Abuse liability, behavioral pharmacology, and physical-dependence potential of opioids in humans and laboratory animals: lessons from tramadol

A novel tramadol-polycaprolactone implant could palliate heroin conditioned place preference and withdrawal in rats: behavioral and neurochemical study

Drug dependence is a chronic brain disease characterized by craving and recurrent episodes of relapse. Tramadol HCl is a promising agent for withdrawal symptoms management, considering its relatively low abuse potential and safety. Oral administration, however, is not preferred in abstinence maintenance programs. Introducing an implantable, long-lasting formula is suggested to help outpatient abstinence programs achieve higher rates of treatment continuation. Tramadol implants (T350 and T650) were prepared on polycaprolactone polymer ribbons by the wet method. Male Wistar rats were adapted to heroin-conditioned place preference (CPP) at escalating doses (3-30 mg/kg, intraperitoneally, for 14 days). Implants were surgically implanted in the back skin of rats. After 14 days, the CPP score was recorded. Naloxone (1 mg/kg, intraperitoneally) was used to induce withdrawal on day 15, and symptoms were scored. Elevated plus maze and open field tests were performed for anxiety-related symptoms. Striata were analyzed for neurochemical changes reflected in dopamine, 3,4-dihydroxyphenyl acetic acid, gamma-aminobutyric acid, and serotonin levels. Brain oxidative changes including glutathione and lipid peroxides were assessed. The tramadol implants (T350 and T650) reduced heroin CPP and limited naloxone-induced withdrawal symptoms. The striata showed increased levels of 3,4-dihydroxyphenyl acetic acid, and serotonin and decreased levels of gamma-aminobutyric acid and dopamine after heroin withdrawal induction, which were reversed after implanting T350 and T650. Implants restore the brain oxidative state. Nonsignificant low naloxone-induced withdrawal score after the implant was used in naive subjects indicating low abuse potential of the implants. The presented tramadol implants were effective at diminishing heroin CPP and withdrawal in rats, suggesting further investigations for application in the management of opioid withdrawal.

Exploring the potential use of melatonin as a modulator of tramadol-induced rewarding effects in rats

Background

Melatonin is responsible for regulating the sleep-wake cycle and circadian rhythms in mammals. Tramadol, a synthetic opioid analgesic, is used to manage moderate to severe pain but has a high potential for abuse and dependence. Studies have shown that melatonin could be a potential modulator to reduce tramadol addiction.

Methods

Male Wistar rats were used to investigate the effect of melatonin on tramadol-induced place preference. The rats were divided into four groups: control, tramadol, tramadol + melatonin (single dose), and tramadol + melatonin (repeated doses). Tramadol was administered intraperitoneally at 40 mg/kg, while melatonin was administered at 50 mg/kg for both the single dose and repeated-dose groups. The study consisted of two phases: habituation and acquisition.

Results

Tramadol administration produced conditioned place preference (CPP) in rats, indicating rewarding effects. However, melatonin administration blocked tramadol-induced CPP. Surprisingly, repeated doses of melatonin were ineffective and did not reduce the expression of CPP compared to that of the single dose administration.

Conclusion

The study suggests that melatonin may be a potential therapeutic option for treating tramadol addiction. The results indicate that melatonin attenuates the expression of tramadol-induced CPP, supporting its uses as an adjunct therapy for managing tramadol addiction. However, further studies are needed to investigate its effectiveness in humans.

Reinforcing effect of tramadol in the rat

Tramadol is one of the most commonly prescribed analgesic opioids in various pharmacopeias. Tramadol has been linked to abuse in recent clinical investigations. However, the behavioral effects and neural substrates of the drug have not been well characterized in preclinical studies. As a result, the present study investigated the effects of tramadol on behavioral sensitizations in rats. Its impacts on cellular and molecular alterations in the brain were also investigated. In conditioned place preference (CPP) paradigm, tramadol induced behavioral as well as motor sensitizations. These effects were dramatically reduced by intraperitoneal administration of naltrexone, an opioid receptor antagonist. Tramadol caused changes in several molecular markers (pERK1/2, Δ-FosB, PKCγ, PKMζ GAD67) in the anterior cingulate cortex, which could indicate an increase in excitation within this structure. Tramadol is demonstrated in the present study to be a reinforcing drug in rats, as it increased both behavioral and motor sensitizations. Tramadol's effects are most likely due to the high levels of excitation it causes in the brain, which is mostly caused by the activation of opioid receptors.

Tramadol and Tapentadol Induce Conditioned Place Preference with a Differential Impact on Rewarding Memory and Incubation of Craving

Tramadol and tapentadol, synthetic opioids commonly prescribed for moderate-to-severe pain, have a unique pharmacology that optimizes their analgesia and safety. However, they are not devoid of risks, presenting addictive, abuse, and dependence potential. While tramadol-reinforcing properties have been documented by various studies with human and animal models, including conditioned place preference (CPP) assays, no similar studies have been performed with tapentadol. In the present study, we performed CPP assays by intraperitoneally administering Wistar rats with a tramadol/tapentadol therapeutic dose. Animal permanence and the number of entries in the CPP compartments were recorded in the preconditioning phase and then 1 (T1), 7 (T7), and 14 (T14) days after conditioning. Both opioids induced a change in place preference (T1), suggesting that they have short-term reinforcing properties. However, only tramadol was associated with place preference retention (T7 and T14), with an increase in the number of entries in the opioid-paired compartment (T1 and T7), showing that it causes rewarding memory and incubation of craving. The results indicate that at therapeutic doses: (1) both drugs cause short-term rewarding effects and (2) as opposed to tramadol, tapentadol does not cause CPP retention, despite its higher central nervous system activity and stricter scheduling.

Mu-opioid receptor and receptor tyrosine kinase crosstalk: Implications in mechanisms of opioid tolerance, reduced analgesia to neuropathic pain, dependence, and reward

Despite the prevalence of opioid misuse, opioids remain the frontline treatment regimen for severe pain. However, opioid safety is hampered by side-effects such as analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, or reward. These side effects promote development of opioid use disorders and ultimately cause overdose deaths due to opioid-induced respiratory depression. The intertwined nature of signaling via μ-opioid receptors (MOR), the primary target of prescription opioids, with signaling pathways responsible for opioid side-effects presents important challenges. Therefore, a critical objective is to uncouple cellular and molecular mechanisms that selectively modulate analgesia from those that mediate side-effects. One such mechanism could be the transactivation of receptor tyrosine kinases (RTKs) via MOR. Notably, MOR-mediated side-effects can be uncoupled from analgesia signaling via targeting RTK family receptors, highlighting physiological relevance of MOR-RTKs crosstalk. This review focuses on the current state of knowledge surrounding the basic pharmacology of RTKs and bidirectional regulation of MOR signaling, as well as how MOR-RTK signaling may modulate undesirable effects of chronic opioid use, including opioid analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, and reward. Further research is needed to better understand RTK-MOR transactivation signaling pathways, and to determine if RTKs are a plausible therapeutic target for mitigating opioid side effects.

