Pregabalin reduces pain in patients with chronic pancreatitis in a randomized, controlled trial

The pain of chronic pancreatitis: a persistent clinical challenge

The pain of chronic pancreatitis represents a major challenge to those working in the field, including pain specialists, gastroenterologists and surgeons. This article describes the different aetiologies of chronic pancreatitis and lists the models for the pathogenesis of pain, including novel ideas such as the role of the immune system in the modulation of pain. The patient profile in chronic pancreatitis is discussed along with the social impact of the disease in relation to alcohol misuse. The range of treatment strategies including medical, endoscopic and surgical approaches are evaluated. Common analgesic regimes and their limitations are reviewed. The pain of chronic pancreatitis remains refractory to effective treatment in many cases and further study and understanding of the underlying pathophysiology are required.

Pancreatic pain

PURPOSE OF REVIEW

Pain is the most common symptom of chronic pancreatitis, with a profound socioeconomic impact. Historical management paradigms failed, as they did not adequately address the fundamental underlying mechanisms. The present article describes the neurobiology of pain and sensitization in this condition, in an effort to explain prior failings and provide future directions for managing pain in chronic pancreatitis.

RECENT FINDINGS

A number of recent advances have been made in understanding the neurobiology of pain for this condition. This has been coupled with clinical advances in assessing sensitization to pain in these patients, which has been shown to predict response to medical and surgical therapy.

SUMMARY

Pain in chronic pancreatitis is complex. Addressing the mechanical and morphological findings in chronic pancreatitis without addressing the underlying neurobiological mechanisms is destined to fail. New advances in our understanding of the neurobiology of pain in chronic pancreatitis helps to explain prior failings and provides future direction for managing pain in patients afflicted by this disease.

Pregabalin and placebo responders show different effects on central pain processing in chronic pancreatitis patients

BACKGROUND

Pain control in chronic pancreatitis is a major challenge; the mechanisms behind analgesic treatment are poorly understood. This study aims to investigate the differences in pain sensitivity and modulation in chronic pancreatitis patients, based on their clinical response (responders vs nonresponders) to placebo or pregabalin treatment.

METHODS

This study was part of a randomized, double-blind, placebo-controlled trial evaluating the analgesic effects of pregabalin and placebo in chronic pancreatitis. Post hoc, patients were assigned to one of four groups, ie, responders and nonresponders to pregabalin (n=16; n=15) or placebo (n=12; n=17) treatment. Responders were defined as patients with >30% pain reduction after 3 weeks of treatment. We measured change in pain sensitivity before and after the treatment using electric pain detection thresholds (ePDT) in dermatomes C5 (generalized effects) and Ventral T10 (segmental effects). Descending endogenous pain modulation was quantified via conditioned pain modulation (CPM) paradigm.

RESULTS

Sixty patients were analyzed in a per-protocol analysis. ePDT change in C5 was significant vs baseline and greater in pregabalin (1.3 mA) vs placebo responders (-0.1 mA; P=0.015). This was not so for ePDT in Ventral T10. CPM increased more in pregabalin (9%) vs placebo responders (-17%; P<0.001). CPM changed significantly vs baseline only for pregabalin responders (P=0.006).

CONCLUSION

This hypothesis-generating study provides the first evidence that pain relief with pregabalin is associated with anti-hyperalgesic effects and increased endogenous inhibitory modulation. No such effects were observed in patients experiencing pain relief with the placebo treatment. The mechanisms underlying analgesic response to placebo vs drug treatments are different and, together with their interactions, deserve further study.

Systematic mechanism-orientated approach to chronic pancreatitis pain

Pain in chronic pancreatitis (CP) shows similarities with other visceral pain syndromes (i.e., inflammatory bowel disease and esophagitis), which should thus be managed in a similar fashion. Typical causes of CP pain include increased intrapancreatic pressure, pancreatic inflammation and pancreatic/extrapancreatic complications. Unfortunately, CP pain continues to be a major clinical challenge. It is recognized that ongoing pain may induce altered central pain processing, e.g., central sensitization or pro-nociceptive pain modulation. When this is present conventional pain treatment targeting the nociceptive focus, e.g., opioid analgesia or surgical/endoscopic intervention, often fails even if technically successful. If central nervous system pain processing is altered, specific treatment targeting these changes should be instituted (e.g., gabapentinoids, ketamine or tricyclic antidepressants). Suitable tools are now available to make altered central processing visible, including quantitative sensory testing, electroencephalograpy and (functional) magnetic resonance imaging. These techniques are potentially clinically useful diagnostic tools to analyze central pain processing and thus define optimum management approaches for pain in CP and other visceral pain syndromes. The present review proposes a systematic mechanism-orientated approach to pain management in CP based on a holistic view of the mechanisms involved. Future research should address the circumstances under which central nervous system pain processing changes in CP, and how this is influenced by ongoing nociceptive input and therapies. Thus we hope to predict which patients are at risk for developing chronic pain or not responding to therapy, leading to improved treatment of chronic pain in CP and other visceral pain disorders.

Pregabalin for chronic pain: does one medication fit all?

BACKGROUND

Pregabalin is frequently prescribed for chronic non-cancer pain. No previous study has examined its off-label use.

OBJECTIVES

Our primary aim was to assess the proportion of patients taking pregabalin for conditions approved by Health Canada ('on-label') and compare their perspectives on its use to those who use pregabalin for other conditions ('off-label').

METHODS

Patients who have used pregabalin within the past year were recruited from two registries of chronic non-cancer pain patients treated in tertiary care clinics: the Quebec Pain Registry and the Fibromyalgia Patients Registry. Data on the use of pregabalin and its perceived benefits were collected from the registries and from completed questionnaires.

