Trends in Tramadol

Tramadol's Inhibitory Effects on Sexual Behavior: Pharmacological Studies in Serotonin Transporter Knockout Rats

Tramadol is an effective pharmacological intervention in human premature ejaculation (PE). To investigate whether the inhibitory action of tramadol is primarily caused by its selective serotonin reuptake inhibitory (SSRI) effects we tested the dose–response effects of tramadol on sexual behavior in serotonin transporter wild type (SERT^+/+), heterozygous (SERT^+/-), and knockout (SERT^-/-) rats. To investigate whether other mechanisms contribute to the inhibitory effects, WAY100,635, a 5-HT_1A receptor antagonist and naloxone, a μ-opioid receptor antagonist, were tested on sexual behavior together with tramadol. Tramadol dose-dependently decreases sexual activity in all genotypes. In all studies, SERT^+/- rats did not respond differently from SERT^+/+ rats. WAY100,635 did not affect sexual activity in SERT^+/+, but dose-dependently reduced sexual activity in SERT^-/- rats. WAY100,635 (0.3 mg/kg) combined with tramadol (20 mg/kg) significantly reduced sexual activity in SERT^+/+ and even stronger in SERT^-/- rats. Naloxone did not affect sexual behavior consistently in SERT^+/+ rats, while in SERT^-/- rats all doses reduced ejaculation frequency mildly. Combining naloxone (20 mg/kg) and tramadol (20 mg/kg) decreased ejaculation frequencies in both genotypes. Interestingly, combining tramadol (20 mg/kg), WAY100,635 (0.3 mg/kg) and naloxone (20 mg/kg) led to complete elimination of all sexual activity in both SERT^+/+ and SERT^-/- rats. These findings suggest that the inhibitory effects of tramadol on male sexual behavior in SERT^+/+ rats is mainly, if not exclusively, due to SERT inhibition, with an important role for 5-HT_1A receptors, although influence of other systems (e.g., noradrenergic) cannot be excluded. As SSRIs exert their sexual inhibition after chronic administration, tramadol may be therapeutically attractive as “on demand” therapy for PE.

Effect of Perioperative Opioids on Cancer-Relevant Circulating Parameters: Mu Opioid Receptor and Toll-Like Receptor 4 Activation Potential, and Proteolytic Profile

Purpose: The purpose of this study is to investigate the potential interplay between opioid analgesia and tumor metastasis through modulation of μ-opioid receptor (MOR), Toll-like receptor 4 (TLR4) activation, and matrix degradation potential.Experimental Design: Plasma samples were collected from 60 patients undergoing elective lower limb joint replacement preoperatively and at 3, 6, and 24 hours after surgery; pain scores were documented at the same time points. Opioid administration was recorded and converted into morphine IV equivalents. Plasma samples were also collected from 10 healthy volunteers. Alphascreen cyclic AMP assay and MOR-overexpressing cells were employed to quantify MOR activation. HEK-Blue hTLR4 were utilized to measure TLR4 activation. Circulating matrix metalloprotease and tissue inhibitor of matrix protease activities were assessed by gelatin zymography and reverse zymography, respectively.Results: Postoperative plasma samples displayed the ability to activate MOR and to inhibit lipopolysaccharide (LPS)-induced TLR4 activation. Linear mixed model analysis revealed that MOR activation had a significant effect on inhibition of LPS-induced TLR4 activation. Furthermore, TLR4 had a significant effect to explain pain scores. Postoperative samples also displayed altered circulating matrix-degrading enzymes activity potential, but this was correlated neither to opioid administration nor to MOR activation potential.Conclusions: Our results show for the first time that (i) opioids administered to surgery patients result in modulation of ligand-induced TLR4 activation and (ii) postoperative pain is associated with increased circulating TLR4 activation potential. Our study further promotes the use of MOR activation potential rather than opioid intake in clinical studies measuring opioid exposure at a given time point. Clin Cancer Res; 24(10); 2319-27. ©2018 AACR.

