Disambiguating pharmacological mechanisms from placebo in neuropathic pain using functional neuroimaging.

BACKGROUND: A lack of objective outcome measures and overreliance on subjective pain reports in early proof-of-concept studies contribute to the high attrition of potentially effective new analgesics. We studied the utility of neuroimaging in providing objective evidence of neural activity related to drug modulation or a placebo effect in a double-blind, randomized, placebo-controlled, three-way crossover trial. METHODS: We chronically administered pregabalin or tramadol (first-line and second-line analgesics, respectively), recommended for neuropathic pain, in 16 post-traumatic neuropathic pain patients. We measured subjective pain reports, allodynia-evoked neural activity, and brain resting state functional connectivity from patients during the three sessions and resting state data at baseline from patients after washout of their current medication. All data were collected using a 3 T MRI scanner. RESULTS: When compared with placebo only, pregabalin significantly suppressed allodynia-evoked neural activity in several nociceptive and pain-processing areas of the brain, despite the absence of behavioural analgesia. Furthermore, placebo significantly increased functional connectivity between the rostral anterior cingulate and the brainstem, a core component of the placebo neural network. CONCLUSIONS: Functional neuroimaging provided objective evidence of pharmacodynamic efficacy in a proof-of-concept study setting where subjective pain outcome measures are often unreliable. Additionally, we provide evidence confirming the neural mechanism underpinning placebo analgesia as identified in acute experimental imaging studies in patients during the placebo arm of a clinical trial. We explore how brain penetrant active drugs potentially interact with this mechanism. CLINICAL TRIAL REGISTRATION: NCT0061015.

Can skin disease cause neuropathic pain? A study in pachyonychia congenita.

INTRODUCTION: Pachyonychia congenita (PC) is a rare skin disorder caused by an autosomal dominant mutation in one of five genes encoding keratin (K6a, K6b, K6c, K16 or K17; each defining one PC subtype). Pain is a prominent symptom, but its severity and type are poorly characterized. METHODS: In total, 35 genotyped US patients with PC consented to clinical assessment including the quality of life (QoL) questionnaire EQ-5D-3L, the Brief Pain Inventory (BPI) and painDETECT. Abbreviated quantitative sensory testing (QST) was also performed, and included mechanical detection threshold (MDT), mechanical pain threshold (MPT), wind-up pain ratio (WUR) and vibration detection threshold (VDT). RESULTS: Significant pain in patients with PC was confirmed, as indicated by mean BPI severity and interference of 4.2 ± 1.7 and 4.4 ± 2.2, respectively, as well as QoL impairment, as indicated by mean EQ-5D index of 0.69 ± 0.18. PD identified neuropathic pain in 62% of patients, the remainder being nociceptive. The painDETECT score was most significantly related to EQ-5D index (R(2)  = 0.26, P = 0.02). The K17 and K6a subtypes exhibited significantly worse QoL (0.584 and 0.613 respectively) than the K16 and K6b subtypes (P = 0.02). In QST analysis, abnormal pressure pain (assessed as MPT) was frequently observed, with more than half of patients with PC affected (54%), and 57% of patients with K17 also exhibiting abnormality in minimum touch threshold (assessed as MDT, P < 0.05). Very few patients were receiving analgesic therapy appropriate for neuropathic pain. CONCLUSION: Significant neuropathic pain was observed in PC, which warrants appropriate treatment. The health states observed in this sample are at a level that the average US citizen would forfeit one-third of their remaining lifespan to avoid.

A multicentre, open-label, follow-on study to assess the long-term maintenance of effect, tolerance and safety of THC/CBD oromucosal spray in the management of neuropathic pain.

Peripheral neuropathic pain (PNP) poses a significant clinical challenge. The long-term efficacy of delta-9-tetrahydrocannabinol (THC)/cannabidiol (CBD) oromucosal spray was investigated in this 38-week open-label extension study. In total, 380 patients with PNP associated with diabetes or allodynia entered this study from two parent randomised, controlled trials. Patients received THC/CBD spray for a further 38 weeks in addition to their current analgesic therapy. Neuropathic pain severity was the primary efficacy measure using a pain 0-10 numerical rating scale (NRS). Additional efficacy, safety and tolerability outcomes were also investigated. In total, 234 patients completed the study (62 %). The pain NRS showed a decrease in score over time in patients from a mean of 6.9 points (baseline in the parent studies) to a mean of 4.2 points (end of open-label follow-up). The proportion of patients who reported at least a clinically relevant 30 % improvement in pain continued to increase with time (up to 9 months); at least half of all patients reported a 30 % improvement at all time points. Improvements were observed for all secondary efficacy outcomes, including sleep quality 0-10 NRS scores, neuropathic pain scale scores, subject global impression of change and EQ-5D questionnaire scores. THC/CBD spray was well tolerated for the study duration and patients did not seek to increase their dose with time, with no new safety concerns arising from long-term use. In this previously difficult to manage patient population, THC/CBD spray was beneficial for the majority of patients with PNP associated with diabetes or allodynia.

What the patients say: A study of reactions to an intensive care unit.

One hundred consecutive patients were interviewed between the 3rd and 7th days, inclusive, of their discharge from an intensive care unit to a general ward. The patients' recall of events related to their admission to the ICU was generally poor, and 41% of them felt that they had been confused at some time during their stay though much of this seems to have passed unnoticed by the nursing staff. Lack of sleep was a problem to about a quarter of the patients and 75% of these thought that the inability to lie comfortably was a factor preventing sleep. Other factors included pain, anxiety and noise. The patients seemed satisfied whilst in the ICU, and less than half said they were pleased to return to a general ward.