A Machine-Learning Algorithm to Predict the Likelihood of Prolonged Opioid Use Following Arthroscopic Hip Surgery

PURPOSE

To develop a machine-learning algorithm and clinician-friendly tool predicting the likelihood of prolonged opioid use (>90 days) following hip arthroscopy.

METHODS

The Military Data Repository was queried for all adult patients undergoing arthroscopic hip surgery between 2012 and 2017. Demographic, health history, and prescription records were extracted for all included patients. Opioid use was divided into preoperative use (30-365 days before surgery), perioperative use (30 days before surgery through 14 days after surgery), postoperative use (14-90 days after surgery), and prolonged postoperative use (90-365 days after surgery). Six machine-learning algorithms (Naïve Bayes, Gradient Boosting Machine, Extreme Gradient Boosting, Random Forest, Elastic Net Regularization, and artificial neural network) were developed. Area under the receiver operating curve and Brier scores were calculated for each model. Decision curve analysis was applied to assess clinical utility. Local-Interpretable Model-Agnostic Explanations were used to demonstrate factor weights within the selected model.

RESULTS

A total of 6,760 patients were included, of whom 2,762 (40.9%) filled at least 1 opioid prescription >90 days after surgery. The artificial neural network model showed superior discrimination and calibration with area under the receiver operating curve = 0.71 (95% confidence interval 0.68-0.74) and Brier score = 0.21 (95% confidence interval 0.20-0.22). Postsurgical opioid use, age, and preoperative opioid use had the most influence on model outcome. Lesser factors included the presence of a psychological comorbidity and strong history of a substance use disorder.

CONCLUSIONS

The artificial neural network model shows sufficient validity and discrimination for use in clinical practice. The 5 identified factors (age, preoperative opioid use, postoperative opioid use, presence of a mental health comorbidity, and presence of a preoperative substance use disorder) accurately predict the likelihood of prolonged opioid use following hip arthroscopy.

LEVEL OF EVIDENCE

III, retrospective comparative prognostic trial.

Early Optimized Pharmacological Treatment in Patients With Depression and Chronic Pain

Major depressive disorder (MDD) is the leading cause of disability worldwide. Patients with MDD have high rates of comorbidity with mental and physical conditions, one of which is chronic pain. Chronic pain conditions themselves are also associated with significant disability, and the large number of patients with MDD who have chronic pain drives high levels of disability and compounds healthcare burden. The management of depression in patients who also have chronic pain can be particularly challenging due to underlying mechanisms that are common to both conditions, and because many patients with these conditions are already taking multiple medications. For these reasons, healthcare providers may be reluctant to treat such patients. The Canadian Network for Mood and Anxiety Treatments (CANMAT) guidelines provide evidence-based recommendations for the management of MDD and comorbid psychiatric and medical conditions such as anxiety, substance use disorder, and cardiovascular disease; however, comorbid chronic pain is not addressed. In this article, we provide an overview of the pathophysiological and clinical overlap between depression and chronic pain and review evidence-based pharmacological recommendations in current treatment guidelines for MDD and for chronic pain. Based on clinical experience with MDD patients with comorbid pain, we recommend rapidly and aggressively treating depression according to CANMAT treatment guidelines, using antidepressant medications with analgesic properties, while addressing pain with first-line pharmacotherapy as treatment for depression is optimized. We review options for treating pain symptoms that remain after response to antidepressant treatment is achieved.

The Influence of Tramadol on Intravaginal Ejaculatory Latency Time and Sexual Satisfaction Score in Treating Patients With Premature Ejaculation: A Network Meta-Analysis

This network meta-analysis aimed at assessing the influence of tramadol on the intravaginal ejaculatory latency time (IELT) and sexual satisfaction score (SSS) in treating patients with premature ejaculation (PE). The PubMed, Embase, Cochrane Library databases (until July 2021), and original references of the included articles was systematically retrieved. The PRISMA checklist was followed. Finally, 14 articles including 1971 patients were included in this analysis. The results indicated that patients who were treated with tramadol (50 mg, 62 mg, 89 mg, and 100 mg) were superior to those treated with placebo in terms of IELT (p = .003, p < .00001, p < .00001, and p < .00001, respectively), but 25 mg tramadol did not show a significant advantage (p = .06). Patients who were treated with tramadol (50 mg and 100 mg) had a better efficacy than who were treated with 25 mg tramadol in the IELT (p < .00001 and p < .00001), but the effect of 50 mg tramadol and 100 mg tramadol were not significantly different (p = .17). The tramadol group had the better effect than the placebo group in the SSS (p < .0001). And 50 mg tramadol showed a significant improvement compared with 20 mg paroxetine, as assessed by the IELT (p = .03) and SSS (p = .03). Safety assessments including adverse events suggested that tramadol was well tolerated. Tramadol showed a better improvement of IELT and SSS than placebo or paroxetine, and 50 mg tramadol may be a more reasonable therapeutic dose for patients with PE.

Fentanyl-related substance scheduling as an effective drug control strategy

Fentanyl is now the primary driver of the current opioid crisis. Fentanyl and its analogues are subject to the Controlled Substances Act of 1970, the Controlled Substances Analogue Enforcement Act of 1986 (Federal Analogue Act), state laws, international treaties, and the laws of foreign countries. The appearance of novel psychoactive substances led to further legislative developments in scheduling. New fentanyl analogues proliferated in a manner previously unseen since about 2016. Overdose deaths of these fentanyl analogues prompted the Drug Enforcement Administration to reactively emergency schedule each new fentanyl analogue as it appeared. The international community also acted. Finally, on February 6, 2018, a proactive temporary (emergency) class-wide scheduling of fentanyl-related substances was implemented based upon the fentanyl core structure to save lives. This action spurred a similar action in China. Fentanyl analogues fell dramatically in the marketplace, despite further increases in fentanyl itself. Congress temporarily extended this scheduling, but it will soon expire. Opposition to permanent class-wide was lodged due to concerns over law enforcement overreach, inadequate Health and Human Services input, and hindrance of research. This paper reaffirms the importance of a class-based scheduling strategy while also arguing for increased research of schedule I controlled substances.