When the Safe Alternative Is Not That Safe: Tramadol Prescribing in Children

Children represent a vulnerable population in which management of nociceptive pain is complex. Drug responses in children differ from adults due to age-related differences. Moreover, therapeutic choices are limited by the lack of indication for a number of analgesic drugs due to the challenge of conducting clinical trials in children. Furthermore the assessment of efficacy as well as tolerance may be complicated by children's inability to communicate properly. According to the World Health Organization, weak opioids such as tramadol and codeine, may be used in addition to paracetamol and ibuprofen for moderate nociceptive pain in both children and adults. However, codeine prescription has been restricted for the last 5 years in children because of the risk of fatal overdoses linked to the variable activity of cytochrome P450 (CYP) 2D6 which bioactivates codeine. Even though tramadol has been considered a safe alternative to codeine, it is well established that tramadol pharmacodynamic opioid effects, efficacy and safety, are also largely influenced by CYP2D6 activity. For this reason, the US Food and Drug Administration recently released a boxed warning regarding the use of tramadol in children. To provide safe and effective tramadol prescription in children, a personalized approach, with dose adaptation according to CYP2D6 activity, would certainly be the safest method. We therefore recommend this approach in children requiring chronic or recurrent nociceptive pain treatment with tramadol. In case of acute inpatients nociceptive pain management, prescribing tramadol at the minimal effective dose, in a child appropriate dosage form and after clear instructions are given to the parents, remains reasonable based on current data. In all other situations, morphine should be preferred for moderate to severe nociceptive pain conditions.

Comparision of Analgesic Efficacy of Tramadol Infusion Versus Tramadol Plus Ondansetron Infusion In Medical Intensive Care Unit

Background:

Tramadol, a preferred analgesic due to its less respiratory depression. It also has a central action that blocks the reuptake and enhances the release of serotonin at spinal antinociceptive pathways. Ondansetron, an antiemetic is a serotonin receptor antagonist. Due to the contradictory actions of the two drugs, co-administration of these drugs resulted in higher usage of tramadol. All these studies were done in the postoperative period.

Aim:

The aim of this study is to evaluate the analgesic efficacy of tramadol infusion versus tramadol plus ondansetron infusion in Medical Intensive Care Unit (ICU) patients.

Materials and Methods:

After Institutional Ethical Committee approval, 50 patients who experience pain other than postoperative pain were enrolled and randomized into two groups. Both the groups initially received 50 mg of tramadol intravenously over 10 min followed by Group T+O received 10 mg/h tramadol + 0.4 mg/h ondansetron as an infusion. Group T received 10 mg/h tramadol as infusion. Hemodynamic parameters along with pain assessment using Verbal Rating Scale (VRS) were analyzed at 0, 3, 6, 12, and 24 h. Rescue analgesia was administered if VRS >4. Side effects were noted by condition scoring criteria (CSC) scale.

Results:

Rescue analgesia was administered at 3 h, for three patients in T+O Group and 1 patient in T Group, but this is not statistically significant (P = 0.153). No rescue analgesia was required in both the groups at any other point of time. There was fall in heart rate, systolic and diastolic blood pressures, respiratory rate at 0, 3, 6, 12, and 24 h in both the groups but not statistically significant. Grade 1 sedation of CSC scale was observed in two patients of Group T+O and one patient in Group T but not statistically significant (P = 0.153). No nausea and vomiting were seen.

Conclusions:

We conclude that co-administration of tramadol and ondansetron can be practiced in medical ICU patients without any higher requirement in dosage of tramadol.

Analgesia and mouse strain influence neuromuscular plasticity in inflamed intestine

BACKGROUND

Mouse models of inflammatory bowel disease (IBD) identify an impact on the enteric nervous system (ENS) but do not distinguish between Crohn's disease and ulcerative colitis phenotypes. In these models, analgesia is required, but its influence on different strains and disease outcomes is unknown. Therefore, changes to the ENS and intestinal smooth muscle were studied in trinitrobenzene sulfonic acid (TNBS) and dextran sodium sulfate (DSS) induced colitis to identify the effects of analgesia, and compared between two mouse strains.

