Hans G. Kress

Clinical update on the pharmacology, efficacy and safety of transdermal buprenorphine

Buprenorphine was not used widely in clinical practice over many years, mainly due to analgesic potency and clinical safety concerns based on misinterpreted animal data. Contrary to previous concerns, however, no analgesic ceiling effect and no antagonism of combined pure μ‐opioid receptor agonists is seen within the therapeutic dose range. In recent studies, buprenorphine could be effectively and safely combined with full μ‐agonists, and switching between buprenorphine and another opioid provided comparable pain relief based on equianalgesic doses. Moreover, buprenorphine exerts an antihyperalgesic effect, which is due—at least in part—to antagonistic activity at κ‐opioid receptors.

Efficacy and tolerability of intranasal fentanyl spray 50 to 200 μg for breakthrough pain in patients with cancer: A phase III, multinational, randomized, double-blind, placebo-controlled, crossover trial with a 10-month, open-label extension treatment period

OBJECTIVE This trial investigated the efficacy and long-term tolerability of intranasal fentanyl spray (INFS) 50 to 200 microg in the treatment of breakthrough pain in opioid-tolerant patients with cancer. METHODS This Phase III, double-blind, randomized, placebo-controlled, crossover trial was conducted at pain centers, anesthesiology departments, palliative care units, and oncology clinics in Austria, Denmark, France, Germany, and Poland. Eligible patients were adults with cancer receiving a stable dose of long-term opioid treatment for the control of background pain. Patients were treated at home with their effective dose of INFS (50, 100, or 200 microg) or inactive spray (placebo) in a randomized sequence for 3 weeks, followed by a 10-month, open-label tolerability phase during which they received their effective dose of INFS. Throughout the study, patients were allowed to use their usual rescue medication, which was recorded in patient diaries. The primary efficacy end point was the pain intensity difference at 10 minutes after study drug administration (PID(10)), as assessed using an 11-point numeric rating scale (0 = no pain to 10 = worst pain imaginable). An effect size of 0.5 for PID was considered clinically relevant. The rate of response, defined as PID(10) >2, was also assessed. Adverse events (AEs) were recorded in patient diaries during the efficacy period and reported in monthly clinic visits and follow-up weekly telephone contacts during the extension period. RESULTS In all, 120 patients were enrolled and achieved an effective dose; 113 were randomized and 111 were included in the intent-to-treat analysis set (56 men, 55 women; mean [SD] age, 60.6 [9.45] years; mean weight, 70.3 kg [men] and 65.3 kg [women]; white race, 107 [96.4%]; INFS 50 microg, 18; INFS 100 microg, 48; INFS 200 microg, 45; placebo, 110). PID(10) with INFS was 2-fold that with placebo (adjusted means, 2.36 vs 1.10; adjusted difference, 1.26 [greater than the clinically relevant difference of 0.5]; P < 0.001). Additional analysis revealed that the mean response rate with all 3 doses of INFS was 51.1% versus 20.9% with placebo. The prevalence of AEs was 22/111 (19.8%) during the efficacy period, during which the most frequently reported AEs were nausea (5 [4.5%]) and vertigo (2 [1.8%]). No serious AEs were considered related to the study drugs. In all, 108 patients entered the extension period, with a mean duration of exposure to INFS of 134.9 days. Progression of underlying malignant disease was the most common AE reported during this period (55 [50.9%]); this event was not considered treatment related. CONCLUSIONS In these opioid-tolerant patients with cancer, INFS at doses of 50, 100, and 200 microg was associated with an onset of activity at 10 minutes and effective treatment of breakthrough pain compared with placebo. All doses were generally well tolerated and clinically efficacious.

The Short- and Long-Term Benefit in Chronic Low Back Pain Through Adjuvant Electrical Versus Manual Auricular Acupuncture

Acupuncture is an established adjuvant analgesic modality for the treatment of chronic pain. Electrical stimulation of acupuncture points is considered to increase acupuncture analgesia. In this prospective, randomized, double-blind, controlled study we tested the hypothesis that auricular electroacupuncture (EA) relieves pain more effectively than conventional manual auricular acupuncture (CO) in chronic low back pain patients with insufficient pain relief (visual analogue scale [VAS] ≥5) treated with standardized analgesic therapy. Disposable acupuncture needles were inserted in the auricular acupuncture points 29, 40, and 55 of the dominant side and connected to a newly developed battery-powered miniaturized stimulator worn behind the ear. Patients were randomized into group EA (n = 31) with continuous low-frequency auricular EA (1 Hz biphasic constant current of 2 mA) and group CO (n = 30) without electrical stimulation (sham-electroacupuncture). Treatment was performed once weekly for 6 wk, and in each group needles were withdrawn 48 h after insertion. During the study period and a 3-mo follow-up, patients were asked to complete the McGill questionnaire. Psychological well being, activity level, quality of sleep, and pain intensity were assessed by means of VAS; moreover, analgesic drug consumption was documented. Pain relief was significantly better in group EA during the study and the follow-up period as compared with group CO. Similarly, psychological well-being, activity, and sleep were significantly improved in group EA versus group CO, the consumption of analgesic rescue medication was less, and more patients returned to full-time employment. Neuropathic pain in particular improved in patients treated with EA. There were no adverse side effects. These results are the first to demonstrate that continuous EA stimulation of auricular acupuncture points improves the treatment of chronic low back pain in an outpatient population.