Dynamic Distribution and Postmortem Redistribution of Tramadol in Poisoned Rats

In the past dozen years, the cases of tramadol intoxication have become frequent in many countries. Most previous studies focused on tramadol's pharmacology, such as pharmacokinetics, pharmacodynamics and pharmacogenetics. However, the dynamic distribution and postmortem redistribution (PMR) of tramadol remain unclear. Our study aimed to investigate these two issues systematically in various specimens of 216 poisoned male rats. A validated gas chromatography-mass spectrometry method was used in this study to measure the concentrations of tramadol. In the first part, 66 tramadol poisoned rats were sacrificed at 11 different time points and their organs were collected separately for the study of tramadol's dynamic distribution, which made it feasible to investigate its PMR later on. The results of this part showed that tramadol's concentrations varied according to the organ and time, and peaked 2 h after intragastric administration in the specimens of liver, kidney, spleen, lung, brain and heart-blood (except stomach and heart). Based on the results of the first part, the concentration of tramadol peaked 2 h in most tissues. Therefore, this time point was used for the study of tramadol's PMR. In the second part, the remaining 150 rats were sacrificed 2 h after intragastric administration of tramadol, and the carcasses were stored under three different conditions (-20, 4 and 20°C). The autopsy was carried out at eight different time points and their organs were collected separately. The results of this part showed that under storage temperatures of -20 and 4°C, the concentrations of tramadol in individual organs showed no significant changes at different time points whereas under a storage temperature of 20°C, the concentrations in certain organs (liver, kidney, spleen, lung, brain and heart-blood) increased significantly at the last few time points. PMR of tramadol was therefore confirmed. The process of PMR of tramadol could be slowed or stopped at lower storage temperatures (-20 or 4°C), which is significant in cases of suspected tramadol poisoning.

Cognitive impairment in patients diagnosed with tramadol dependence compared to healthy controls

Cognitive impairment is one of the consequences of substance use. We aimed to estimate the prevalence and correlates of cognitive impairment among patients with tramadol dependence in comparison with healthy controls. The sample consisted of 30 patients with tramadol dependence and 30 healthy controls. Cognitive functions were assessed using Benton Visual Retention Test- revised, Trail Making Test A and B and Wechsler Memory Scale. Patients were also subjected to the Structured Clinical Interview for diagnostic and statistical manual of mental disorders-fourth edition (DSM-IV) Axis I Disorder, the Structured Clinical Interview for DSM-IV Axis II Disorders and the Addiction Severity Index. Results showed that tramadol-dependence patients performed significantly worse than controls regarding cognitive functions, mainly manifested in impaired visual memory, visual reconstruction ability and processing, delayed memory, attention and processing speed, and visual, auditory, immediate, delayed and working memory. We found a nonsignificant negative correlation between cognitive performance and the age of patients or duration of tramadol use. Patients with tramadol dependence were more likely to have cognitive impairment than controls. This may have important clinical implications in determining the right academic and vocational programs for these individuals and adding skills training (e.g. problem solving) to their standard psychosocial treatment.

Enhancement in antinociceptive and anti-inflammatory effects of tramadol by transdermal proniosome gel

Oral therapy of tramadol, an opiate analgesic, undergoes extensive hepatic metabolism and requires frequent administration. Transdermal therapy by virtue can overcome these issues and can improve the efficacy and reduce abuse liability of tramadol. The aim of this research was to investigate the possibility of transdermal delivery of tramadol by formulating proniosome gel and evaluate its therapeutic potential in vivo. The effect of formulation composition as well as amount of drug on physicochemical characteristics of prepared proniosomes were examined. Best proniosome gel (F4) was selected and evaluated for drug release, stability and transdermal efficacy by ex vivo and in vivo experiments. The vesicles demonstrated optimal properties including spherical shape, nanosize with good entrapment efficiency, adequate zeta potential, higher stability and greater transdermal flux. The amorphization and dispersion of tramadol in the aqueous core of proniosome vesicles was confirmed by differential scanning calorimeter. Release profile of F4 was distinct (P < 0.001) from control and displayed steady and prolonged tramadol release by Fickian diffusion. Transdermal therapy of F4 showed prominent reduction of induced twitches (P < 0.005) in mice and edema (P < 0.05) in rats, as compared to oral tramadol. The improvement in clinical efficacy of tramadol in transdermal therapy is correlated with the pharmacokinetic data observed. In conclusion, the observed improvement in antinociceptive and anti-inflammatory effects from proniosome carriers signifies its potential to be a suitable alternative to oral therapy of tramadol with greater efficacy.

Efficacy and Safety of Intravenous Tramadol versus Intravenous Paracetamol for Relief of Acute Pain of Primary Dysmenorrhea: A Randomized Controlled Trial

INTRODUCTION

Many pharmaceutical, surgical, and complementary medical interventions are used for primary dysmenorrhea treatment. However, no consensus has been reached about the most effective intervention.

OBJECTIVE

To compare the efficacy and safety of IV tramadol versus IV paracetamol in relieving acute pain of primary dysmenorrhea.

METHODS

This randomized controlled trial was conducted in a tertiary referral hospital and included 100 patients between 18 and 35 years old diagnosed with primary dysmenorrhea. Patients received either 1-g paracetamol or 100-mg tramadol in 100-mL normal saline as an IV infusion over 10 min. Pain intensity was measured by using a visual analog scale at 15, 30, 60 min, and 2 h. We recorded drug side effects and requirements for rescue analgesics.

RESULTS

Pain scores were significantly lower in the tramadol group compared with the paracetamol group at 15, 30, 60 min, and 2 h (p < 0.001). Fewer patients in the tramadol group needed rescue analgesics compared with the paracetamol group (p = 0.04). No significant differences were reported in side effects between both groups.

CONCLUSIONS

IV tramadol is superior to IV paracetamol in relieving acute pain of primary dysmenorrhea with a comparable side effect profile.

Preoperative Pain Management: Is Tramadol a Safe Alternative to Traditional Opioids Before Total Hip Arthroplasty?

BACKGROUND

Preoperative opioid use has been associated with worse clinical outcomes and higher rates of prolonged opioid use following lower extremity arthroplasty. Tramadol has been recommended for management of osteoarthritis-related pain; however, outcomes following total hip arthroplasty (THA) in patients taking tramadol in the preoperative period have not been well described. The aim of this study is to examine the effect of preoperative tramadol use on postoperative outcomes in patients undergoing elective THA.

METHODS

A total of 5304 patients who underwent primary THA for degenerative hip pathology from 2008 to 2014 were identified using the Humana Claims Database. Patients were grouped by preoperative pain management modality into 3 mutually exclusive populations including tramadol, traditional opioid, or nonopioid only. A multivariate logistic regression was used to evaluate all postsurgical outcomes of interest.

RESULTS

Tramadol users had an increased risk of developing prolonged narcotic use (odds ratio [OR], 2.17; confidence interval [CI], 1.89-2.49; P < .001) following surgery compared to nonopioid-only users. When compared to traditional opioid use, tramadol use was associated with decreased risk of subsequent 90-day minor medical complications (OR, 0.75; CI, 0.62-0.90; P = .002), emergency department visits (OR, 0.70; CI, 0.57-0.85; P < .001), and prolonged narcotic use (OR, 0.43; CI, 0.37-0.49; P < .001). Traditional opioid use significantly increased length of stay by 0.20 days (P = .001) when compared to tramadol use.

CONCLUSION

Preoperative tramadol use is associated with prolonged opioid use following THA but is not associated with other postoperative complications. Patients taking tramadol preoperatively appear to have a lower risk of postoperative complications compared to patients taking traditional opioids preoperatively.

