Analgesic effects of nonsteroidal anti-inflammatory drugs in cancer pain due to somatic or visceral mechanisms

Non-steroidal anti-inflammatory drugs for pain in hospice/palliative care: an international pharmacovigilance study

OBJECTIVES

To describe the current, real-world use of non-steroidal anti-inflammatory drugs for pain and the associated benefits and harms.

METHODS

A prospective, multicentre, consecutive cohort pharmacovigilance study conducted at 14 sites across Australia, Aotearoa/New Zealand and the UK including hospital, hospice inpatient and outpatient services. Pain scores and harms were graded using the National Cancer Institute Common Terminology Criteria for Adverse Events at baseline, 2 days and 14 days. Ad-hoc safety reporting continued until day 28.

RESULTS

Data were collected from 92 patients between March 2018 and October 2021. Most patients had cancer (91%) and were coprescribed opioids (90%). At 14 days, 83% of patients had benefit from non-steroidal anti-inflammatory drugs and 22% had harm. The most common harms were nausea (8%), vomiting (3%), acute kidney injury (3%) and non-gastrointestinal bleeding (3%); only 2% were severe and no patients ceased their non-steroidal anti-inflammatory drugs due to toxicity. Overall, 65% had benefit without harm and 3% had harm without benefit.

CONCLUSIONS

Most patients benefited from non-steroidal anti-inflammatory drugs with only one in five patients experiencing tolerable harm. This suggests that short-term use of non-steroidal anti-inflammatory drugs in patients receiving palliative care is safer than previously thought and may be underused.

Management of pain in patients with bone metastases

Cancer-induced bone pain (CIBP) has a considerable impact on patients’ quality of life as well as physical and mental health. At present, patients with CIBP are managed according to the three-step analgesic therapy algorithm proposed by the World Health Organization. Opioids are commonly used as the first-line treatment for moderate-to-severe cancer pain but are limited due to addiction, nausea, vomiting and other gastrointestinal side effects. Moreover, opioids have a limited analgesic effect in some patients. In order to optimize the management of CIBP, we must first identify the underlying mechanisms. In some patients, surgery, or surgery combined with radiotherapy or radiofrequency ablation is the first step in the management of CIBP. Various clinical studies have shown that anti-nerve growth factor (NGF) antibodies, bisphosphonates, or RANKL inhibitors can reduce the incidence and improve the management of cancer pain. Herein, we review the mechanisms of cancer pain and potential therapeutic strategies to provide insights for optimizing the management of CIBP.

Pain Management in Breast Cancer Patients: A Multidisciplinary Approach

Pain is a significant problem and is one of the most invalidating symptoms in breast cancer (BC) patients that would negatively affect the functional status and the Quality of Life (QoL). Pain management in BC patients requires thorough patient evaluation and critical assessment of pain. The actual cause for the pain must be recognized, so management can be tailored to each patient. This review aims to discuss various treatment modalities employed for effectively managing pain in BC patients.

Pharmacotherapy makes up the cornerstone of the management of pain in BC patients. Both opioid and non-opioid analgesics are utilized. The WHO recommends a method called “by the ladder” for managing pain in BC patients where analgesics are used in ascending order. In comprehensive pain management (CPM), non-pharmacologic therapies are gaining wide acceptance and popularity, including complementary and alternative medicine (CAM), procedural and psychosocial interventions. Procedural interventions are usually used in case of severe pain refractory to pharmacological therapy. Techniques, such as radiotherapy, neurectomy, and nerve blocks, are effective in managing cancer pain. However, CAM therapies in BC pain management need to be guided by enough scientific evidence, decision-making, and medical judgment of regulatory bodies.

BC pain management is based on careful routine pain assessments and appropriate patient evaluation both physically and psychologically. Pain control is one of the methods to improve the QoL of BC patients. Both pharmacological and non-pharmacological therapies are accessible to patients today, but they should be used with caution to minimize toxicity and increase effectiveness. The use of any pain management intervention should be based on proper scientific evidence and collective medical judgment.

Self-medication practice with analgesics (NSAIDs and acetaminophen), and antibiotics among nursing undergraduates in University College Farasan Campus, Jazan University, KSA

OBJECTIVE

Self-medication practices are widely practiced globally as major form of self-care for pain management. Unfortunately, with COVID-19 pandemic, prescription only drugs are now increasingly being self-prescribed. Present study was therefore, conducted to generate data on self-medication practice with analgesics using non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen, and the antibiotics among nursing students of University College Farasan Campus.

