Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an opioid characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action, since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol limits the risk of opioid-related adverse events, such as gastrointestinal disturbances. Moreover, the NA component becomes predominant, at least, in some types of pain, with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of severe uncontrolled chronic pain characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an analgesic molecule characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol has two important consequences: first, it limits the risk of opioid-related adverse events, as well as the risk of dependence; second, the NA component becomes predominant at least in some types of pain with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of chronic pain conditions characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Tapentadol: an analgesic that differs from classic opioids due to its noradrenergic mechanism of action

Chronic pain treatment represents one of the most complex clinical challenges and even though opioids exhibit particular efficacy on nociceptive pain, their use must be controlled to avoid the risk of adverse reactions. A useful approach, aimed at maintaining analgesia and mitigating side effects, is represented by the use of a new class of analgesics endowed of µ-opioid (MOR) receptor agonism and noradrenaline reuptake inhibition (NRI) mechanisms. Tapentadol is the progenitor of this new class of drugs called MOP-NRI. A literature review has been conducted to gain information about the efficacy and the tolerability profile of tapentadol shifting from MOR agonism (acute pain) to NRI activity (chronic pain). The tolerability and therapeutic safety of tapentadol in neuropathic pain models, as well as in clinical settings, has been analyzed showing a good gastrointestinal tolerability profile, a moderate effect on hormone levels (in healthy volunteers and in patients) and on cognitive performance, a lack of significant alteration of the electrocardiogram recording and no changes of the QT/QTc interval, a minimal effect on serotonin reuptake in vivo with a low risk of serotonin syndrome, a longer time for the onset of analgesic tolerance and a less occurrence of abuse liability compared to formulations containing other comparator compounds. Tapentadol represents a great innovation in chronic pain therapy with a unique analgesic profile different form classical opioids, therefore, thanks to its synergistic MOR-NRI action, it may be a good option for the treatment of chronic, neuropathic and mixed pain.

Oxatomide in Food Allergies. Comparative Study versus Disodium Chromoglycate

A randomized, controlled, single blind study was carried out to compare the efficacy and safety of oxatomide and disodium chromoglycate in the treatment of adverse reactions to food.

Twenty-three patients (16F and 7M) with urticaria (16 patients), respiratory (5 patients), intestinal (15 patients) and/or neurological symptoms (3 patients) were treated for 60 days: 14 (9F and 5M; mean ± SD age 36.3 ± 13.8 years) with oxatomide, 60 mg every evening and 9 (7F and 2M; 31.5 ± 15.1 years) with disodium chromoglycate, 500 mg three times a day. Both therapies lasted two months. On admission and after 15,30 and 60 days skin (wheals, itching, vesicular blisters, scratching lesions), respiratory (rhinorrhea, sneezing, coughing, wheezing), intestinal (constipation, diarrhea, bloating, abdominal pain and/or cramps) and neurological (headache, irritability) symptoms were assessed.

Wheals decreased in number and size in both groups (p<0.005). Itching became less severe in the two groups (p<0.05), although the improvement in the oxatomide group was faster. Vesicular blisters, present in one patient in the oxatomide group at baseline, disappeared by days 15 and 30, reappearing in a mild form at the end of the study. The frequency of scratching lesions decreased. Sneezing and wheezing disappeared in both groups. Digestive system symptoms also improved.

Both treatments were effective as regards cutaneous, intestinal and respiratory symptoms, with a significant reduction of itching, wheals and vesicular blisters and the complete relies of intestinal disorders. The drugs were well tolerated.

Pain in cancer. An outcome research project to evaluate the epidemiology, the quality and the effects of pain treatment in cancer patients

BACKGROUND

Management of pain related to advanced or metastatic cancer, although the availability of several pharmacological and non-pharmacological interventions and the existence of well-known guidelines and protocols, is often difficult and inadequate. Evidence of the relative effectiveness of current options for treating cancer pain from comparative randomized studies is scanty.

METHODS

In the context of a wider project, a multicenter, open label, prospective Outcome Research study will be launched in Italy in 2006 to investigate the epidemiology of cancer pain and of its treatments, the quality of analgesic-drug therapy and the effectiveness of alternative analgesic strategies in a large, prospective, unselected cohort of cancer patients using the state-of-the art of patient-reported-outcomes. About 100 Italian centers will recruit 2500 patients with advanced/progressive/metastatic cancer with pain (related to the cancer disease) requiring analgesic treatments. Each center is expected to recruit 25 consecutive and eligible patients during the study inception period. Approximately two months will be allowed for subject recruitment and enrollment. Subject evaluation and follow-up will be for 3 months. The effect on outcomes of various therapeutic analgesic options administered by physicians, given the observational approach where patients are not assigned at random to different treatments, will be compared using the propensity score approach, allowing the adjustment for treatment selection bias. Later, after the launch of the observational study and on the basis of results, in specific subsamples of patients and in select centers of the network, a Randomized Controlled Trial will be carried out to formally compare the efficacy of alternative analgesic strategies, with particular emphasis on oral morphine (as comparator) and buprenorphine patch (as experimental arm). Results from the outcome (cohort) and experimental (Randomized Controlled Trial) studies will ensure both the external and internal validity.