Opioid Stewardship in Orthopaedic Surgery: Principles and Practice

The abuse of prescription opioid pain medication has contributed to the U.S. opioid crisis. Opioid stewardship programs ensure that our patients receive the safest and most effective opioid regimens. Opioid stewardship programs involve a multidisciplinary team, including pharmacists, orthopaedic surgeons, nurses, pain management personnel, and anesthesiologists. All of these stakeholders work together to formulate the best evidence-based use of these medications.

Preclinical assessment of tramadol abuse potential: Effects of acute and repeated tramadol on intracranial self-stimulation in rats

BACKGROUND

Tramadol is a widely used analgesic that activates mu-opioid receptors (MOR) and inhibits serotonin and norepinephrine transporters. This mixed pharmacology may limit both its own abuse potential and its modulation of abuse potential of other MOR agonists.

AIMS

This study used an intracranial self-stimulation (ICSS) procedure to compare abuse-related effects produced by acute or repeated treatment with tramadol or morphine in rats. Abuse potential in ICSS procedures is indicated by a drug-induced increase (or 'facilitation') of ICSS responding.

METHODS

Adult male Sprague-Dawley rats were implanted with electrodes targeting the medial forebrain bundle and trained to respond on a lever for pulses of electrical brain stimulation. Tramadol effects were evaluated after acute administration (3.2-32 mg/kg) in the absence or presence of the opioid antagonist naltrexone, the CYP2D6 hepatic-enzyme inhibitor quinine or a combination of both. Additionally, both tramadol and morphine were also tested before and after repeated tramadol (32 mg/kg/day for six days) or repeated morphine (3.2 mg/kg/day for six days).

RESULTS

Acute tramadol produced primarily ICSS rate-decreasing effects that were antagonised by naltrexone but not by quinine or naltrexone + quinine. Tramadol also produced little or no ICSS facilitation after repeated tramadol or repeated morphine, and repeated tramadol did not enhance ICSS facilitation by morphine. By contrast, morphine-induced ICSS facilitation was enhanced by repeated morphine treatment.

CONCLUSIONS

These results suggest that tramadol has lower abuse potential than other abused MOR agonists and that repeated tramadol exposure produces relatively little enhancement of abuse potential of other MOR agonists.

Tramadol for the Management of Opioid Withdrawal: A Systematic Review of Randomized Clinical Trials

The increase in the prescription of opioid medications has resulted in a wildfire of misuse of opioids, both for medical and non-medical reasons, with over 1.7 million people in the United States (US) suffering from distinct disorders owing to opioid use. While various medications, such as methadone, buprenorphine, and naloxone, among others, have been used in treating opioid withdrawal symptoms, concerns of the potential abuse of these drugs, the cost of procurement, legislations, and prescription policies have risen. In recent times, tramadol has been considered a viable replacement for some of these treatment regimes. Tramadol is a synthetic analgesic that acts centrally, possessing opioid-like effects due to the binding of its metabolite with the mu (µ)-opioid receptor, yet with low potential for abuse. Several clinical studies conducted in the past ten years have identified the effects of tramadol in opioid withdrawal cases. The results showed that it exhibits better efficacy and tolerance with fewer side effects in specific clinical scenarios as compared to existing available detox management. We aim to examine the properties of tramadol in opioid withdrawal through this systematic review of clinical studies on humans.

Why are we still using opioids for osteoarthritis?

Osteoarthritis is a common debilitating condition affecting a substantial portion of the population and is an accepted consequence of ageing and overuse. Whilst surgical interventions are a definitive approach, most cases are managed medically with analgesia. Pharmacological therapies have included acetaminophen, non-steroidal anti-inflammatory drugs and opiates. Although significant controversies exist in the use of opioids for chronic musculoskeletal pain, many leading guidelines continue to recommend its use despite increasing evidence to suggest an increase in addiction, morbidity and mortality. With the opiate crisis growing, we re-examine the role opiates have in this chronic condition and current data, and briefly evaluate alternative therapies.

Desmetramadol Has the Safety and Analgesic Profile of Tramadol Without Its Metabolic Liabilities: Consecutive Randomized, Double-Blind, Placebo- and Active Comparator-Controlled Trials

Desmetramadol is an investigational analgesic consisting of (+) and (-) enantiomers of the tramadol metabolite O-desmethyltramadol (M1). Tramadol is racemic and exerts analgesia by monoaminergic effects of (-)-tramadol and (-)-M1, and by the opioid (+)-M1. Tramadol labeling indicates cytochrome P450 (CYP) isozyme 2D6 ultrarapid metabolizer can produce dangerous (+)-M1 levels, and CYP2D6 poor metabolizers insufficient (+)-M1 for analgesia. We hypothesized that desmetramadol could provide the safety and analgesia of tramadol without its metabolic liabilities. We conducted consecutive double-blind, randomized, placebo-controlled, 3 segment cross-over trials A and B to investigate the steady-state pharmacokinetics and analgesia of 20 mg desmetramadol and 50 mg tramadol in 103 healthy participants without (n = 43) and with (n = 60) cotreatment with the CYP inhibitor paroxetine. In the absence of CYP inhibition (trial A), 20 mg desmetramadol and 50 mg tramadol dosed every 6 hours gave equivalent steady-state (+)-M1, similar adverse events, and analgesia significantly greater than placebo, but equal to each other. In trial B, CYP inhibition significantly depressed tramadol steady-state (+)-M1, reduced its adverse events, and led to insignificant analgesia comparable with placebo. In contrast, CYP inhibition in trial B had no deleterious effect on desmetramadol (+)-M1 or (-)-M1, which gave significant analgesia as in trial A and superior to tramadol (P = .003). Desmetramadol has the safety and efficacy of tramadol without its metabolic liabilities. CLINICALTRIALS.GOV REGISTRATIONS: NCT02205554, NCT03312777 PERSPECTIVE: To our knowledge, this is the first study of desmetramadol in humans and the first to show it provides the same safety and analgesia as tramadol, but without tramadol's metabolic liabilities and related drug-drug interactions. Desmetramadol could potentially offer expanded safety and usefulness to clinicians seeking an alternative to schedule II opioids.

Use of Tramadol for Management of Opioid Use Disorders: Rationale and Recommendations

Opioids are one of the most common illicit psychoactive substances being used in India. In fact, opioid use disorders are the most common disorder presenting to the substance use disorder treatment centers across the country. Effective and evidence-based interventions are available for management of opioid use disorders. However, the treatment for opioid use disorders remains difficult to access for most of those in need in India. The current article presents the literature on the use of tramadol for the management of opioid use disorders. It also makes recommendations on the use of tramadol for the management of opioid use disorders. Tramadol offers a viable alternative to the existing options for the management of opioid use disorders. It has been found effective when used for this indication. It offers certain major advantages such as easy and wide availability and low abuse liability. It offers a good option to expand the treatment services for opioid use disorders across the country.

Enhanced recovery in liver surgery decreases postoperative outpatient use of opioids

BACKGROUND

Pathways of enhanced recovery in liver surgery decrease inpatient opioid use; however, little data exist regarding their effect on discharge prescriptions and post-discharge opioid intake.

