Tapentadol treatment results in long-term pain relief in patients with chronic low back pain and associates with reduced segmental sensitization.

INTRODUCTION: Chronic low back pain (CLBP) is one of the most common chronic pain conditions in pain practice. OBJECTIVES: In the current study, we describe phenotypes of patients with CLBP based on the status of their endogenous pain modulatory system. METHODS: Conditioned pain modulation (a measure of central pain inhibition), temporal summation (TS, a measure of pain facilitation), and offset analgesia (a measure of temporal filtering of nociception) were evaluated in 53 patients with CLBP at painful and nonpainful sites. Next, in a double-blind, randomized, placebo-controlled trial, 40 patients with defective conditioned pain modulation responses received treatment with tapentadol prolonged-release or placebo for 3 months. RESULTS: The majority of patients (87%) demonstrated loss of central pain inhibition combined with segmentally increased TS and reduced offset analgesia at the lower back region. During treatment, tapentadol reduced pain intensity more than placebo (tapentadol -19.5 ± 2.1 mm versus placebo -7.1 ± 1.8 mm, P = 0.025). Furthermore, tapentadol significantly decreased pain facilitation by reduction of TS responses at the lower back (tapentadol -0.94 ± 1.9 versus placebo 0.01 ± 1.5, P = 0.020), which correlated with pain reduction (P < 0.001). CONCLUSION: Patients with CLBP demonstrated different phenotypes of endogenous pain modulation. In patients with reduced conditioned pain modulation, tapentadol produced long-term pain relief that coincided with reduction of signs of pain facilitation. These data indicate that the endogenous pain system may be used as a biomarker in the pharmacological treatment of CLBP, enabling an individualized, mechanism-based treatment approach.

Cornea nerve fibre state determines analgesic response to tapentadol in fibromyalgia patients without effective endogenous pain modulation.

BACKGROUND: Tapentadol is a centrally acting analgesic with µ-agonistic activity combined with noradrenaline reuptake inhibition. Its mechanism of action relies on improvement of descending pain inhibition. In the current study, tapentadol's ability to enhance conditioned pain modulation (CPM, an experimental measure of descending pain inhibition) was evaluated in fibromyalgia patients with absent or reduced CPM responses. METHODS: A total of 34 fibromyalgia patients completed this double-blind trial. Patients were randomized to receive treatment with tapentadol sustained-release or placebo for a 3-month period with 1-month follow-up. At baseline, the cornea nerve fibre state (CNFS) was quantified to determine the presence of nerve fibre pathology and assess its value in the prediction of the analgesic response. RESULTS: Tapentadol significantly increased CPM responses during treatment with an average increase from baseline of 20.5 ± 12.5% (tapentadol) versus 3.0 ± 11.2% (placebo; p = 0.042). No treatment effect was observed for the absolute pain scores, however, analgesia responder rate analyses demonstrated a treatment effect in favour of tapentadol. Pain relief (a reduction in pain score ≥ 30%) was predicted by the presence of a normal CNFS (p = 0.035). Patients with an abnormal CNFS had no analgesic effect from tapentadol despite an increase in CPM. CONCLUSIONS: In chronic pain patients with fibromyalgia, the increase in endogenous pain inhibition by tapentadol was translated into analgesia in patients with a normal CNFS. In those with abnormal CNFS, tapentadol treatment was without analgesic effect. SIGNIFICANCE: In this double-blind randomized placebo-controlled trial, we showed that tapentadol significantly enhanced the descending pain inhibition in fibromyalgia patients. Tapentadol-induced pain relief was only present in patients with a normal CNFS.

An experimental randomized study on the analgesic effects of pharmaceutical-grade cannabis in chronic pain patients with fibromyalgia.