RESULTS

Out of 4339 screened chronic non-cancer pain patients, 355 (8.18%) met the study selection criteria. Three-quarters of them (268/355) used pregabalin for pain conditions not approved by Health Canada and were therefore regarded as off-label users. The most prevalent condition for pregabalin use was lumbar back pain (103/357; 28.85%). There were no significant differences between on- and off-label users in their perceived satisfaction from pregabalin therapy and its effect on function and quality of life. Among former users, the most prevalent reason for discontinuation was adverse effects, mainly dry mouth and weight gain.

CONCLUSIONS

We conclude that despite specific indications for pregabalin prescription, it is mainly used off-label, notably for low back pain. Nevertheless, off-label users were equally satisfied with its clinical effects. Although formal exploration of the broader analgesic properties of pregabalin is warranted, treating heterogeneous chronic pain conditions with pregabalin may be legitimate.

LIMITATIONS

The main limitations of the study are patients' low response rate, the recruitment of participants solely from a tertiary pain center and not from the general patient population and a possible recall bias that may have arisen from the retrospective nature of the study.

Chronic pancreatitis

PURPOSE OF REVIEW

We review selected important clinical observations in chronic pancreatitis reported in 2013.

RECENT FINDINGS

Early diagnosis of chronic pancreatitis remains difficult, although newer techniques utilizing endoscopic ultrasonography-elastography and MRI hold promise. Patients with chronic pancreatitis are at risk of nutritional deficiencies. Osteoporosis, osteopenia, and bone fracture are particularly common in these patients, and require active intervention and treatment. Diabetes caused by chronic pancreatitis, type 3c diabetes, has specific characteristics and requires careful management. Antioxidants and neuromodulators may decrease pain in some patients with chronic pancreatitis. Endoscopic treatment is effective and can be utilized in patients with painful chronic pancreatitis, although randomized trials demonstrate that surgical therapy is somewhat more durable and effective. Although surgery has typically been a last resort, some advocate early surgical intervention but the optimal time remains unknown.

SUMMARY

Early diagnosis of pancreatitis may be improved by newer techniques associated with endoscopic ultrasonography imaging. Treatment of nutritional deficiencies and diabetes is an important aspect of treating chronic pancreatitis. Pain relief with adjunct means of pain modulation should be tried before starting narcotics for pain control. Endoscopic therapy is appropriate for treating chronic pancreatitis and its local complications and surgical intervention can be considered early in carefully selected individuals.

Treatment options for chronic pancreatitis

This Review covers the latest developments in the treatment options for chronic pancreatitis. Pain is the most frequent and dominant symptom in patients with chronic pancreatitis, which ranges from severe disabling continuous pain to mild pain attacks and pain-free periods. Conventional treatment strategies and recent changes in the treatment of pain in patients with chronic pancreatitis are outlined. The different treatment options for pain consist of medical therapy, endoscopy or surgery. Their related merits and drawbacks are discussed. Finally, novel insights in the field of genetics and microbiota are summarized, and future perspectives are discussed.

[Pain management in chronic pancreatitis and chronic inflammatory bowel diseases]

Apart from local inflammation and defects in secretion, central mechanisms are important for pain etiology in chronic pancreatitis. Therefore, centrally acting co-analgetic agents can be used in addition to classical pain medications. Endoscopic interventions are preferred in patients with obvious dilation of the pancreatic duct. Surgical interventions are generally more effective although they are usually reserved for patients with prior failure of conservative treatment. Diverse surgical options with different efficacies and morbidities are used in individual patients.One of the main problems in chronic inflammatory bowel diseases is abdominal pain. Primarily the underlying disease needs to be adequately treated. Symptomatic pain management will most likely include treatment with acetaminophen and tramadol as well as occasionally principles of a multimodal pain regimen. For the treatment of arthralgia as well as enteropathy-associated arthritis the same treatment options are available as for other spondyloarthritic disorders.

Treatment options in painful chronic pancreatitis: a systematic review

BACKGROUND

Longlasting and unbearable pain is the most common and striking symptom of chronic pancreatitis. Accordingly, pain relief and improvement in patients' quality of life are the primary goals in the treatment of this disease. This systematic review aims to summarize the available data on treatment options.

METHODS

A systematic search of MEDLINE/PubMed and the Cochrane Library was performed according to the PRISMA statement for reporting systematic reviews and meta-analysis. The search was limited to randomized controlled trials and meta-analyses. Reference lists were then hand-searched for additional relevant titles. The results obtained were examined individually by two independent investigators for further selection and data extraction.

RESULTS

A total of 416 abstracts were reviewed, of which 367 were excluded because they were obviously irrelevant or represented overlapping studies. Consequently, 49 full-text articles were systematically reviewed.

CONCLUSIONS

First-line medical options include the provision of pain medication, adjunctive agents and pancreatic enzymes, and abstinence from alcohol and tobacco. If medical treatment fails, endoscopic treatment offers pain relief in the majority of patients in the short term. However, current data suggest that surgical treatment seems to be superior to endoscopic intervention because it is significantly more effective and, especially, lasts longer.

Spectrum of use and effectiveness of endoscopic and surgical therapies for chronic pancreatitis in the United States

OBJECTIVE

This study aims to describe the frequency of use and reported effectiveness of endoscopic and surgical therapies in patients with chronic pancreatitis treated at US referral centers.

METHODS

Five hundred fifteen patients were enrolled prospectively in the North American Pancreatitis Study 2, where patients and treating physicians reported previous therapeutic interventions and their perceived effectiveness. We evaluated the frequency and effectiveness of endoscopic (biliary or pancreatic sphincterotomy, biliary or pancreatic stent placement) and surgical (pancreatic cyst removal, pancreatic drainage procedure, pancreatic resection, surgical sphincterotomy) therapies.