METHODS

For consecutive patients undergoing liver resection from 2011-2018, clinicopathologic factors were compared between patients exposed to enhanced recovery vs. traditional care pathways. Multivariable analysis was used to determine factors predictive for traditional opioid use at the first postoperative follow-up. The enhanced recovery in liver surgery protocol included opioid-sparing analgesia, goal-directed fluid therapy, early postoperative feeding, and early ambulation.

RESULTS

Of 244 cases, 147 enhanced recovery patients were compared with 97 traditional pathway patients. Enhanced recovery patients were older (median 57 years vs 52 years, P = .031) and more frequently had minimally invasive operations (37% vs 16%, P < .001), with fewer major complications (2% vs 9%, P = .011). Enhanced recovery patients were less likely to be discharged with a prescription for traditional opioids (26% vs 79%, P < .001) and less likely to require opioids at their first postoperative visit (19% vs 61%, P < .001) despite similarly low patient-reported pain scores (median 2/10 both groups, P = .500). On multivariable analysis, the traditional recovery pathway was independently associated with traditional opioid use at the first follow-up (odds ratio 6.4, 95% confidence interval 3.5-12.1; P < .001).

CONCLUSION

The implementation of an enhanced recovery in liver surgery pathway with opioid-sparing techniques was associated with decreased postoperative discharge prescriptions for opioids and outpatient opioid use after oncologic liver surgery, while achieving the same level of pain control. For this and other populations at risk of persistent opioid use, enhanced recovery strategies can eliminate excess availability of opioids.

Severe complications of tramadol overdose in Iran

OBJECTIVES

Severe complications of tramadol overdose have been reported; however, few large-scale studies have investigated this issue. Therefore, this study aimed to explore the presentation and complications of tramadol overdose in patients admitted to an intoxication referral center in northwestern Iran.

METHODS

Patients with tramadol overdose admitted to Sina Teaching Hospital in Tabriz, Iran during 2013-2017 were included. For each patient, the following data were collected: demographics, previous drug or medication overdose, whether the patient was in the process of quitting drug use, ingested dose of tramadol and co-ingestants, Glasgow Coma Scale (GCS) score, clinical symptoms at the time of admission, and admission characteristics. Serotonin toxicity was diagnosed in patients who fit the Hunter criteria. Multiple logistic regression was performed to identify variables associated with the incidence of severe complications of tramadol overdose.

RESULTS

In total, 512 cases of tramadol overdose were evaluated, of which 359 patients were included, with a median age of 41 years (range, 16-69) and a median tramadol dose of 1,500 mg (range, 500-4,000). The most frequent complications associated with tramadol overdose were hypertension (38.4%), tachycardia (24.8%), and seizure (14.5%). No serotonin toxicity was detected in patients. Having a GCS score <15, having taken a tramadol dose of >1,000 mg, being in the process of quitting drug use, being 30-49 years old, and male sex were significantly related to the incidence of severe complications of tramadol overdose.

CONCLUSIONS

Although seizure was prevalent among Iranian patients with tramadol poisoning, serotonin toxicity and cardiogenic shock were rare findings.

Revisiting Tramadol: A Multi-Modal Agent for Pain Management

Tramadol-an atypical opioid analgesic-has a unique pharmacokinetic and pharmacodynamic profile, with opioidergic, noradrenergic, and serotonergic actions. Tramadol has long been used as a well-tolerated alternative to other drugs in moderate pain because of its opioidergic and monoaminergic activities. However, cumulative evidence has been gathered over the last few years that supports other likely mechanisms and uses of tramadol in pain management. Tramadol has modulatory effects on several mediators involved in pain signaling, such as voltage-gated sodium ion channels, transient receptor potential V1 channels, glutamate receptors, α₂-adrenoceptors, adenosine receptors, and mechanisms involving substance P, calcitonin gene-related peptide, prostaglandin E₂, and proinflammatory cytokines. Tramadol also modifies the crosstalk between neuronal and non-neuronal cells in peripheral and central sites. Through these molecular effects, tramadol could modulate peripheral and central neuronal hyperexcitability. Given the broad spectrum of molecular targets, tramadol as a unimodal analgesic relieves a broad range of pain types, such as postoperative, low back, and neuropathic pain and that associated with labor, osteoarthritis, fibromyalgia, and cancer. Moreover, tramadol has anxiolytic, antidepressant, and anti-shivering activities that could improve pain management outcomes. The aim of this review was to address these issues in the context of maladaptive physiological and psychological processes that are associated with different pain types.

[Consensus statement on the use of acetaminophen/tramadol in patients with moderate-severe pain]

OBJECTIVES

To present recommendations on the use of the paracetamol/tramadol (P/T) combination in patients with moderate-intense pain based on best evidence and experience.

METHODS

The method of nominal groups and Delphi was followed, and supported by a systematic literature review (SLR). A multidisciplinary panel of 12 experts in pain management was selected. In the first nominal group meeting, the aim, scope, users, and sections of the consensus document, were defined, along with the preliminary general recommendations. For the SLR, the inclusion and exclusion criteria, as well as the search strategies, were defined. Two reviewers selected and analysed the articles. This evidence was discussed in a second nominal group meeting, and definitive recommendations were developed. For each recommendation, the evidence levels and grade of recommendation grades were classified according to the Oxford model, and the grade according to the Delphi technique. It was defined as an agreement if at least 70% of the participants scored ≥7 for each recommendation (1=total disagreement to 10=total agreement).

RESULTS

A total of 20 recommendations were produced, which covered general aspects, such as the assessment of pain, and those specific to P/T management. These latter included the indications of the P/T combination (patient profile, dosing, prescription, formulations), risk management (contraindications, precautions, interactions, concomitant use with other medications, follow-up, special situations), and patient education.

CONCLUSIONS

These recommendations attempt to resolve any of the routine clinical questions, and help in the making of decisions on the use of the P/T combination in patients with moderate-intense pain.

A Systematic Review of Laboratory Evidence for the Abuse Potential of Tramadol in Humans

Background: Tramadol is an opioid-analgesic that has shown epidemiological evidence of abuse. This review evaluates the evidence for tramadol abuse potential in humans. Methods: A systematic literature search for human abuse liability examinations of tramadol was conducted in September 2018 and yielded 13 total studies. Studies were all within-subject, double-blind, placebo-controlled human laboratory comparisons of tramadol to opioid comparators. Results are organized based upon the route of tramadol administration (oral, parenteral) and the participant population (persons with and without current opioid physical dependence). Outcomes were categorized into self-report ratings of positive and negative effects, observer-ratings of effects, time course of effects, likelihood tramadol was identified as an opioid, and tramadol self-administration. Results: Results indicated the relative abuse potential of tramadol was lower than the opioids to which it was compared. Tramadol produced highest positive effect ratings when administered orally to persons with no opioid physical dependence. Relative to other opioids, it produced substantial negative ratings, generally demonstrated a slower onset of effects, and was less likely to be identified by participants as an opioid, though it did produce a higher rate of self-administration relative to other opioids in the one study reporting that outcome. Results suggest that the abuse potential of tramadol is highest when it is administered orally to non-dependent individuals, and that it likely decreases as the dose increased and when it was administered parentally or to persons with opioid physical dependence. Conclusion: Taken together, individuals may be less likely than with other opioids to escalate tramadol doses, transition from oral to parenteral routes of administration, or continue using tramadol once opioid physical dependence develops. In that way, the human abuse potential of tramadol appears to be different from and lower than other opioid analgesic medications.