MATERIALS AND METHODS

A cross-sectional descriptive study was conducted among 177 study participants (20±3 years) between December 2019 to February 2020 using questionnaire. Data analyses were done using origin software (6.1, Illinois, USA). Significance was considered at P<0.05. Study was conducted in Department of Nursing, University College Farasan Province, a premier educational institute of Farasan Island affiliated to Jazan university, KSA.

RESULTS

Self-medication practices were high among nursing students (n=154 participants, 87%). Acetaminophen was highest used drug for analgesic purposes without prescriptions (n=101 participants, 57%). Among NSAIDs, Ibuprofen was most preferred for various analgesic purposes (n=35 participants, 20%) followed by diclofenac (n=9 participants, 5%) and meloxicam (n=5 participants, 3%). Azithromycine was the only antibiotic used by participants (n=4 participant, 2%). Most common causes of self-medication were headache (45%), menstrual pain (23%) and fever (14%). Main reason for self-medications was lack of time to consult doctor (68%). Furthermore, self-medication was significantly associated with study year (P<0.003).

CONCLUSION

Results give rise to concern for general well-being of future nursing workforce. There is need to implement educational actions and awareness programmes to limit self-medication practices among educated youth of this beautiful Island.

Pain Management in Patients with Serious Illness

Managing pain in patients with serious illness can be complex. However, pain is often a prominent symptom in patients with malignant and nonmalignant serious illness and providers have to be adept at balancing effective pain management and safety. Clinicians should start with a standard pain assessment that lays important groundwork for developing a tailored multimodal approach to pain management. It is important to identify physical causes of pain and also existential causes. Opioids are not always appropriate but are still an important tool for managing pain. Basic opioid management and safe practices are essential when managing this population.

Effect of subcutaneous meloxicam on indicators of acute pain and distress after castration and branding in 2-mo-old beef calves1,2

The aim of this study was to assess knife castration and knife castration + branding in 2-mo-old calves, and the effect of a single dose of s.c. meloxicam at mitigating pain indicators. Seventy-one Angus crossbred bull calves (128 ± 18.5 kg of BW) were used in a 3 × 2 factorial design where main factors included procedure: sham (control calves, CT; n = 23), knife (KN; n = 24) or knife + branding (BK; n = 24), and medication: single s.c. administration of lactated ringer solution (NM; n = 35) or a single dose of 0.5 mg/kg of s.c. meloxicam (M; n = 36). Physiological samples were collected at T0, 60, 90, 120, and 180 min and on days 1, 2, 3, and 7 after procedure, whereas behavioral observations were evaluated at 2 to 4 h and 1, 2, 3, and 7 days after procedure. A procedure × time effect (P < 0.01) was observed for cortisol, where KN and BK calves had greater (P ≤ 0.01) cortisol concentrations than CT calves 60 min after the procedure, whereas BK calves had the greatest (P < 0.05) cortisol concentrations, followed by KN calves and by CT calves 90, 120, and 180 min after the procedure. A procedure × time effect (P = 0.01) was observed for tail flicks, where KN and BK calves had a greater (P < 0.05) number of tail flicks than CT calves on days 1 and 3, whereas BK calves had the greatest number of tail flicks, followed by KN calves, and then by CT calves on day 2. Haptoglobin had a procedure × medication × time interaction (P = 0.05), where BK-NM calves had greater haptoglobin concentrations than BK-M, KN-M, and CT calves on days 1 and 3, whereas BK-NM and KN-NM calves had greater haptoglobin concentrations than BK-M, KN-M, and CT calves on day 2 after the procedure. Lying duration and tail flicks had a medication effect (P = 0.04; P < 0.01) where M calves had greater (P < 0.05) lying duration and lower (P < 0.05) number of tail flicks than NM calves 2 to 4 h after procedure. No medication effects (P > 0.10) were observed for salivary cortisol, substance P, and scrotal temperature minutes after the procedure or for cortisol, substance P, serum amyloid-A, stride length, or behavioral observations days after the procedure. Overall, BK calves presented greater physiological and behavioral indicators of acute pain than KN calves, suggesting that the combination of knife castration + branding was more painful. Meloxicam administered s.c. was effective at reducing physiological and behavioral indicators of acute pain associated with knife castration and knife castration + branding.