[Protective effect of oxatomide in infantile bronchial asthma. Double-blind study vs placebo]

BACKGROUND

This study has been designed to assess the protective effect of oxatomide in allergic bronchial asthma of the seasonal type in young children.

METHODS

The study was carried out in a paediatric clinic; sixteen children divided into two balanced groups took oxatomide in an oral suspension at the dosage of 1 mg/kg/day, or placebo for a period of 2 months. Eight patients (7 males, 1 female), aged 22 months +/- 2.83 (mean +/- SD) took oxatomide in an oral suspension at the dosage of 1 mg/kg/day, while the other eight (3 males, 5 females; 22.13 months +/- 3.48) took placebo. Efficacy was assessed by monitoring cough, dyspnea at rest, dyspnea following exercise, wheezing, sleep disorders at baseline and after 15, 30 and 60 days of treatment, on the basis of a semiquantitative scale. All side effects were recorded.

RESULTS

Persistent coughing was significantly reduced (p < 0.05) after two weeks' treatment with oxatomide. Sleep disorders and other symptoms remarkably improved. Dyspnea at rest and following exercise disappeared after 15 days' therapy, while the intensity of wheezing decreased after 30 days' active treatment. In all parameters examined, oxatomide was significantly more active than placebo at the first examination (p < 0.05 and p < 0.01). Oxatomide was well tolerated and only 2 patients complained of drowsiness which required a reduction in dosage.

CONCLUSIONS

Oxatomide, at the dose of 1 mg/kg/day, obtained a good control of respiratory symptoms.

Effects of intranasal neostigmine on oesophageal motility in man

The effects of intranasally administered neostigmine on oesophageal peristalsis and lower oesophageal sphincter tone were investigated in 21 healthy volunteers. After 30 min of basal recording of oesophageal tracings, neostigmine (3 or 5.4 mg) or the inert vehicle were given. The oesophageal recording was continued for 45-60 min after administration. Neostigmine increased the amplitude and duration of the peristaltic waves without significantly affecting conduction. Lower oesophageal sphincter tone was also increased but post-swallowing relaxation was normal. At the highest dose, the effects of neostigmine lasted 45 min or more. There were no side effects and the heart rate was only slightly slowed. The results suggest that intranasal administration of neostigmine might be clinically useful for stimulation of upper gastrointestinal tract peristalsis.

Efficacy of intranasal administration of neostigmine in myasthenic patients

The efficacy of intranasally administered neostigmine was tested in 22 patients with generalized myasthenia gravis (MG). Topical therapy to the highly vascularized oropharynx proved to be quickly effective in 5-15 min both clinically and electrophysiologically. Twenty-eight MG patients were then recruited from different centres and their morning doses of oral pyridostigmine were substituted with intranasal neostigmine over a period of 2 or 3 weeks. Intranasal neostigmine proved to be equally efficacious in this regimen. No side-effect was noted even in 4 patients treated in this way for 1 year. Intranasal administration of anti-acetylcholinesterase may be very beneficial: (1) for patients with irregular absorption of oral doses; (2) early in the morning and every time a fast and temporary effect is needed; (3) in bulbar impairment and emergencies, in which a handy atomizer may be life-saving.

Acute treatment of myasthenia gravis with intranasal neostigmine: clinical and electromyographic evaluation

The effectiveness of intranasal neostigmine (9.3-13.8 mg) was tested in 20 subjects with myasthenia gravis, classified as Osserman grades 2A and 2B. In all cases the drug produced significant clinical and electromyographic improvement. No side effects were reported during the treatment.

[Oxatomide in the treatment of pruriginous skin diseases of various nature]

A study in two parts was carried out with the aim of developing a formulation of oxatomide for topical dermatological use. During the first part of the study the safety of 4 formulations (cream and gel at 2.5% and 5%) was evaluated by means of the patch-test, while in the second a clinical trial was carried out in order to assess the anti-itching efficacy of the formulation chosen on the basis of the results of the first part (gel 5%). During the double blind study of safety, only one patient out of 33 studied showed a reaction, and with all formulations. In the second part of the study 30 patients (16 F, 14 M) were admitted, aged between 13 and 77 years (mean age 48.2) and suffering from cutaneous diseases with itching. The study was open and each subject applied oxatomide gel at 5% twice a day for 14 days. There was a subsequent follow-up without therapy of 14 days. During the study a significant (p less than 0.01 between times) improvement in lesions was observed, with an average reduction of 61% for itching, 54% for erythema, 60% for excoriations and 59% for lichenification. Acceptability and safety were good. Only one subject suspended treatment due to the onset of burning on the site of application. In the follow-up period the therapeutic results achieved were generally maintained.

[Evaluation of the inhibition of allergen-specific and nonspecific skin responses by topical oxatomide]

A double blind study against placebo was carried out in order to assess the inhibition induced by oxatomide gel in specific and aspecific cutaneous responses (prick test). Twenty allergic patients (8 M, 12 F) aged between 15 and 59 years (average 31) were treated for 7 days with oxatomide gel 5% or with placebo (2 applications a day). The results show a significant reduction of itching and of wheal size (considering either major diameter and area) only in the oxatomide group (p less than 0.01 between times and p less than 0.001 between treatments), whereas among controls itching remained unchanged and wheal size increased. During the follow-up a gradual return of wheal size to initial values in the patients treated was observed.