An overview of tramadol and its usage in pain management and future perspective

Patients with chronic non-malignant pain report impairment of physical and social life along with psychological state affecting their overall quality of life. The purpose of managing pain is to reduce the trauma and improve the patient comfort with better quality of life. Tramadol is a centrally acting weak μ-opioid receptor analgesic and is a racemic mixture of (+)-tramadol and (-)-tramadol enantiomers. Tramadol is used worldwide and is listed in many medical guidelines for pain management. The (+)-tramadol has greater affinity for μ-opioid receptor and provides additional prevention of 5- hydroxy tryptamine reuptake, while the (-)-tramadol is a successful noradrenaline reuptake inhibitor and intensifies its release by activating the auto receptor. Tramadol is prescribed to relieve moderate to severe pain management in patients. Tramadol does not show much serious adverse effects without any dependency potential in therapeutic doses as seen in other opioids, like morphine. Tramadol metabolite M1 also has μ-opioid receptor agonist activity, but it faces poor blood brain barrier permeability. In this review, we report the complete updated status of Tramadol along with its chemistry, synthesis, pharmacology, medicinal uses, adverse effects and its combinations available in the market. We have also covered Tramadol patents so that a complete overview provides a broader perspective for future designing of its derivatives and increase their potential use for pain management in terminal cancer patients.

Tramadol dispensing patterns and trends in Canada, 2007-2016

PURPOSE

Opioid use and associated mortality and morbidity have substantially increased in Canada, which recent interventions have aimed to reduce. Tramadol is an atypical prescription-only (but unscheduled under Canada's narcotics law) opioid analgesic and not subject to controls for other (eg, strong) opioids. Given experiences in different jurisdictions, tramadol may have been increasingly dispensed as a "substitute" drug during a period with increasingly restrictive controls for other (scheduled) opioids.

METHODS

We examined the annual population-level retail dispensing (as a proxy for use) of tramadol and (scheduled) "strong opioids" in Canadian provinces for 2007-2016 based on data from a representative national sample of community pharmacies, covering the majority of episodes of opioid dispensing. Data for both aforementioned formulation categories were converted into defined daily doses (DDD)/1000 population/day and examined descriptively and by segmented regression analyses (to identify significant breakpoints in trends).

RESULTS

Tramadol use strongly increased in all provinces until 2009. After 2009, tramadol dispensing levels either decelerated their increase or plateaued; "strong opioid" dispensing levels, in comparison, increased strongly until 2011 and decelerated or decreased for the remaining period. Tramadol was consistently dispensed at lower levels than "strong opioids."

CONCLUSIONS

Tramadol and "strong opioids" showed similar (bifurcated) use trends, with initial increases and subsequent inflections, yet reductions in dispensing occurred earlier for tramadol than for "strong opioids" (the latter occurring following with recent interventions). Distinct from experiences with differential opioid control regimes elsewhere, there is no evidence that tramadol figured as a "substitution" drug for increasingly restricted "strong opioids" in Canada.

Tramadol: a valuable treatment for pain in Southeast Asian countries

Background

The supply of controlled drugs is limited in the Far East, despite the prevalence of health disorders that warrant their prescription. Reasons for this include strict regulatory frameworks, limited financial resources, lack of appropriate training amongst the medical profession and fear of addiction in both general practitioners and the wider population. Consequently, the weak opioid tramadol has become the analgesic most frequently used in the region to treat moderate to severe pain.

Methods

To obtain a clearer picture of the current role and clinical use of tramadol in Southeast Asia, pain specialists from 7 countries in the region were invited to participate in a survey, using a questionnaire to gather information about their individual use and experience of this analgesic.

Results

Fifteen completed questionnaires were returned and the responses analyzed. Tramadol is used to manage acute and chronic pain caused by a wide range of conditions. Almost all the specialists treat moderate cancer pain with tramadol, and every one considers it to be significant or highly significant in the treatment of moderate to severe non-cancer pain. The reasons for choosing tramadol include efficacy, safety and tolerability, ready availability, reasonable cost, multiple formulations and patient compliance. Its safety profile makes tramadol particularly appropriate for use in elderly patients, outpatients, and for long-term treatment. The respondents strongly agreed that tighter regulation of tramadol would reduce its medical availability and adversely affect the quality of pain management. In some countries, there would no longer be any appropriate medication for cancer pain or the long-term treatment of chronic pain.

Conclusions

In Southeast Asia, tramadol plays an important part in the pharmacological management of moderate to severe pain, and may be the only available treatment option. If it were to become a controlled substance, the standard of pain management in the region would decline.

Pharmacotherapy of premature ejaculation: a systematic review and network meta-analysis

PURPOSE

The purpose of the study was to conduct a systematic evaluation of the different general prescribed drugs for premature ejaculation (PE).

METHODS

A systematic literature search of MEDLINE, Cochrane Central Register of Controlled Trials, and Web of Science for Systematic Reviews was performed on 1 March 2018. Intravaginal ejaculation latency time (IELT) was the main outcome. Analysis was performed under multivariate random-effects network model and efficacies of drugs were ranked with surface under the cumulative ranking (SUCRA) probabilities.

RESULTS

A total of 48 studies were reviewed and 40 of them were further enrolled into network meta-analysis. The majority of RCTs were of unclear methodological quality. Pooled evidence suggested that topical anaesthetic creams (TAs), tramadol, selective serotonin reuptake inhibitors (SSRIs), and phosphodiesterase type 5 inhibitors (PDE5is) are more effective at prolonging IELT comparing with placebo. TAs (90%) on demand (OD) and PDE5is plus SSRI (89.8%) had the highest SUCRA, which meant the most probable to be the most effective intervention.

CONCLUSIONS

We recommend the initial use of dapoxetine 30 mg OD for PE because it has been tested in largest and better designed clinical trials rather than it is more effective than the other drugs studied. TAs and tramadol 50 mg OD can be used as a viable alternative to oral treatment with SSRIs. PDE5is combined with SSRIs are more effective than SSRIs monotherapy but are also associated with more side effects. PDE5is OD can be recommended to PE patients with ED.

Acute tramadol enhances brain activity associated with reward anticipation in the nucleus accumbens

BACKGROUND

Tramadol is an analgesic with monoamine reuptake inhibition and μ-opioid receptor activation. Although tramadol has been widely used for treatment of various pain conditions, there is controversy over the risk of abuse potential. We examined the effects of tramadol on the reward system in humans using functional magnetic resonance imaging (fMRI) to assess the potential of tramadol for drug abuse or dependence.