METHODS

Colitis was induced in CD1 or BALB/c mice receiving analgesia with either buprenorphine or tramadol. Euthanasia was on Day 8 (DSS) or Day 4 (TNBS). Outcomes were Disease Activity Index and cytokine assay, and quantitative histology and immunocytochemistry were used to evaluate effects of inflammation on neurons and smooth muscle.

KEY RESULTS

In BALB/c mice, both models of colitis caused >2-fold increase in smooth muscle cell number. DSS caused axon proliferation without neuron loss while TNBS caused significant neuron loss and axonal damage. Buprenorphine (but not tramadol) was generally anti-inflammatory in both strains, but correlated with lethal outcomes to TNBS in BALB/c mice.

CONCLUSIONS AND INFERENCES

Smooth muscle growth is common to both models of colitis. In contrast, ENS damage in TNBS is correlated with the severe response of a Crohn's disease-like phenotype, while DSS correlates with a milder, ulcerative colitis-like outcome in the deeper tissues. Analgesia with tramadol over buprenorphine is supported for mouse studies of IBD.

Publication-Based Academic Interest in Drugs and Techniques for Treatment of Postoperative Pain, 1975-2015

PURPOSE

The aim of this study was to determine how drugs and their administration techniques, introduced over the past 40 years and still popular now, influenced publication-based academic interest in the treatment of postoperative pain.

METHODS

Specific scientometric indices-popularity index (PI), top journal selectivity index (TJSI), and index of change (IC)-were used. Of the 61 terms searched, only those that had a PI value ≥1.0 during the 2011-2015 period were selected. They include eight drugs-bupivacaine, fentanyl, ropivacaine, acetaminophen, tramadol, remifentanil, and dexamethasone-and five techniques-patient-controlled analgesia, epidural opioids, ultrasound-guided nerve blocks, continuous nerve blocks, and transversus abdominis plane block (presented according to their decreasing PI value in each category).

RESULTS

Four of these drugs or techniques with the highest PI in 2011-2015 also held top positions even 20 years earlier: in 1991-1995, the PI for bupivacaine was 9.1; fentanyl, 6.6; patient-controlled analgesia, 10.4; and epidural opioids, 6.8. Since that time, their PI values slowly decreased, for the first three items by approximately 50% and much more than that (85%) with epidural opioids. Nevertheless, to this day, they continue to hold the highest degree of publication-based academic interest. The TJSI can be regarded as an index of expectations at the time of articles publication. With bupivacaine, fentanyl, patient-controlled analgesia, and epidural opioids, the TJSI exceeded the specific high threshold of 10.0 for a very long time. The TJSIs of acetaminophen, ketamine, and dexamethasone were increased with the advent of new expectations regarding the treatment of postoperative pain using these old agents.

CONCLUSIONS

Two important developments related to ultrasound-guided nerve block and continuous nerve block demonstrated only a moderate degree of academic interest. In conclusion, even today, the greatest publication-based academic interest related to postoperative pain is associated with drugs and techniques introduced 40-50 years ago.

Advanced Analgesic Drug Delivery and Nanobiotechnology

Transdermal administration of analgesic medications offers several benefits over alternative routes of administration, including a decreased systemic drug load with fewer side effects, and avoidance of drug degradation by the gastrointestinal tract. Transdermal administration also offers a convenient mode of drug administration over an extended period of time, particularly desirable in pain medicine. A transdermal administration route may also offer increased safety for drugs with a narrow therapeutic window. The primary barrier to transdermal drug absorption is the skin itself. Transdermal nanotechnology offers a novel method of achieving enhanced dermal penetration with an extended delivery profile for analgesic drugs, due to their small size and relatively large surface area. Several materials have been used to enhance drug duration and transdermal penetration. The application of nanotechnology in transdermal delivery of analgesics has raised new questions regarding safety and ethical issues. The small molecular size of nanoparticles enables drug delivery to previously inaccessible body sites. To ensure safety, the interaction of nanoparticles with the human body requires further investigation on an individual drug basis, since different formulations have unique properties and side effects.