Tapentadol and its two mechanisms of action: Is there a new pharmacological class of centrally-acting analgesics on the horizon?

Tapentadol is a novel centrally-acting analgesic, that exerts its analgesic effects through l-opioid receptor (MOR) agonism and noradrenaline reuptake inhibition (NRI). In this issue of EJP, Schröder et al. describe the differential contribution of lopioid and noradrenergic mechanisms to the antinociceptive and antihyperalgesic efficacy of tapentadol in rat models of nociceptive and neuropathic pain. In June 2009, an international group of experts in neuropharmacology and pain research met to discuss the roles of these two important mechanisms in the processing of pain, and the importance of their pharmacological modulation for analgesia. During the discussion of the pharmacological profile of tapentadol it became obvious that apparently there are differences between tapentadol and other centrallyacting drugs and the suggestion was made to consider tapentadol a representative of a new pharmacological class of drugs, the MOR-NRI (l-opioid receptor agonist noradrenaline reuptake inhibitor).

The Absence of Acute Tolerance During Remifentanil Infusion in Volunteers

The development of acute opioid tolerance in humans remains controversial. We tested the hypothesis that continuous remifentanil infusion leads to rapid development of opioid tolerance. Twenty healthy male volunteers were enrolled onto a randomized, placebo-controlled, double-blinded, cross-over design study to receive a 3 h continuous infusion of remifentanil (0.08 &mgr;g · kg−1 · min−1) or saline. Test procedures included determination of pain perception thresholds and pain tolerance thresholds to heat and cold and neuroselective sine wave constant current at 5 Hz and 250 Hz. Test procedures were performed at baseline and then repeated at 25, 55, 85, 115, and 160 min (heat/cold) and at 35, 65, 95, 125, and 170 min (electrical current) during infusion. No significant decrease of the pain threshold devolutions between 55 and 180 min after the start of infusion of remifentanil could be detected. In conclusion, no development of acute opioid tolerance was observed during constant remifentanil infusion of 3 h in volunteers.

Lack of analgesia by oral standardized cannabis extract on acute inflammatory pain and hyperalgesia in volunteers.

Background:Cannabinoid-induced analgesia was shown in animal studies of acute inflammatory and neuropathic pain. In humans, controlled clinical trials with &Dgr;9-tetrahydrocannabinol or other cannabinoids demonstrated analgesic efficacy in chronic pain syndromes, whereas the data in acute pain were less conclusive. Therefore, the aim of this study was to investigate the effects of oral cannabis extract in two different human models of acute inflammatory pain and hyperalgesia. Methods:The authors conducted a double-blind, crossover study in 18 healthy female volunteers. Capsules containing &Dgr;9-tetrahydrocannabinol–standardized cannabis extract or active placebo were orally administered. A circular sunburn spot was induced at one upper leg. Heat and electrical pain thresholds were determined at the erythema, the area of secondary hyperalgesia, and the contralateral leg. Intradermal capsaicin-evoked pain and areas of flare and secondary hyperalgesia were measured. Primary outcome parameters were heat pain thresholds in the sunburn erythema and the capsaicin-evoked area of secondary hyperalgesia. Secondary measures were electrical pain thresholds, sunburn-induced secondary hyperalgesia, and capsaicin-induced pain. Results:Cannabis extract did not affect heat pain thresholds in the sunburn model. Electrical thresholds (250 Hz) were significantly lower compared with baseline and placebo. In the capsaicin model, the area of secondary hyperalgesia, flare, and spontaneous pain were not altered. Conclusion:To conclude, no analgesic or antihyperalgesic activity of cannabis extract was found in the experiments. Moreover, the results even point to the development of a hyperalgesic state under cannabinoids. Together with previous data, the current results suggest that cannabinoids are not effective analgesics for the treatment of acute nociceptive pain in humans.

The sunburn pain model: the stability of primary and secondary hyperalgesia over 10 hours in a crossover setting.