Patterns of acute inflammatory symptoms prior to cancer diagnosis

Although many studies have examined the role of chronic inflammation in cancer development, few studies discuss the patterns of acute inflammation prior to cancer diagnosis. Patients with lung, colorectal, prostate, or breast cancer between 1 July 2006 and 31 December 2009 and their metastatic status at diagnosis were determined through the Swedish Cancer Register. Non-steroidal anti-inflammatory drugs (NSAIDs) use in the year prior to cancer diagnosis was assessed through the Swedish Prescribed Drug Register. There were 13,945 patients identified with breast cancer, 6501 with prostate cancer, 5508 with lung cancer, and 12,723 with colon cancer. For metastatic patients, there is strong evidence of higher NSAIDs use 1–3 months compared to 10–12 months prior to diagnosis (breast odds ratio (OR) = 3.54, 95% CI 2.26–5.54; prostate OR = 3.90, 95% CI 3.10–4.90; lung OR = 2.90 95% CI 2.44–3.44; colorectal OR = 1.67, 95% CI 1.36–2.05). For non-metastatic patients, increased NSAIDs use 1–3 months prior to diagnosis was also observed, but only to a smaller extent for lung and prostate cancer (prostate OR = 1.48, 95% CI 1.27–1.72; lung 1.41, 95% CI 1.19–1.67). In conclusion, if NSAIDs use reflects underlying inflammatory symptoms, there is support for the hypothesis that advanced cancer was associated with an acute inflammatory process.

Pediatric Oncology: Managing Pain at the End of Life

Pain is a common and highly distressing symptom in pediatric patients with advanced malignancies. Prompt recognition, assessment, and treatment of pain are necessary, especially at the end of life. Opioid medications remain the mainstay of treatment of malignant pain in children at the end of life and the amount of opioids required for adequate pain control in patients is highly variable. Nonpharmacological approaches including behavioral and physical approaches in addition to non-opioid pain medications should be used when possible to augment pain control. Identification and treatment of any underlying pathology is important and use of adjuvant medications based on pathophysiology and source of pain should be considered. In cases where adequate pain control is not achieved through these multiple modalities, an interdisciplinary approach including potential interventional techniques and alternative treatments is required. This multimodal approach to pain management is best provided by interdisciplinary teams, as these teams can best address the complex causes of pain and associated distress that occurs in patients and within families.

Drug management of visceral pain: concepts from basic research

Visceral pain is experienced by 40% of the population, and 28% of cancer patients suffer from pain arising from intra- abdominal metastasis or from treatment. Neuroanatomy of visceral nociception and neurotransmitters, receptors, and ion channels that modulate visceral pain are qualitatively or quantitatively different from those that modulate somatic and neuropathic pain. Visceral pain should be recognized as distinct pain phenotype. TRPV1, Na 1.8, and ASIC3 ion channels and peripheral kappa opioid receptors are important mediators of visceral pain. Mu agonists, gabapentinoids, and GABAB agonists reduce pain by binding to central receptors and channels. Combinations of analgesics and adjuvants in animal models have supra-additive antinociception and should be considered in clinical trials. This paper will discuss the neuroanatomy, receptors, ion channels, and neurotransmitters important to visceral pain and provide a basic science rationale for analgesic trials and management.

Symptom management in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) annually causes about one million deaths. Because of advanced stage at diagnosis, HCC carries a five-year survival rate of less than 5% in patients diagnosed with unresectable disease. Incidence for HCC is higher in men and individuals of Asian descent, where viral hepatitis, a leading cause of HCC, is endemic. This article will provide an overview of the complex symptom management of patients with HCC. The occurrence of multiple symptoms, including pain, fatigue, weight loss, and obstructive syndromes (e.g., ascites, jaundice) in patients with HCC is common. Because of limitations in the efficacy of current treatment options, aggressive symptom management is key to preserving physical functioning and quality of life in patients with HCC. A multidisciplinary team approach to symptom management of patients with HCC is critical, with oncology nurses playing an integral role.