RESULTS

Biliary and/or pancreatic sphincterotomy (42%) were the most common endoscopic procedure (biliary stent, 14%; pancreatic stent, 36%; P < 0.001). Endoscopic procedures were equally effective (biliary sphincterotomy, 40.0%; biliary stent, 40.8%; pancreatic stent, 47.0%; P = 0.34). On multivariable analysis, the presence of abdominal pain (odds ratio, 1.82; 95% confidence interval, 1.15-2.88) predicted endoscopy, whereas exocrine insufficiency (odds ratio, 0.63; 95% confidence interval, 0.42-0.94) deterred endoscopy. Surgical therapies were attempted equally (cyst removal, 7%; drainage procedure, 10%; resection procedure, 12%) except for surgical sphincteroplasty (4%; P < 0.001). Surgical sphincteroplasty was the least effective (46%; P < 0.001) versus cyst removal (76% drainage [71%] and resection [73%]).

CONCLUSIONS

Although surgical therapies were performed less frequently than endoscopic therapies, they were more often reported to be effective.

An overview of the diagnosis and management of nutrition in chronic pancreatitis

Chronic pancreatitis is characterized by long-standing inflammation of the pancreas, which results in fibrosis and the gradual loss of pancreatic function. The loss of islets and acinar cells results in diabetes and exocrine insufficiency, respectively. Exocrine insufficiency can result in maldigestion of fat, protein, and carbohydrate as well as vitamins and minerals. Patients may present with variable severity of disease, from mild to severe. The diagnosis of chronic pancreatitis can be challenging, especially in patients with early or mild disease who have few to no morphologic abnormalities on standard abdominal imaging studies. A number of imaging modalities and tests have evolved to aid in the diagnosis of chronic pancreatitis based on changes in structure or function. Clinicians typically focus on treating pain in chronic pancreatitis as opposed to exocrine insufficiency, despite the fact that maldigestion and malabsorption can result in nutrition deficiencies. The aims of this review are to describe the various modalities used to diagnose chronic pancreatitis, to illustrate the nutrition deficiencies associated with exocrine insufficiency, and to provide an overview of nutrition assessment and treatment in these patients.

Altered central pain processing after pancreatic surgery for chronic pancreatitis

BACKGROUND

Chronic abdominal pain is common in chronic pancreatitis (CP) and may involve altered central pain processing. This study evaluated the relationship between pain processing and pain outcome after pancreatic duct decompression and/or pancreatic resection in patients with CP.

METHODS

Patients with CP underwent quantitative sensory testing. Pain processing was measured via electrical pain detection (ePDT) and electrical pain tolerance (ePTT) thresholds in dermatomes C5 and L4. Inhibitory descending pain control mechanisms were assessed using the conditioned pain modulation (CPM) paradigm. Healthy controls and patients with CP were compared, and patients with CP and a poor pain outcome (visual analogue scale (VAS) score greater than 30) were compared with those with a good pain outcome (VAS score 30 or less).

RESULTS

Forty-eight patients with CP had lower ePDT, ePTT and CPM responses compared with values in 15 healthy controls (P < 0·030). The sum of ePDT values was lower in patients with a poor pain outcome than in those with a good outcome (median 7·1 versus 11·2 mA; P = 0·008). There was a correlation with the VAS score and the sum of ePDT values (rs  = -0·45, P = 0·016) and ePTT values (rs  = -0·46, P = 0·011), and CPM response (rs  = -0·43, P = 0·006) in patients with CP.

CONCLUSION

After pain-relieving pancreatic surgery, patients with CP exhibit altered central pain processing compared with that in healthy controls. Poor pain outcomes are associated with more central sensitization and more pronociceptive descending pain modulation, and this should be considered when managing persistent pain after pain-relieving surgery for CP.

Pharmacological pain management in chronic pancreatitis

Intense abdominal pain is a prominent feature of chronic pancreatitis and its treatment remains a major clinical challenge. Basic studies of pancreatic nerves and experimental human pain research have provided evidence that pain processing is abnormal in these patients and in many cases resembles that seen in neuropathic and chronic pain disorders. An important ultimate outcome of such aberrant pain processing is that once the disease has advanced and the pathophysiological processes are firmly established, the generation of pain can become self-perpetuating and independent of the initial peripheral nociceptive drive. Consequently, the management of pain by traditional methods based on nociceptive deafferentation (e.g., surgery and visceral nerve blockade) becomes difficult and often ineffective. This novel and improved understanding of pain aetiology requires a paradigm shift in pain management of chronic pancreatitis. Modern mechanism based pain treatments taking into account altered pain processing are likely to increasingly replace invasive therapies targeting the nociceptive source, which should be reserved for special and carefully selected cases. In this review, we offer an overview of the current available pharmacological options for pain management in chronic pancreatitis. In addition, future options for pain management are discussed with special emphasis on personalized pain medicine and multidisciplinarity.