It was our aim to study the within-day stability and between-day repeatability of ultraviolet B (UVB) light-induced primary and secondary hyperalgesia over 10 h. Twenty hours after UVB irradiation of a skin spot (r = 2.5 cm) on the upper leg of 8 healthy volunteers the areas of secondary hyperalgesia to pinprick and pain tolerance thresholds to heat (HPTT) and electrical stimuli (5 and 250 Hz, electrical pain tolerance thresholds [EPTT]) were assessed. Measurements were repeated for 10 h at 2-h intervals and in 2 different sessions. Large areas of secondary hyperalgesia to pin prick were observed (5995 mm2; sd, 1645). Primary hyperalgesia was evidenced by significant decreases of HPTT (mean difference, 6.5°C; 95% confidence interval, 6.1–6.8; P < 0.001) and EPTT at 250 Hz (mean difference, 0.45 mA; 95% confidence interval, 0.13–0.78; P < 0.05) compared to normal skin. There was no trend within one session of either primary (P = 0.14 for HPTT) or secondary hyperalgesia (P = 0.95) and no difference between the two sessions (primary hyperalgesia, P = 0.28; secondary hyperalgesia, P = 0.07). The sunburn pain model provides a long time course of stable hyperalgesia with a high within-day stability and between-day repeatability for primary and secondary hyperalgesia

Effectiveness and safety of tapentadol prolonged release for severe, chronic low back pain with or without a neuropathic pain component: results of an open-label, phase 3b study

Abstract Objective: This open-label, phase 3b study evaluated the effectiveness and tolerability of tapentadol prolonged release and tapentadol immediate release (for acute pain episodes) for severe, chronic low back pain with or without a neuropathic pain component that was inadequately managed in patients taking World Health Organization (WHO) Step I or II analgesics or who were not regularly treated with analgesics. Research design and methods: Average baseline pain intensity was greater than 5 (11-point numerical rating scale-3 [NRS-3; 3-day average pain intensity]) with WHO Step I or II analgesics and greater than 6 with no regular analgesic regimen. WHO Step II analgesics were discontinued before starting study treatment; WHO Step I analgesics or co-analgesics were continued at the same dose. Patients received tapentadol prolonged release (50–250 mg bid) during a 5-week titration and 7-week maintenance period. Tapentadol immediate release was permitted for acute pain episodes (tapentadol prolonged release and immediate release maximum combined dose, ≤500 mg/day). The painDETECT questionnaire was used to define subsets of patients based on the probability of a neuropathic pain component to their low back pain as ‘negative’, ‘unclear’, or ‘positive’. Clinical trial registration: NCT00983385. Main outcome measure: The primary endpoint was the change from baseline to week 6 in average pain intensity (NRS-3), using the last observation carried forward to impute missing scores. Results: In the painDETECT negative (n = 49) and unclear/positive (n = 126) subsets, respectively, mean (SD) changes in pain intensity from baseline to week 6 were −2.4 (2.18) and −3.0 (2.07; both p < 0.0001). Among patients who had not received prior WHO Step II treatment, lower doses of tapentadol prolonged release were generally required with increasing likelihood of a neuropathic pain component. Based on the painDETECT questionnaire and the Neuropathic Pain Symptom Inventory (NPSI), tapentadol prolonged release treatment was also associated with significant improvements in neuropathic pain symptoms, with decreases in the number of pain attacks and the duration of spontaneous pain in the last 24 hours in patients with low back pain with a neuropathic pain component (painDETECT unclear or positive score at baseline or screening). The most common treatment-emergent adverse events (incidence ≥10%, n = 176) were nausea, dizziness, headache, dry mouth, fatigue, constipation, diarrhea, nasopharyngitis, and somnolence. Conclusions: Tapentadol prolonged release was well tolerated and effective for managing severe, chronic low back pain with or without a neuropathic pain component.

Opioid medication and driving ability.

In many European countries the use of opioids for long‐term treatment of nonmalignant pain has dramatically increased during the last decade in order to improve the patients quality of life, to allow an active social life and the return to work. In modern society, driving is regarded as an essential activity of daily living. Since opioids are centrally acting drugs that may interfere with the ability of safely driving a motor vehicle, the question arises of whether or not and on which conditions patients under continuous opioid medication may be considered fit to drive. In this article the evidence from recent studies of opioid effects on driving ability of patients is reviewed. Based on these data, the prerequisites and restrictions for driving under chronic opioid medication are outlined and practical guidelines are proposed.

The procoagulatory effects of delta-9-tetrahydrocannabinol in human platelets.

Delta-9-tetrahydrocannabinol (THC) is increasingly used for the long-term treatment of nausea, vomiting, cachexia, and chronic pain. Recent reports, however, have indicated an increased risk of myocardial infarction and thromboangiitis obliterans after THC intake. Blood platelets have an essential role in the pathogenesis of these two diseases, but it is unclear whether platelets are potential target cells for cannabinoids. We investigated the effects of THC on human platelets and the expression of cannabinoid receptors on their cell membranes in this in vitro study. The effects of THC (final concentrations 10−7 to 10−5 M) on the expression of activated platelet fibrinogen receptor (glycoprotein IIb-IIIa) and P selectin were characterized by flow cytometry. Western blotting was performed with platelet membrane preparations to determine the surface expression of cannabinoid receptors on human platelets. THC increased the expression of glycoprotein IIb-IIIa and P selectin on human platelets in a concentration-dependent manner. The two known cannabinoid receptors (CB1 and CB2) were both detected on the cell membrane of human platelets. Our functional results may suggest a receptor-dependent pathway of THC-induced platelet activation. However, further in vivo studies are warranted to evaluate the role of cannabinoid receptors in mediating the demonstrated procoagulatory effect of THC.