Management of breakthrough pain in patients with cancer

Breakthrough pain (BTP) in patients with cancer lacks a consensus definition and is subsequently inadequately diagnosed and assessed, therefore making it more challenging to manage. Cancer pain is generally moderate to severe in intensity and persistent in nature. Despite the problematic definition of BTP, it is generally described as having similar intensity, but may also be transitory and variable in predictability. Most breakthrough analgesia fails to be effective in the time required for BTP. No useful analgesia is therefore provided but drug adverse effects escalate. Cancer pain management relies on the WHO analgesic ladder. The frequency of BTP and its inadequate management means that it has significant adverse effects on patients, their families and those involved in their care. This article outlines a systematic, clinical and evidence-based approach to managing BTP in patients with cancer that emphasizes a holistic approach and an understanding of multidimensional 'total pain'. Guidelines for managing BTP are presented and areas of developing research are identified.

Management strategies for pain in breast carcinoma patients: current opinions and future perspectives

Breast cancer is the most frequently encountered carcinoma in women worldwide. Pain is the most distressing symptom in patients with breast carcinoma and can occur at all stages of the disease due to the cancer per se as well as due to various diagnostic and treatment modalities. A proper pain assessment helps in identification of pain syndromes and guides in formulating analgesic strategies. Primary therapies of breast carcinoma like surgery, chemotherapy, and radiotherapy for bony metastases can cause substantial pain relief. However, multimodal analgesic approaches incorporating pharmacological, interventional as well as non-conventional techniques should be employed prior to, in conjunction with, and after primary therapies of breast cancer. The prevalence of chronic neuropathic pain following breast cancer surgery may exceed 50% by current estimates, and with the increase in life expectancy of these patients, providing adequate pain relief is of paramount importance to improve their quality of life. In this review, we discuss prevailing methods of evaluation and management of pain in patients of breast carcinoma and the new techniques that may become the mainstay of pain management protocols in future.

The rationale for a multimodal approach in the management of breakthrough cancer pain: a review

Breakthrough pain has been described differently in various countries, and not surprisingly, recommendations for its management vary according to the institution. Usually when breakthrough pain occurs, the patient's pain has already been managed according to the World Health Organization 3-step ladder for cancer pain. After this point, the treatment choice is usually based on clinical judgment, the physician's personal experience with interventional procedures, and local resources available. Opioids remain the mainstay of the management of breakthrough cancer pain. However, the combination of radio-oncology, adjuvant drugs, and interventional pain procedures can improve pain relief. This review addresses those questions and proposes a multimodal approach to manage breakthrough cancer pain.

Update in Cancer Pain Syndromes

Cancer pain assessment and management are integral to palliative medicine. This paper reviews recent publications in the period 1999-2004 in the broad categories of epidemiology, pain assessment, nonpharmacologic approaches to cancer pain (radiation therapy, anesthetic blocks, palliative surgery and chemotherapy, complementary and alternative medicine), and in nociceptive pain, neuropathic pain, visceral pain, and bone pain.

Double-blind evaluation of short-term analgesic efficacy of orally administered dexketoprofen trometamol and ketorolac in bone cancer pain

The analgesic efficacy and safety of dexketoprofen trometamol (the active enantiomer of the racemic compound ketoprofen) (25mg q.i.d.) vs. ketorolac (10mg q.i.d.) was assessed in 115 patients with bone cancer pain included in a multicenter, randomized, double-blind, parallel group study. A level of >/=40 mm on the 100 mm visual analog scale (VAS) and >/=10 in the pain rating index were required for inclusion. At the end of treatment on day 7 (+1 day), mean values of VAS were 32+/-24 mm for dexketoprofen and 40+/-30 mm for ketorolac (P=0.12) but the pain rating index was significantly lower in patients given dexketoprofen (8.5+/-2.3 vs. 9.7+/-2.9, P=0.04). Moreover, most of the patients reached a pain intensity difference from baseline >/=20 mm (75% of patients for dexketoprofen and 65% of patients for ketorolac). Around half of patients in both treatments had a pain intensity <30 mm on VAS at the end of treatment (55% for dexketoprofen and 47% for ketorolac). In the overall assessment of efficacy, a higher percentage of both patients and physicians rated dexketoprofen as 'quite effective' or 'very effective' compared to ketorolac. The percentage of patients withdrawn from the study for any reason as well as for insufficient therapeutic effect or due to adverse events was lower in the dexketoprofen group than in the ketorolac group. Treatment-related adverse events occurred in 16% of patients given dexketoprofen and in 24% given ketorolac. Serious adverse events occurred in 3.5% of patients from both groups but only one case of gastrointestinal hemorrhage was considered related to ketorolac. We conclude that dexketoprofen trometamol 25 mg q.i.d. oral route is a good analgesic therapy in the treatment of bone cancer pain, comparable to ketorolac 10 mg q.i.d., with a good tolerability profile.

