Definition and Prevalence
Pain is a common symptom in palliative care. It can be present as a direct result of disease processes, for example in cancer, or can be the result of effects from treatment, such as radiation or surgery. A significant amount of research into the assessment and management of pain in a palliative care context is based on patients with cancer. Pain is a frequent complication of cancer, but it is also common in many other life-limiting illnesses. [11-13]
Pain is a significant symptom in many patients accessing palliative care services and recognising its presence can be a challenge for health care professionals. The prevalence of pain in advanced, metastatic or terminal cancer has been estimated at 66 per cent.  This is a similar rate as seriously ill patients in home care and those with lung disease. [14,15] The rates in HIV are higher at 50 to 80 per cent.  Pain is also the most common symptom experienced by paediatric palliative care patients.  While some patients with life limiting conditions may experience pain in the early stages of their condition,  it is certainly true that pain is a significant clinical feature for many patients at the end of life.  It is one of the most common symptoms in all life-limiting illnesses with one study reporting that over 50 per cent of patients with HIV, heart disease, COPD, renal failure and cancer experiencing pain.  While each non-malignant life-limiting disease has its own specific pathology and specific symptoms, pain remains one of the common symptoms to most life-limiting conditions. 
Pain that is not well controlled causes significant distress and disability, and despite the availability of best practice approaches to pain management,  there is wide variability in how pain is treated in practice.  The effective management of pain is therefore a core element of palliative care practice.
Identifying the type of pain the patient is experiencing is essential to guide the development of treatment plans and management options for patients. Certain conditions have a greater prevalence of neuropathic pain, for example, HIV,  and the assessment and management of neuropathic pain requires a unique approach. With the increasing complexity of cancer and other life-limiting illness treatments, and the longer survival of patients who have painful conditions, approaches which are holistic, multimodal, mechanism-based, and which start at diagnosis, are needed. [24,25]
In the palliative care setting, some of the important contributors to pain to consider and treat specifically are:
- Bone metastases and their complications including pathological fractures and spinal cord compression
- Malignant or non-healing wounds
- Neuropathic pain
- Radiotherapy / chemotherapy effects (usually short term)
- Depression / anxiety / fear
- Frailty, decreasing mobility or becoming bed-bound
- Constipation and urinary retention.
There are a large number of guidelines available to clinicians covering pain assessment and management. Some are written specifically for palliative care services, others are relevant as they focus on specific conditions, such as neuropathic pain or cancer pain, or specific patient groups, such as paediatrics or those living in residential care. These are discussed in more detail in the section on Pain Assessment.
Pain is a subjective, internal phenomenon and therefore can be influenced by a many internal and external factors. The biopsychosocial model of pain recognises the sensory, cognitive and social factors which contribute to the overall experience of pain.  A comprehensive approach to pain management begins at diagnosis, should be mechanism-based and multimodal, and must be tailored to the individual patient needs. The majority of pain in palliative care patients can be effectively treated with available medications and best practice management strategies, which includes regular assessment of pain with validated assessment tools. [17,27,28]
The World Health Organization (WHO) developed a three-step ladder model to support decision making in managing pain based on pain intensity. The model utilised a linear approach to pain with pharmacological treatments correlating from mild pain to severe pain. However, this model; does not recognise the role of non-pharmacological and interventional treatment options.  New approaches to treating pain are targeted at multimodal and individual treatments. 
Oral morphine, oxycodone and hydromorphone all have similar efficacy and toxicity in opioid naïve patients.  According to updated recommendations from the European Association of Palliative Care, any of these opioids can be used as first line opioids.  The use of simple analgesics or adjuvants may be useful to improve analgesic efficacy and reduce total opioid doses.  Non-pharmacological approaches to pain management can also contribute to an effective pain management plan and are often well accepted by patients.
Recent evidence-based guidelines for neuropathic pain suggest that two groups of medications may be used as first line adjuvant treatment – of the antidepressants, either tricyclics, or duloxetine or venlafaxine, and of the anticonvulsants, either gabapentin or pregabalin.  The evidence is weak for the use of opioids in neuropathic pain. 
The topics covered in the following pages will highlight the new approaches to assessing and treating pain. These topics are:
- Barriers to Pain Management
- Pain assessment
- Pharmacological Management - Opioid analgesics
- Pharmacological Management – Non-opioid analgesics
- Non-pharmacological approaches to pain management
- Radiotherapy and Interventional pain management.
Practice implications for pain assessment and management will vary according to condition and context of care and these are dealt with in detail in the corresponding sections.
The evidence for best practice pain management in palliative care continues to evolve. Much of the evidence about pain management comes from studies in populations potentially different from palliative care patients.  Studies of acute pain, single dose studies of particular analgesics, and studies in chronic non-malignant pain contribute to the evidence.
- The prevalence of pain in non-malignant life-limiting illness needs further investigation.
- Patients with non-malignant life limiting illnesses are more likely to not have their pain adequately assessed. 
- Recommendations about managing breakthrough pain are evolving. A consensus that breakthrough opioids need to be individually titrated, rather than provided in a fixed ratio to the background opioid, has emerged in the literature. 
- Subcutaneous or intravenous patient controlled analgesia devices used in the delivery of analgesics are being used more frequently outside the acute postoperative pain setting and may have a role in palliative care. 
- Further research is needed to identify the most effective pain assessment tools for use in palliative care  and to improve processes of routine care so that pain is managed most effectively.  Pain is being used in a number of studies to measure quality of life in both adults  and children palliative care patients. [38,39]
- Opioid rotation or switching and calculation of doses between various opioids in different populations and treatment settings is an important research area for palliative care. There is considerable variation in pharmacokinetics and pharmacodynamics of different opioids and between individual patients. The interactions of non-opioid medications may also cause alterations in pharmacokinetics. While some organisations have developed opioid dose equivalence tables there is a strong need for clinical decision making that is individually focused and opioid dosing titrated to the patient’s unique situation. [31,40-43]
- Research in the treatment of neuropathic pain is needed to strengthen the evidence base in palliative care. 
- The role of non-opioid analgesics and interventional pain management approaches remains poorly researched in the palliative care setting.
- The role of ‘Medicinal Cannabis’ remains controversial in palliative pain management. While public interest in its use has increased there remains low quality evidence for its addition to the pain management plan. [44-46]
- Palliative care services may now be caring for patients with a history of drug abuse and addiction or the risk of addiction and diversion. Guidelines are being developed to help clinicians and more research is needed to validate screening tools. 
- Evidence-based protocols and educational processes within institutions should be developed to improve the quality of care.