Pain in chronic pancreatitis: Managing beyond the pancreatic duct

Chronic pancreatitis (CP) continues to be a clinical challenge. Persistent or recurrent abdominal pain is the most compelling symptom that drives patients to seek medical care. Unfortunately, in spite of using several treatment approaches in the clinical setting, there is no single specific treatment modality that can be earmarked as a cure for this disease. Traditionally, ductal hypertension has been associated with causation of pain in CP; and patients are often subjected to endotherapy and surgery with a goal to decompress the pancreatic duct. Recent studies on humans (clinical and laboratory based) and experimental models have put forward several mechanisms, including neuroimmune alterations, which could be responsible for pain. This might explain the partial or no response to single modality treatment in a significant proportion of patients. The current review discusses the recent concepts of pain generation in CP and evidence based therapeutic approaches (other than ductal decompression) to handle persistent or recurrent pain. We focus primarily on parenchymal and neural components; and discuss the role of antioxidants and the existing controversies, drugs that interfere with neural transmission, pancreatic enzyme supplementation, celiac neurolysis, and pancreatic resection procedures. The review concludes with the treatment approach that we follow at our institute.

Reliability of static and dynamic quantitative sensory testing in patients with painful chronic pancreatitis

BACKGROUND AND OBJECTIVES

Quantitative sensory testing (QST) has proven to be an important instrument to characterize mechanisms underlying somatic and neuropathic pain disorders. However, its reliability has not previously been established in patients with visceral pain. We investigated the test-retest reliability of static and dynamic QST in patients with visceral pain due to chronic pancreatitis.

METHODS

Sixty-two patients (38 men, 53 [11] y) with painful chronic pancreatitis were included. Static QST comprised sensory thresholds for pressure and electrical stimulation performed in the ventral and dorsal T10 dermatomes (sharing spinal innervation with the pancreas, ie, pancreatic viscerotomes) and in 4 heterologous regions (control areas). Dynamic QST comprised conditioned pain modulation. Measurements were obtained from 2 subsequent test sessions separated by 1 week.

RESULTS

The reliability of static QST was generally high, with the best test-retest performance seen for pressure pain thresholds (intraclass correlation coefficients [ICC], 0.74) and electrical sensation thresholds (ICC, 0.66). In contrast, the reliability of dynamic QST was poor (ICC, 0.01). For static QST measures, the reliability was higher for pain thresholds compared with suprapain thresholds (P < 0.01). No differences between assessments in the pancreatic viscerotomes compared with heterologous regions were seen (P = 0.6).

CONCLUSIONS

Sensory thresholds in the pancreatic viscerotomes and control areas were reproducible over time. In contrast, dynamic QST measurements reflecting active central modulation of pain processing state (ie, conditioned pain modulation) were not stable over time and showed considerable variability. These factors should be taken into consideration in case QST is used to follow disease mechanisms, drug effects, or effects of pain intervention.

Management of chronic pancreatitis

Advances in our understanding of chronic pancreatitis have improved our care of patients with this disease. Although our therapies are imperfect and many patients remain symptomatic, appropriate medical care improves the quality of life in these patients. Proper management requires an accurate diagnosis, recognition of the modifiable causes of disease, assessment of symptoms and complications, treatment of these symptoms and complications utilizing a multidisciplinary team, and ongoing monitoring for the effect of therapy and the occurrence of complications.

Management for pancreatolithiasis: a Japanese multicenter study

OBJECTIVES

A Japanese multicenter study of pancreatolithiasis was performed to investigate its clinical features and determine treatment strategies for pancreatolithiasis.

METHODS

A retrospective study was performed on 916 patients managed in 34 institutions for a period of more than 5 years.

RESULTS

The treatment methods were extracorporeal shock wave lithotripsy (ESWL) in 479 patients, surgery in 133, and endoscopy alone in 68. Fragmentation of stones after ESWL was achieved in 92.4% of the patients. However, complete stone clearance was achieved in 49.4% of the patients after ESWL alone. The complete stone clearance rate was lower after ESWL than after endoscopy (87.9%). The incidence of early complications was significantly higher after surgery (13.3%) than after ESWL (6.1%). The frequencies of total stone recurrence after ESWL (22.5%) and endoscopy (12.0%) were significantly higher than that after surgery (1.5%). After ESWL (17.6%), abdominal pain recurred significantly more frequently than after surgery (2.2%). Stones and abdominal pain most often recurred within 3 years after ESWL and endoscopy.

CONCLUSIONS

First-line treatment of pancreatic stones should be ESWL alone or with endoscopy because of its minimal invasiveness and low incidence of early complications. Surgery should be performed on patients in whom ESWL and endoscopy failed.

Quantitative sensory testing predicts pregabalin efficacy in painful chronic pancreatitis

BACKGROUND

A major problem in pain medicine is the lack of knowledge about which treatment suits a specific patient. We tested the ability of quantitative sensory testing to predict the analgesic effect of pregabalin and placebo in patients with chronic pancreatitis.

METHODS

Sixty-four patients with painful chronic pancreatitis received pregabalin (150-300 mg BID) or matching placebo for three consecutive weeks. Analgesic effect was documented in a pain diary based on a visual analogue scale. Responders were defined as patients with a reduction in clinical pain score of 30% or more after three weeks of study treatment compared to baseline recordings. Prior to study medication, pain thresholds to electric skin and pressure stimulation were measured in dermatomes T10 (pancreatic area) and C5 (control area). To eliminate inter-subject differences in absolute pain thresholds an index of sensitivity between stimulation areas was determined (ratio of pain detection thresholds in pancreatic versus control area, ePDT ratio). Pain modulation was recorded by a conditioned pain modulation paradigm. A support vector machine was used to screen sensory parameters for their predictive power of pregabalin efficacy.

RESULTS

The pregabalin responders group was hypersensitive to electric tetanic stimulation of the pancreatic area (ePDT ratio 1.2 (0.9-1.3)) compared to non-responders group (ePDT ratio: 1.6 (1.5-2.0)) (P = 0.001). The electrical pain detection ratio was predictive for pregabalin effect with a classification accuracy of 83.9% (P = 0.007). The corresponding sensitivity was 87.5% and specificity was 80.0%. No other parameters were predictive of pregabalin or placebo efficacy.