METHODS

A randomized, double-blind, placebo-controlled, crossover study was conducted for 19 healthy adults under tramadol or placebo. In association with subjective mood questionnaires, monetary incentive delay (MID) task was performed to assess the neural response to reward anticipation during fMRI. Subjective mood measures and blood oxygenation level-dependent (BOLD) signal during gain and loss anticipation were compared between tramadol and placebo.

RESULTS

Tramadol significantly reduced anxiety (Z = - 2.513, p = 0.012) and enhanced vigor (Z = - 2.725, p = 0.006) compared with placebo. By Mood Rating Scale, tramadol provoked contented (Z = - 2.316, p = 0.021), relaxed (Z = - 2.236, p = 0.025), and amicable feelings (Z = - 2.015, p = 0.044) as well as increased alertness (Z = - 1.972, p = 0.049) and contentedness domains (Z = - 2.174, p = 0.030) compared with placebo. Several brain regions including nucleus accumbens (NAc) were activated during gain anticipation in the MID task under both tramadol and placebo. Tramadol increased the %BOLD signal change in NAc at +¥500 cue significantly more than the placebo (Z = - 2.295, p = 0.022).

CONCLUSION

Tramadol enhances the reward system and thereby may have abuse potential or precipitate drug abuse in human.

Cross state-dependency of learning between tramadol and MK-801 in the mouse dorsal hippocampus: involvement of nitric oxide (NO) signaling pathway

RATIONALE

Tramadol, an atypical μ-opioid receptor agonist, as a psychoactive drug, is frequently abused by human beings. Understanding the neurobiological mechanisms of drug-associated learning and memory formation may help prevent drug addiction and relapse. Previous study revealed that dorsal hippocampus (CA1) plays a crucial role in the retrieval of tramadol-associated memory and that its role depends on the expression of CA1 N-methyl-D-aspartate (NMDA) receptors (Jafari-Sabet et al. Can J Physiol Pharmacol 96:45-50, 2018).

OBJECTIVE

To clarify the exact mechanisms involved, the activation of CA1 nitric oxide (NO) signaling pathway by L-arginine (a nitric oxide precursor) on the interaction between tramadol and MK-801 in memory retrieval was examined. The dorsal hippocampal CA1 regions of adult male NMRI mice were bilaterally cannulated and a single-trial step-down inhibitory avoidance apparatus was used for the assessment of memory retrieval.

RESULTS

Post-training and/or pre-test microinjection of tramadol (0.5 and 1 μg/mouse) and/or a non-competitive NMDA receptor antagonist, MK-801 (0.25 and 0.5 μg/mouse), induced amnesia which were reversed when the same doses of the drugs were administered 24 h later in a pre-test session, suggesting tramadol state-dependent learning (SDL) and MK-801 SDL. The amnesia induced by post-training microinjection of tramadol (1 μg/mouse) was reversed by pre-test microinjection of MK-801 (0.25 and 0.5 μg/mouse). Pre-test microinjection of MK-801 (0.125 and 0.25 μg/mouse) with an ineffective dose of tramadol (0.25 μg/mouse) potentiated tramadol SDL. The amnesia induced by post-training microinjection of MK-801 (0.5 μg/mouse) was reversed by pre-test microinjection of tramadol (0.5 and 1 μg/mouse). Pre-test microinjection of tramadol (0.25 and 0.5 μg/mouse) with an ineffective dose of MK-801 (0.125 μg/mouse) potentiated MK-801 SDL. Pre-test microinjection of ineffective doses of L-arginine (0.125, 025, and 0.5 μg/mouse) improved amnesia induced by the co-administration of tramadol and MK-801. Pre-test microinjection of L-arginine (0.125, 025, and 0.5 μg/mouse) could not reverse amnesia induced by post-training microinjection of tramadol while same doses of L-arginine improved MK-801 response on tramadol SDL.

CONCLUSION

The results strongly propose that activation of CA1 NO signaling pathway has a pivotal role in cross SDL among tramadol and MK-801.

Improving the Clinical Pharmacologic Assessment of Abuse Potential: Part 1: Regulatory Context and Risk Management

PURPOSE

This article brings to the attention of drug developers the Food and Drug Administration's (FDA's) recent final Guidance to Industry on Assessment of Abuse Potential and provides practical suggestions about compliance with the Guidance.

PROCEDURES

The Guidance areas are reviewed, analyzed, and placed in the context of current scientific knowledge and best practices to mitigate regulatory risk.

FINDINGS

The Guidance provides substantial new detail on what needs to be done at all stages of drug development for central nervous system-active drugs. However, because many psychopharmacologic agents have unique preclinical and clinical features, the plan for each agent needs to be not only carefully prepared but also reviewed and approved by the FDA. Examples are provided where assumptions about interpretation of the Guidance can delay development.

CONCLUSIONS

If the expertise and experience needed for assessing abuse potential during drug development do not exist within a company, external preclinical and clinical expert should be involved. Consultation with the FDA is encouraged and important because the specific requirements for each drug will vary.

Evaluation of the Ecstasy influence on tramadol and its main metabolite plasma concentration in rats

BACKGROUND

Tramadol is prone to be abused alone, or in combination with 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy). It was reported that 95% of people with a history of substance abuse in the United States used tramadol in 2004. According to the WHO report in 2016, there was a growing number of tramadol abusers alone or in combination with psychoactive substances such as MDMA in particular in some Middle East countries. Higher concentrations of tramadol in plasma may lead to adverse drug reactions or lethal intoxication. In this study, the effect of MDMA on the pharmacokinetics of tramadol was examined in male rats.

METHODS

The effect of MDMA on Tmax, Cmax, area under the curve, elimination rate, and half-life of tramadol and its metabolites was examined. Two control and two treatment groups were designed. The treatment groups received MDMA 18 h before the administration of tramadol. Jugular vein blood samples were analyzed by high-performance liquid chromatography with fluorescent detector to determine the concentrations of tramadol and its metabolites. Independent-sample t-test was used to define the differences between pharmacokinetic parameters of control and treatment groups.

RESULTS

When tramadol administered intraperitoneally, the absorption rate of this drug was reduced, and a lower Cmax (40%) with longer Tmax (eight-fold) was achieved. MDMA exerted greater inhibitory effects on cytochrome P450 3A4 (CYP3A4) than on cytochrome P450 2D6 (CYP2D6). The M2 metabolite ratio was reduced by half, and because of the inhibition of M2 production, the M1 plasma concentration slightly increased.

