Clinical drug investigation
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The mechanisms involved in the development of chronic pain are varied and complex. Pain processes are plastic and unrelieved pain may lead to changes in the neural structure involved in pain generation. Nociceptive pain announces the presence of a potentially damaging stimulus that occurs when noxious stimuli activate primary afferent neurons. ⋯ Response to drug treatment shows significant interindividual variability and can lead to side effects. The neurobiological mechanisms that cause pain may account for the different types of pain observed. Identification of these mechanisms may allow us to move from an empirical therapeutic approach to one that it is specifically targeted at the particular mechanisms of the type of pain experienced by an individual patient.
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Chronic pain is a major healthcare issue in Europe and globally, and inadequate or undertreated pain significantly reduces the ability of many patients to participate in ordinary daily activities, adversely affects their employment status and contributes to a substantial rate of depression and anxiety in patients with chronic pain. There is a broad distinction of chronic pain into chronic non-cancer pain and chronic cancer pain, and important subgroups of these include patients with rheumatic and/or orthopaedic diseases, pain syndromes caused by cancer itself and caused by cancer treatment. Despite comprising the majority of non-cancer pain in Europe, chronic non-cancer pain associated with rheumatic diseases and/or orthopaedic conditions is often inadequately managed. ⋯ The use of mild opioids, such as codeine and tramadol, and strong opioids, such as morphine, hydromorphone and oxycodone, may be appropriate where paracetamol and other non-opioid analgesics are ineffective in chronic non-cancer pain. Cancer pain, either related to the underlying disease or caused by cancer treatment, is also a common cause of chronic pain in the elderly. An understanding of individual needs is essential in providing adequate pain relief, which is a central goal of care in all patients with chronic pain.
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Chronic pain is a widespread public health issue that has many effects on physical, emotional and cognitive functions. An estimated 10-55% of all adults are thought to have chronic pain. Chronic pain is a multifactorial condition, caused by the complex interplay of nociceptive, neuropathic or mixed pathogenic mechanisms. ⋯ Adequate assessment of pain, using validated tools, is an essential prerequisite of successful pain management. Unidimensional scales are useful for the measurement of pain intensity, while multidimensional scales measure both pain intensity and the extent to which pain interferes with life activity and emotional functioning. Patients should be reassessed and followed up in order to monitor progress and measure improvements in pain.
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Opioids are the most powerful analgesic drugs currently available and consequently form an essential part of the treatment options for malignant and non-malignant chronic pain. However, the benefits of these medications can be offset by gastrointestinal adverse events such as nausea, vomiting and constipation, as well as adverse events affecting the CNS. These occur relatively frequently in patients receiving long-term opioids for pain relief and are a cause of additional patient suffering and reduced work and social functioning, measured as reductions in quality-of-life outcomes. ⋯ Estimated preference ratings, providing an insight into the trade-off between effective pain control and adverse events, have shown that utility decrements associated with an increase in adverse-event severity were similar in size to those caused by a shift from well controlled to poorly controlled pain. Given the rising prevalence of chronic pain conditions (affecting one in five adult Europeans), the direct and indirect costs incurred from the management of adverse events with long-term opioids are likely to be multiplied, contributing to the socioeconomic burden of chronic pain. For this reason, the adverse-event profile of opioid-based analgesics should be improved to achieve more efficient long-term pain control.
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Review
Pain treatment with opioids : achieving the minimal effective and the minimal interacting dose.
Appropriate and successful management of pain with opioid analgesics is based on tailoring pharmacologic treatment to the individual and identifying the minimal effective dose at which pain is controlled with minimal adverse effects. Morphine and morphine-like-agonists exhibit similar pharmacodynamic profiles, but substantially different receptor affinities and pharmacokinetic properties, which dictate the dosage, route and regimen required to achieve analgesic effect. Opioids exhibit differences in drug elimination resulting in marked variations in the plasma half-life value. ⋯ Dose titration is the key to successful therapy initiation with strong opioids in patients with moderate-to-severe pain. It is the only way to establish the optimal and minimal effective dose and provides the best protection against adverse effects. Committed physicians should adhere to guidelines on the appropriate use of opioids in all patients, particularly those with a high risk of adverse reactions.