CONCLUSIONS

The present study provides first evidence that quantitative sensory testing predicts the analgesic effect of pregabalin in patients with painful chronic pancreatitis. The method can be used to tailor pain medication based on patient's individual sensory profile and thus comprises a significant step towards personalized pain medicine.

Quantitative sensory testing predicts pregabalin efficacy in painful chronic pancreatitis

BACKGROUND

A major problem in pain medicine is the lack of knowledge about which treatment suits a specific patient. We tested the ability of quantitative sensory testing to predict the analgesic effect of pregabalin and placebo in patients with chronic pancreatitis.

METHODS

Sixty-four patients with painful chronic pancreatitis received pregabalin (150-300 mg BID) or matching placebo for three consecutive weeks. Analgesic effect was documented in a pain diary based on a visual analogue scale. Responders were defined as patients with a reduction in clinical pain score of 30% or more after three weeks of study treatment compared to baseline recordings. Prior to study medication, pain thresholds to electric skin and pressure stimulation were measured in dermatomes T10 (pancreatic area) and C5 (control area). To eliminate inter-subject differences in absolute pain thresholds an index of sensitivity between stimulation areas was determined (ratio of pain detection thresholds in pancreatic versus control area, ePDT ratio). Pain modulation was recorded by a conditioned pain modulation paradigm. A support vector machine was used to screen sensory parameters for their predictive power of pregabalin efficacy.

RESULTS

The pregabalin responders group was hypersensitive to electric tetanic stimulation of the pancreatic area (ePDT ratio 1.2 (0.9-1.3)) compared to non-responders group (ePDT ratio: 1.6 (1.5-2.0)) (P = 0.001). The electrical pain detection ratio was predictive for pregabalin effect with a classification accuracy of 83.9% (P = 0.007). The corresponding sensitivity was 87.5% and specificity was 80.0%. No other parameters were predictive of pregabalin or placebo efficacy.

CONCLUSIONS

The present study provides first evidence that quantitative sensory testing predicts the analgesic effect of pregabalin in patients with painful chronic pancreatitis. The method can be used to tailor pain medication based on patient's individual sensory profile and thus comprises a significant step towards personalized pain medicine.

Is altered central pain processing related to disease stage in chronic pancreatitis patients with pain? An exploratory study

Background

The most dominant feature in chronic pancreatitis is intense abdominal pain. Changes in spinal and/or supraspinal central nervous system pain processing due to visceral nociceptive input play an important role in this pain. How altered pain processing is related to disease stage still needs study.

Methodology/Principal Findings

Sixty chronic pancreatitis patients were compared to 15 healthy controls. Two subgroups of pancreatitis patients were defined based on the M-ANNHEIM severity index of chronic pancreatitis; i.e. moderate and severe. Pain detection and tolerance thresholds for pressure and electric stimuli were measured in six selected dermatomes (C5, T4, T10, L1, L4 and T10BACK). In addition, the conditioned pain modulation response to cold pressor task was determined. These measures were compared between the healthy controls and chronic pancreatitis patients. Severe pancreatitis patients showed lower pain thresholds than moderate pancreatitis patients or healthy volunteers. Healthy controls showed a significantly larger conditioned pain modulation response compared to all chronic pancreatitis patients taken together.

Conclusions/Significance

The present study confirms that chronic pancreatitis patients show signs of altered central processing of nociception compared to healthy controls. The study further suggests that these changes, i.e. central sensitization, may be influenced by disease stage. These findings underline the need to take altered central pain processing into account when managing the pain of chronic pancreatitis.

The Spanish Pancreatic Club's recommendations for the diagnosis and treatment of chronic pancreatitis: part 2 (treatment)

Chronic pancreatitis (CP) is a complex disease with a wide range of clinical manifestations. This range comprises from asymptomatic patients to patients with disabling symptoms or complications. The management of CP is frequently different between geographic areas and even medical centers. This is due to the paucity of high quality studies and clinical practice guidelines regarding its diagnosis and treatment. The aim of the Spanish Pancreatic Club was to give current evidence-based recommendations for the management of CP. Two coordinators chose a multidisciplinary panel of 24 experts on this disease. These experts were selected according to clinical and research experience in CP. A list of questions was made and two experts reviewed each question. A draft was later produced and discussed with the entire panel of experts in a face-to-face meeting. The level of evidence was based on the ratings given by the Oxford Centre for Evidence-Based Medicine. In the second part of the consensus, recommendations were given regarding the management of pain, pseudocysts, duodenal and biliary stenosis, pancreatic fistula and ascites, left portal hypertension, diabetes mellitus, exocrine pancreatic insufficiency, and nutritional support in CP.

Chronic pancreatitis

PURPOSE OF REVIEW

We review important new clinical observations in chronic pancreatitis reported in 2011.

RECENT FINDINGS

Smoking increases the risk of nongallstone acute pancreatitis and the progression of acute pancreatitis to chronic pancreatitis. Binge drinking during Oktoberfest did not associate with increased hospital admissions for acute pancreatitis. The unfolded protein response is an adaptive mechanism to maintain pancreatic health in response to noxious stimuli such as alcohol. Onset of diabetes mellitus in chronic pancreatitis is likely due to progressive disease rather than individual variables. Insufficient pancreatic enzyme dosing is common for treatment of pancreatic steatorrhea; 90 000 United States Pharmacopeia units of lipase should be given with meals. Surgical drainage provides sustained, superior pain relief compared with endoscopic treatment in patients advanced chronic pancreatitis with a dilated main duct ± pancreatic stones. The central acting gabapentoid pregabalin affords a modest 12% pain reduction in patients with chronic pancreatitis but approximately 30% of patients have significant side effects.