Meloxicam and selective COX-2 inhibitors in the management of pain in the palliative care population

This paper discusses the treatment of pain in the palliative care patient, specifically the use of meloxicam and recent advances in agents with cyclooxygenase-2 (COX-2) selectivity. Meloxicam is a nonsteroidal anti-inflammatory drug (NSAID) that preferentially inhibits COX-2 more than cyclooxygenase-1 (COX-1), especially at low doses, thereby offering advantages over traditional nonselective NSAIDs. New COX-2 selective agents are discussed, including valdecoxib, parecoxib, etoricoxib, and COX-189.

Caring for children with advanced cancer integrating palliative care

The care of children with advanced cancer is multifaceted. Treatment should focus on continued efforts to control the underlying illness whenever possible. At the same time, children and their families should have access to interdisciplinary care aimed at promoting optimal physical, psychological and spiritual wellbeing. Open and compassionate communication can best facilitate meeting the goals of these children and families. However, there remain significant barriers to achieving optimal care related to lack of formal education, reimbursement issues and the emotional impact of caring for a dying child. Future research efforts should focus on ways to enhance communication, symptom management and quality of life for children with advanced cancer and their families. As efforts to break down barriers and create the evidence base continue, we conclude as follows: this is a most rewarding part of the practice of medicine. A kind word and caring attitude are remembered for decades.

A randomised controlled study on the use of anti-inflammatory drugs in patients with cancer pain on morphine therapy: effects on dose-escalation and a pharmacoeconomic analysis

The role of non-steroidal anti-inflammatory drugs (NSAIDs) in cancer pain has been well established in the treatment of mild pain and in association with opioids in the treatment of moderate to severe pain. The aim of this study was to verify the effects of NSAIDs on morphine escalation in advanced cancer patients with pain followed-up at home and to assess the pharmacoeconomic implications. A prospective randomised controlled study was carried out in 156 consecutive advanced cancer patients with pain followed-up at home in the period December 1999-December 2000. In this group of patients, 47 were selected with pain progression after 1 week of opioid stabilisation. Patients were randomly assigned to one of two groups: group 'O' patients were treated with continuing opioid escalation according to their clinical needs; group 'OK' received ketorolac 60 mg/daily orally (p.o.) in three doses and then continued opioid escalation according to their clinical situation. Performance status, doses of morphine before and after starting treatment, mean weekly pain intensity (assessed by means of a numerical scale from 0 to 10), mean weekly symptoms intensity, adverse effects and pain mechanisms were recorded. Moreover, drug costs per day in both groups were calculated. Patients who received ketorolac in addition to morphine showed a better analgesia after a week in comparison to the group treated with morphine only (P=0.005). Thereafter, morphine escalation was slower and the maximum morphine dose was lower in the group treated with ketorolac. The incidence and the severity of gastric discomfort was more evident in patients treated with ketorolac, while constipation was significantly increased in patients who received morphine only. Drug costs per day were similar in both groups; statistical differences were observed in patients who started on lower morphine doses (<100 mg/daily) in the two groups (4.3 in the ketorolac-morphine group versus 3.4 in the morphine group; P=0.012). The use of NSAIDs reduces the need for an opioid dose escalation or allows the use of lower doses. Their use is associated with a more intense gastric discomfort, but results in less opioid-related constipation. The eventual additive cost for NSAIDs therapy is negligible, especially in patients taking high doses of morphine.

Update on pain management for advanced genitourinary cancer

PURPOSE

Pain is a significant problem in many patients with genitourinary malignancy at all stages of disease. Optimal pain control becomes a primary concern as disease progresses and other therapies are exhausted. The selection of the most appropriate therapy becomes difficult without an understanding of the underlying mechanisms of pain and the available therapies.

MATERIALS AND METHODS

A review of the literature regarding the mechanisms and assessment of pain syndromes was performed. All available therapies were investigated with respect to conservative management with opioid medications and adjuvant drugs, and the indications for invasive techniques.

