 2009. http://www.nice.org.uk/nicemedia/live/11887/44334/44334.pdf
Paracetamol, NSAIDs, and cyclooxygenase inhibitors target the nociceptive component of chronic back pain but are largely ineffective on specific neuropathic pain mechanisms.
Opioid therapies target both nociceptive pain and, to a lesser extent, neuropathic pain, reflecting the fact that in chronic pain conditions the role of the opioidergic system in controlling pain perception is frequently reduced.
Agents that inhibit neurotransmitter uptake (e.g. antidepressants) target the neuropathic component of chronic back pain.
Anticonvulsant drugs (ion channel blockers) may offer some efficacy in managing chronic neuropathic back pain but are apparently not effective in nociceptive pain.
Other type of topical agents, like lidocaine plaster preparations, can be useful in managing localized neuropathic pain.
Newer agents like the MOR-NRI tapentadol combine two mechanisms of action, µ-opioid receptor agonism (MOR) and noradrenaline reuptake inhibition (NRI) in a single molecule.
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