SUMMARY

Patients with nongallstone-related acute pancreatitis or chronic pancreatitis of any cause should cease smoking. Results of this year's investigations further elucidated the pancreatic pathobiology due to alcohol, onset of diabetes mellitus in chronic pancreatitis, and the mechanisms and treatment of neuropathic pain in chronic pancreatitis.

Pain management in patients with inflammatory bowel disease: insights for the clinician

Abdominal pain is a common symptom in patients with inflammatory bowel disease (IBD) and has a profound negative impact on patients' lives. There are growing data suggesting that pain is variably related to the degree of active inflammation. Given the multifactorial etiologies underlying the pain, the treatment of abdominal pain in the IBD population is best accomplished by individualized plans. This review covers four clinically relevant categories of abdominal pain in patients with IBD, namely, inflammation, surgical complications, bacterial overgrowth, and neurobiological processes and how pain management can be addressed in each of these cases. The role of genetic factors, psychological factors, and psychosocial stress in pain perception and treatment will also be addressed. Lastly, psychosocial, pharmacological, and procedural pain management techniques will be discussed. An extensive review of the existing literature reveals a paucity of data regarding pain management specific to IBD. In addition, there is growing consensus suggesting a spectrum between IBD and irritable bowel syndrome (IBS) symptoms. Thus, this review for adult and pediatric clinicians also incorporates the literature for the treatment of functional abdominal pain and the clinical consensus from IBD and IBS experts on pharmacological, behavioral, and procedural methods to treat abdominal pain in this population.

Has central sensitization become independent of nociceptive input in chronic pancreatitis patients who fail thoracoscopic splanchnicectomy?

BACKGROUND AND OBJECTIVES

Central sensitization due to visceral pancreatic nociceptive input may be important in chronic pancreatitis pain. We investigated whether bilateral thoracoscopic splanchnicectomy (BTS) to reduce nociceptive input in chronic pancreatitis patients (CPP) with poor pain control affects supraspinal and spinal sensitization.

METHODS

Seventeen CPP were studied preoperatively and 6 weeks after BTS. Pressure pain thresholds (PPT) were measured in clavicle and pancreatic dermatomes reflecting supraspinal and spinal central sensitization, respectively. Patients with increased PPT after BTS (hypoalgesic) were compared to those without (hyperalgesic) and PPT vs. pain numeric rating scale (NRS) changes compared.

RESULTS

After BTS, ten patients showed C5 PPT increases (hypoalgesic; median change 87 kPa), 7 patients had unaltered/lower PPT (hyperalgesic; -135 kPa). Preoperative pain NRS was similar between groups (4 vs. 5, P = 0.2). After BTS hypoalgesic group NRS was lower (1 vs. 6; P = 0.008) and NRS change greater (-2 vs. 0; P = 0.005). Whole group NRS and C5 PPT change correlated significantly and negatively (r = 0.53; P < 0.05), but not for pancreatic PPT.

CONCLUSIONS

Reduced supraspinal-but not spinal-central sensitization after BTS was associated with significantly reduced pain scores in a majority of CPP. A subgroup showed no reductions in supraspinal central sensitization after BTS, coupled to no significant pain NRS reduction. Our results suggest that a subgroup of CPP has altered pain processing that may be independent of ongoing peripheral nociceptive input, resulting in persisting pain despite BTS. If confirmed, these results indicate the importance of sensory testing for indications and management of pain treatments.

Pregabalin attenuates docetaxel-induced neuropathy in rats

Chemotherapy-induced neuropathy is a serious clinical problem for patients receiving cancer treatment. The aim of this study was to investigate the potential efficacy of pregabalin in chemotherapy-induced neuropathy in rats. A total of 35 male Sprague-Dawley rats were randomly divided into 5 groups: group 1, naive control; group 2, treated with pregabalin (30 mg/kg p.o., for 8 days); group 3, docetaxel was given by single intravenous infusion at 10 mg/kg; groups 4 and 5, pregabalin at 10 mg/kg and 30 mg/kg respectively was orally administered for 8 days after the docetaxel treatment. On day 8, behavioral test was performed, and substance P and CGRP release in dorsal root ganglion (DRG) and sciatic nerve were analyzed by electron microscope. Our results showed that docetaxel induced mechanical allodynia, mechanical hyperalgesia, heat hypoalgesia, cold allodynia, and sciatic nerve impairment and substance P and CGRP release in DRG. However, oral administration of pregabalin (10 mg/kg and 30 mg/kg) for 8 consecutive days significantly attenuated docetaxel-induced neuropathy by ameliorating heat hypoalgesia, cold allodynia, impairment of sciatic nerve and reducing the release of substance P and CGRP. The findings in the present study reveal that pregabalin may be a potential treatment agent against chemotherapy-induced neuropathy.

Effects of pregabalin on central sensitization in patients with chronic pancreatitis in a randomized, controlled trial

Background

Intense abdominal pain is the dominant feature of chronic pancreatitis. During the disease changes in central pain processing, e.g. central sensitization manifest as spreading hyperalgesia, can result from ongoing nociceptive input. The aim of the present study is to evaluate the effect of pregabalin on pain processing in chronic pancreatitis as assessed by quantitative sensory testing (QST).

Methods

This randomized, double-blind, placebo-controlled trial evaluated effects of pregabalin on pain processing. QST was used to quantify pain processing by measuring thresholds to painful electrical and pressure stimulation in six body dermatomes. Descending endogenous pain modulation was quantified using the conditioned pain modulation (CPM) paradigm to elicit a DNIC (diffuse noxious inhibitory controls) response. The main effect parameter was the change in the sum of all body pain threshold values after three weeks of study treatment versus baseline values between both treatment groups.