RESULTS

Increased understanding of the mechanisms and classification of pain syndromes has led to improved assessment and treatment. Despite these advances a significant number of patients have inadequate pain control and the education of treating physicians remains an important target for improving this situation.

CONCLUSIONS

Opioid medication is the mainstay of therapy in the majority of patients but with the appropriate addition of other adjuvant drugs patients may achieve optimal pain control without unwanted side effects. A few patients benefit from more invasive techniques, including plexus blocks and neuraxial infusion therapy, and the indications for these treatments are discussed. These therapies have largely superseded neuroablative procedures that are more destructive and associated with higher morbidity.

Advances in cancer pain management

Control of malignant pain and related symptoms is paramount to clinical success in caring for cancer patients. To achieve the best quality of life for patients and families, oncologists and palliative care clinicians must work together to understand problems related to psychologic, social, and spiritual pain. Pain is the primary problem targeted for control using the World Health Organization's (WHO) analgesic ladder. This article focuses on increased knowledge of analgesic action that may enable expansion of the WHO analgesic ladder to fulfill the broader objectives of palliative medicine. We discuss clinical experience with several classes of drugs that are currently used to treat cancer pain: 1) nonsteroidal anti-inflammatory drugs, with emphasis on cyclooxygenase-2 inhibitors; 2) opioid analgesics, with specific emphasis on methadone and its newly recognized value in cancer pain; 3) ketamine, an antagonist at N-methyl-d-aspartate receptors; and 4) bisphosphonates, used for pain resulting from bone metastases. New concepts that compare molecular actions of morphine at excitatory opioid receptors, and methadone at nonopioid receptor systems, are presented to underscore the importance of balancing central nervous system excitatory (anti-analgesic) versus inhibitory (analgesic) influences.

The use of anti-inflammatory drugs in cancer pain

The role of non-steroidal anti-inflammatory drugs (NSAIDs) in cancer pain has been well established in the treatment of mild pain and also alone or in association with opioids for the treatment of moderate to severe pain. Acutely, NSAIDs may be more than mild analgesics, and may provide additional analgesia when combined with opioids. However, NSAIDs have ceiling effects and there is no therapeutic gain from increasing dosages beyond those recommended. As there is no clearly superior NSAID, the choice should be based on experience and the toxicity profile that probably relates to the COX-1:COX-2 ratio. Among the older drugs, ibuprofen seems to have these properties.Non-steroidal anti-inflammatory drugs have been shown to have an opioid-sparing effect. Although the value of a simple narcotic-sparing effect may be questioned in cancer pain treatment, the use of NSAIDs may be useful when the increase in opioid dosage determine the occurrence of opioid toxicity. Like opioids, NSAIDs should not be considered analgesics for a specific type or cause of pain. There is a lack of evidence for any difference between different routes of NSAIDs administration. The long-term toxicity of NSAIDs in cancer pain is poorly defined due to a lack of studies. A variety of strategies have been used in an attempt to reduce the risks associated with NSAID therapy. Those NSAIDs that are weak COX-1 inhibitors may be preferred. In addition, concomitant administration of misoprostol is recommended in patients at increased risk for upper gastrointestinal complications.

Advances in cancer pain management

Control of malignant pain and related symptoms is paramount to clinical success in caring for cancer patients. To achieve the best quality of life for patients and families, oncologists and palliative care clinicians must work together to understand problems related to psychologic, social, and spiritual pain. Pain is the primary problem targeted for control using the World Health Organization's (WHO) analgesic ladder. This article focuses on increased knowledge of analgesic action that may enable expansion of the WHO analgesic ladder to fulfill the broader objectives of palliative medicine. We discuss clinical experience with several classes of drugs that are currently used to treat cancer pain: 1) nonsteroidal anti-inflammatory drugs (NSAIDs), with emphasis on cyclooxygenase-2 (COX-2) inhibitors; 2) opioid analgesics, with specific emphasis on methadone and its newly recognized value in cancer pain; 3) ketamine, an antagonist at N-methyl d-aspartate (NMDA) receptors; and 4) bisphosphonates, used for pain resulting from bone metastases. New concepts that compare molecular actions of morphine at excitatory opioid receptors, and methadone at non-opioid receptor systems, are presented to underscore the importance of balancing central nervous system excitatory (anti-analgesic) versus inhibitory (analgesic) influences.