In this experimental randomized placebo-controlled 4-way crossover trial, we explored the analgesic effects of inhaled pharmaceutical-grade cannabis in 20 chronic pain patients with fibromyalgia. We tested 4 different cannabis varieties with exact knowledge on their [INCREMENT]-tetrahydrocannabinol (THC) and cannabidiol (CBD) content: Bedrocan (22.4-mg THC, <1-mg CBD; Bedrocan International BV, Veendam, the Netherlands), Bediol (13.4-mg THC, 17.8-mg CBD; Bedrocan International BV, Veendam, the Netherlands), Bedrolite (18.4-mg CBD, <1-mg THC; Bedrocan International BV, Veendam, the Netherlands), and a placebo variety without any THC or CBD. After a single vapor inhalation, THC and CBD plasma concentrations, pressure and electrical pain thresholds, spontaneous pain scores, and drug high were measured for 3 hours. None of the treatments had an effect greater than placebo on spontaneous or electrical pain responses, although more subjects receiving Bediol displayed a 30% decrease in pain scores compared to placebo (90% vs 55% of patients, P = 0.01), with spontaneous pain scores correlating with the magnitude of drug high (ρ = -0.5, P < 0.001). Cannabis varieties containing THC caused a significant increase in pressure pain threshold relative to placebo (P < 0.01). Cannabidiol inhalation increased THC plasma concentrations but diminished THC-induced analgesic effects, indicative of synergistic pharmacokinetic but antagonistic pharmacodynamic interactions of THC and CBD. This experimental trial shows the complex behavior of inhaled cannabinoids in chronic pain patients with just small analgesic responses after a single inhalation. Further studies are needed to determine long-term treatment effects on spontaneous pain scores, THC-CBD interactions, and the role of psychotropic symptoms on pain relief.

Ketamine for cancer pain: what is the evidence?

PURPOSE OF REVIEW: In this review, we assess the benefit of ketamine in the treatment of terminal cancer pain that is refractory to opioid treatment and/or complicated by neuropathy. RECENT FINDINGS: While randomized controlled trials consistently show lack of clinical efficacy of ketamine in treating cancer pain, a large number of open-label studies and case series show benefit. SUMMARY: Ketamine is an N-methyl-D-aspartate receptor antagonist that at low-dose has effective analgesic properties. In cancer pain, ketamine is usually prescribed as adjuvant to opioid therapy when pain becomes opioid resistant or when neuropathic pain symptoms dominate the clinical picture. A literature search revealed four randomized controlled trials that examined the benefit of oral, subcutaneous or intravenous ketamine in opioid refractory cancer pain. None showed clinically relevant benefit in relieving pain or reducing opioid consumption. This suggests absence of evidence of benefit for ketamine as adjuvant analgesic in cancer pain. These findings contrast the benefit from ketamine observed in a large number of open-label studies and (retrospective) case series. We relate the opposite outcomes to methodological issues. The complete picture is such that there is still insufficient evidence to state with certainty that ketamine is not effective in cancer pain.

Ketamine for pain.

The efficacy of the N-methyl-D-aspartate receptor antagonist ketamine as an analgesic agent is still under debate, especially for indications such as chronic pain. To understand the efficacy of ketamine for relief of pain, we performed a literature search for relevant narrative and systematic reviews and meta-analyses. We retrieved 189 unique articles, of which 29 were deemed appropriate for use in this review. Ketamine treatment is most effective for relief of postoperative pain, causing reduced opioid consumption. In contrast, for most other indications (that is, acute pain in the emergency department, prevention of persistent postoperative pain, cancer pain, and chronic non-cancer pain), the efficacy of ketamine is limited. Ketamine's lack of analgesic effect was associated with an increase in side effects, including schizotypical effects.

The first cases of collagenous sprue successfully treated with thioguanine.

OBJECTIVE: Collagenous sprue (CS) is a rare form of small bowel enteropathy characterised by a thickened basement membrane and is, in most of the literature, reported as part of coeliac disease. Multiple treatment strategies are suggested in CS, but there is no standardised therapy. The aim of this series is to describe 4 cases of CS and to propose thioguanine (6-TG) treatment. DESIGN: We reviewed 4 cases of CS. Data were obtained from our prospective database of patients referred to our coeliac centre. Evaluation of small bowel biopsies was performed by an expert pathologist. RESULTS: None of the patients had ever had coeliac-specific antibodies, and all were negative for HLA-DQ2 and HLA-DQ8 phenotype. Three patients were treated with a combination of 6-TG and budesonide, and 1 patient received 6-TG only. All patients improved remarkably. Normalisation of the thickened basement membrane was found in 2 patients and complete histological improvement including full recovery of villi was found in 1 patient. In the third patient, the thickened basement membrane was only very focally recognised. The thickened membrane persisted in the last patient, probably because of the short time of follow-up. CONCLUSIONS: CS should be separated from coeliac disease. Based on the lack of typical HLA phenotyping and the absence of coeliac-specific antibodies, there seems to be no relation with coeliac disease in these 4 cases. A promising treatment option might be 6-TG with or without budesonide. Research in a larger cohort is needed to standardise treatment for CS.