Results

64 patients were analyzed. No differences in change in sum of pain thresholds were present for pregabalin vs. placebo after three weeks of treatment. For individual dermatomes, change vs. baseline pain thresholds was significantly greater in pregabalin vs. placebo patients for electric pain detection threshold in C5 (P = 0.005), electric pain tolerance threshold in C5 (P = 0.04) and L1 (P = 0.05), and pressure pain tolerance threshold in T4 (P = 0.004). No differences were observed between pregabalin and placebo regarding conditioned pain modulation.

Conclusion

Our study provides first evidence that pregabalin has moderate inhibitory effects on central sensitization manifest as spreading hyperalgesia in chronic pancreatitis patients. These findings suggest that QST can be of clinical use for monitoring pain treatments in the context of chronic pain.

Trial Registration

ClinicalTrials.gov NCT00755573

The absorption profile of pregabalin in chronic pancreatitis

It was recently shown that pregabalin decreased pain associated with chronic pancreatitis. It is well known that pancreatitis patients suffer from fat malabsorption with accompanying diarrhoea because of loss of exocrine pancreatic enzyme production. This may lead to changes in the mucosal surface in the small intestine and possibly affect the absorption of pregabalin. The pharmacokinetics of pregabalin has never been investigated in patients suffering from chronic pancreatitis. The aim of this study was to develop a population pharmacokinetic model of pregabalin administered to patients with chronic pancreatitis. The pregabalin population pharmacokinetic analysis was conducted on data from fifteen patients with chronic pancreatitis. Each patient received 75 mg of pregabalin (oral capsule). Pregabalin concentrations were measured using a validated liquid chromatographic method. Data analysis was performed using non-linear mixed effects modelling methodology as implemented by NONMEM. A one-compartment model with first-order absorption and elimination adequately described pregabalin pharmacokinetics. Time to maximum observed plasma concentration (T(max) ) was 1.53 (95% CI 1.09-2.05). The maximum plasma concentration (C(max) ) was 1.98 μg/ml (95% CI 1.69-2.34), and area under the plasma concentration-time profile (area under the curve) was 18.2 μg*hr/ml (95% CI 14.7-26.3). Pregabalin is well absorbed in patients with chronic pancreatitis, and the pharmacokinetic profile of pregabalin is not extensively affected by chronic pancreatitis.

Human experimental pain models for assessing the therapeutic efficacy of analgesic drugs

Pain models in animals have shown low predictivity for analgesic efficacy in humans, and clinical studies are often very confounded, blurring the evaluation. Human experimental pain models may therefore help to evaluate mechanisms and effect of analgesics and bridge findings from basic studies to the clinic. The present review outlines the concept and limitations of human experimental pain models and addresses analgesic efficacy in healthy volunteers and patients. Experimental models to evoke pain and hyperalgesia are available for most tissues. In healthy volunteers, the effect of acetaminophen is difficult to detect unless neurophysiological methods are used, whereas the effect of nonsteroidal anti-inflammatory drugs could be detected in most models. Anticonvulsants and antidepressants are sensitive in several models, particularly in models inducing hyperalgesia. For opioids, tonic pain with high intensity is attenuated more than short-lasting pain and nonpainful sensations. Fewer studies were performed in patients. In general, the sensitivity to analgesics is better in patients than in healthy volunteers, but the lower number of studies may bias the results. Experimental models have variable reliability, and validity shall be interpreted with caution. Models including deep, tonic pain and hyperalgesia are better to predict the effects of analgesics. Assessment with neurophysiologic methods and imaging is valuable as a supplement to psychophysical methods and can increase sensitivity. The models need to be designed with careful consideration of pharmacological mechanisms and pharmacokinetics of analgesics. Knowledge obtained from this review can help design experimental pain studies for new compounds entering phase I and II clinical trials.

The analgesic effect of pregabalin in patients with chronic pain is reflected by changes in pharmaco-EEG spectral indices

AIM

To identify electroencephalographic (EEG) biomarkers for the analgesic effect of pregabalin in patients with chronic visceral pain.

METHODS

This was a double-blind, placebo-controlled study in 31 patients suffering from visceral pain due to chronic pancreatitis. Patients received increasing doses of pregabalin (75mg-300mg twice a day) or matching placebo during 3 weeks of treatment. Pain scores were documented in a diary based on a visual analogue scale. In addition, brief pain inventory-short form (BPI) and quality of life questionnaires were collected prior to and after the study period. Multi-channel resting EEG was recorded before treatment onset and at the end of the study. Changes in EEG spectral indices were extracted, and individual changes were classified by a support vector machine (SVM) to discriminate the pregabalin and placebo responses. Changes in individual spectral indices and pain scores were correlated.

RESULTS

Pregabalin increased normalized intensity in low spectral indices, most prominent in the theta band (3.5-7.5Hz), difference of -3.18, 95% CI -3.57, -2.80; P= 0.03. No changes in spectral indices were seen for placebo. The maximum difference between pregabalin and placebo treated patients was seen in the parietal region, with a classification accuracy of 85.7% (P= 0.009). Individual changes in EEG indices were correlated with changes in pain diary (P= 0.04) and BPI pain composite scores (P= 0.02).

CONCLUSIONS

Changes in spectral indices caused by slowing of brain oscillations were identified as a biomarker for the central analgesic effect of pregabalin. The developed methodology may provide perspectives to assess individual responses to treatment in personalized medicine.

Cerebral excitability is abnormal in patients with painful chronic pancreatitis

BACKGROUND

We investigated whether patients with painful chronic pancreatitis (CP) present abnormalities in the cerebral response to experimental pain stimuli.

METHODS

Contact heat-evoked potentials (CHEPS) were recorded in 15 patients with CP and in 15 healthy volunteers during repetitive stimulation of the upper abdominal region (pancreatic 'viscerotome') and the right forearm (heterologous area). Three sequences of painful stimuli were applied at each site. Subjective pain scores were assessed by a visual analogue scale. Habituation was calculated as the relative change in CHEPS amplitudes between the first and the third stimulation sequence.

RESULTS

As expected pain scores decreased in healthy volunteers during successive stimulations at both sites (i.e., habituation), while in the CP group, they remained unchanged. The cerebral response consisted of an early-latency, low-amplitude response (N1, contralateral temporal region) followed by a late, high-amplitude, negative-positive complex (N2/P2, vertex). During successive stimulation of the pancreatic area, N2/P2 amplitude increased 25% in CP patients, while they decreased 20% in healthy volunteers (p = 0.006). After stimulation of the forearm, N2/P2 amplitudes increased 3% in CP patients compared to a decrease of 20% in healthy volunteers (p = 0.06).

CONCLUSIONS

Taken together, CP patients had an abnormal cerebral response to repetitive thermal stimuli. This was most prominent after stimulation of the upper abdominal area. As this area share spinal innervation with the pancreatic gland, these findings likely mirror distinctive abnormalities in cerebral pain processing.

Modern treatment of patients with chronic pancreatitis

CP remains a challenging disease. Endoscopic and surgical management, along with antioxidants, have helped in reducing chronic pain. Management of exocrine and endocrine insufficiency forms the cornerstone for improving nutrition in these patients. Newer therapeutic targets that will transcend the management of CP beyond just pain control and enzyme supplementation are required in the future.

Pancreatic nociception--revisiting the physiology and pathophysiology

BACKGROUND

Pain management of many pancreatic diseases remains a major clinical concern. This problem reflects our poor understanding of pain signaling from the pancreas.

OBJECTIVES

This review provides an overview of our current knowledge, with emphasis on current pain management strategies and recent experimental findings.

METHODS

A systematic search of the scientific literature was carried out using EMBASE, PubMed/MEDLINE, and the Cochrane Central Register of Controlled Trials for the years 1965-2011 to obtain access to all publications, especially randomized controlled trials, systematic reviews, and meta-analyses exploring pain and its management in disease states such as acute pancreatitis (AP), chronic pancreatitis (CP) and pancreatic cancer (PC).

RESULTS

Over the last decade, numerous molecular mediators such as nerve growth factor and the transient receptor potential (TRP) cation channel family have been implicated in afferent nerve signaling. More recent animal studies have indicated the location of the receptive fields for the afferent nerves in the pancreas and shown that these are activated by agents including cholecystokinin octapeptide, 5-hydroxytryptamine and bradykinin. Studies with PC specimens have shown that neuro-immune interactions occur and numerous agents including TRP cation channel V1, artemin and fractalkine have been implicated. Experimental studies in the clinical setting have demonstrated impairment of inhibitory pain modulation from supraspinal structures and implicated neuropathic pain mechanisms.

CONCLUSIONS

Our knowledge in this area remains incomplete. Characterization of the mediators and receptors/ion channels on the sensory nerve terminals are required in order to facilitate the development of new pharmaceutical treatments for AP and CP.

Unraveling the mystery of pain in chronic pancreatitis

Chronic pancreatitis is typically a painful condition and it can be associated with a severe burden of disease. The pathogenesis of pain in this disorder is poorly understood and its treatment has been largely empirical, often consisting of surgical or other invasive methods, with an outcome that is variable and frequently unsatisfactory. Human and experimental studies have indicated a critical role for neuronal mechanisms that result in peripheral and central sensitization. The pancreatic nociceptor seems to be significantly affected in this condition, with increased excitability associated with downregulation of potassium currents. Some of the specific molecules implicated in this process include the vanilloid receptor, TRPV1, nerve growth factor, the protease activated receptor 2 and a variety of others that are discussed in this Review. Studies have also indicated novel therapeutic targets for this condition.

Randomised clinical trial: pregabalin attenuates experimental visceral pain through sub-cortical mechanisms in patients with painful chronic pancreatitis

BACKGROUND

Pregabalin has a broad spectrum of analgesic and antihyperalgesic activity in both basic and clinical studies. However, its mechanisms and sites of action have yet to be determined in humans.

AIMS

To assess the antinociceptive effect of pregabalin on experimental gut pain in patients with visceral hyperalgesia due to chronic pancreatitis and to reveal putative changes in corresponding central pain processing as assessed by evoked brain potentials.

METHODS

Thirty-one patients were randomly assigned to receive increasing doses of pregabalin or placebo for three consecutive weeks. Perceptual thresholds to electrical stimulation of the sigmoid with recording of corresponding evoked brain potentials were obtained at baseline and study end. The brain source localisations reflecting direct neuronal activity were fitted by a five-dipole model projected to magnetic resonance imaging of the individuals' brains.

RESULTS

As compared to placebo, pregabalin significantly increased the pain threshold to electrical gut stimulation from baseline (P=0.02). No differences in evoked brain potential characteristics were seen, neither after pregabalin nor placebo treatment (all P>0.05). In agreement with this, brain source locations remained stable during study treatment (all P>0.05).

CONCLUSION

Pregabalin was superior to placebo for attenuation of experimental visceral pain in chronic pancreatitis patients. We suggest its antinociceptive effects to be mediated primarily through sub-cortical mechanisms.