CONCLUSIONS

According to the obtained data, MDMA treatment affected the absorption, distribution and metabolism phases of tramadol. This treatment increased the concentration of tramadol if administered intravenously and can latent the absorption of tramadol in oral route. However, MDMA was introduced as CYP2D6 inhibitor; in this study, MDMA inhibited CYP3A4 isoenzymes as well. This finding is important for the compounds that are metabolized through CYP3A4. It can be proposed that in abusers of MDMA who only receive tramadol for medical or nonmedical purposes in short intervals, the dangers of the intravenous administration of tramadol should be considered, and if tramadol is administered orally, the desired effect may not be achieved at the routine dose.

The role of tramadol in pain management in Latin America: a report by the Change Pain Latin America Advisory Panel

OBJECTIVE

Change Pain Latin America (CPLA) was created to enhance chronic pain understanding and develop pain management improving strategies in this region. During its seventh meeting (August 2016), the main objective was to discuss tramadol's role in treating pain in Latin America. Furthermore, potential pain management consequences were considered, if tramadol was to become more stringently controlled.

METHODS

Key topics discussed were: main indications for prescribing tramadol, its pharmacological characteristics, safety and tolerability, effects of restrictions on its availability and use, and consequent impact on pain care quality.

RESULTS

The experts agreed that tramadol is used to treat a wide spectrum of non-oncological pain conditions (e.g. post-surgical, musculoskeletal, post-traumatic, neuropathic, fibromyalgia), as well as cancer pain. Its relevance when treating special patient groups (e.g. the elderly) is recognized. The main reasons for tramadol's high significance as a treatment option are: its broad efficacy, an inconspicuous safety profile and its availability, considering that access to strong analgesics - mainly controlled drugs (classical opioids) - is highly restricted in some countries. The CPLA also agreed that tramadol is well tolerated, without the safety issues associated with long-term nonsteroidal anti-inflammatory drug (NSAID) use, with fewer opioid-like side effects than classical opioids and lower abuse risk.

CONCLUSIONS

In Latin America, tramadol is a valuable and frequently used medication for treating moderate to severe pain. More stringent regulations would have significant impact on its availability, especially for outpatients. This could cause regression to older and frequently inadequate pain management methods, resulting in unnecessary suffering for many Latin American patients.

Ketorolac, Oxymorphone, Tapentadol, and Tramadol: A Comprehensive Review

Pain remains a tremendous burden on patients and for the health care system, with uncontrolled pain being the leading cause of disability in this country. There are a variety of medications that can be used in the treatment of pain, including ketorolac, oxymorphone, tapentadol, and tramadol. Depending on the clinical situation, these drugs can be used as monotherapy or in conjunction with other types of medications in a multimodal approach. A strong appreciation of pharmacologic properties of these agents and potential side effects is warranted for clinicians.

Treatment of Neurogenic Cough with Tramadol: A Pilot Study

This study employs validated cough assessment tools to prospectively determine the impact of tramadol on cough severity and quality of life in subjects with neurogenic cough. The study was a prospective case series with planned data collection at a tertiary care academic medical center laryngology practice. Sixteen consecutive collected subjects with neurogenic cough prospectively completed pre- and posttreatment validated cough assessment tools, the cough severity index (CSI) and Leicester Cough Questionnaire (LCQ). All subjects in the study reported at least some improvement in their cough symptoms. In a Wilcoxon signed rank test that compared paired results, CSI scores improved from 23 to 14 and LCQ scores improved from 74 to 103 ( P = .003 and P = .005, respectively). This small preliminary assessment suggests that tramadol warrants additional evaluation as a treatment for neurogenic cough.

Preclinical assessment of the abuse potential of the orexin receptor antagonist, suvorexant

Suvorexant (Belsomra^®) is a dual orexin receptor antagonist approved for the treatment of insomnia. Because of its pharmacology within the central nervous system, intended therapeutic indication, and first-in-class status, an assessment of suvorexant abuse liability potential was required prior to marketing approval. The nonclinical abuse liability potential studies for suvorexant included: 1) rat drug-dependence model to assess physical dependence following abrupt cessation; 2) rat drug-discrimination model to examine the potential similarity of the interoceptive or subjective effects of suvorexant to those elicited by zolpidem and morphine; 3) self-administration model to assess the relative reinforcing efficacy of suvorexant in rhesus monkeys conditioned to self-administer methohexital. No significant signs of spontaneous drug withdrawal or 'discontinuation syndrome' were observed in rats following abrupt discontinuation of suvorexant. Suvorexant did not elicit complete cross-generalization to either a zolpidem or morphine training/reference stimuli in rats, and suvorexant was devoid of behavioral evidence of positive reinforcing efficacy in monkeys. These nonclinical findings suggested that suvorexant will have low abuse potential in humans. In the final regulatory risk assessment, suvorexant was placed into Schedule IV, likely due to its first-in-class status, its sedative properties, and the outcome of the clinical abuse potential assessment.

The Abuse Potential of Prescription Opioids in Humans-Closing in on the First Century of Research

While opioids are very effective analgesics for treating acute pain, humans have struggled with opiate addiction for millenia. An opium abuse epidemic in the early 1900's led the US government to develop a systematic research infrastructure and scientific plan to produce new compounds with analgesic properties but without abuse liability. This review describes the techniques that were developed for testing in the human laboratory, including empirically derived outcome measures and required elements for human abuse potential assessment. The evaluation and characterization of semi-synthetic and synthetic opioids, including full mu opioid agonists, partial agonists and mixed agonist-antagonists, are described across several decades of research. Finally, the prescription opioid epidemic beginning in the 1990's in the US led to a resurgence in abuse potential evaluations, and the application of these methods to the study of novel abuse-deterrent formulations is discussed.

Cortical excitability in tramadol dependent patients: A transcranial magnetic stimulation study

BACKGROUND

Addiction to tramadol, a widely used analgesic, is becoming increasingly common. Tramadol can also induce seizures even after a single clinical dose. We tested whether the epileptogenicity of tramadol was associated with any changes in cortical excitability and inhibitory transmission using transcranial magnetic stimulation (TMS).

METHODS

The study included 16 tramadol dependent patients and 15 age and sex matched healthy volunteers. Clinical evaluation was conducted using an addiction severity index. TMS assessment of excitability was conducted on the motor cortex since the response to each TMS pulse at that site is easily measured in terms of the amplitude of the twitches it evokes in contralateral muscles. Measures included resting and active motor threshold (RMT and AMT respectively), motor evoked potential (MEP) amplitude, cortical silent period (CSP) duration, transcallosal inhibition (TCI), and short interval intracortical inhibition and facilitation (SICI and ICF respectively). Urinary level of tramadol was measured immediately before assessing cortical excitability in each patient.

RESULTS

RMT and AMT were significantly lower, the duration of the CSP was shorter and SICI was reduced in patients compared with the control group. These findings are suggestive of increased neural excitability and reduced GABAergic inhibition following exposure to tramadol. Also there were negative correlations between the severity of tramadol dependence and a number of cortical excitability parameters (AMT, RMT, and CSP with P=0.002, 0.005, and 0.04 respectively).

CONCLUSIONS

The results provide evidence for hyperexcitability of the motor cortex coupled with inhibitory deficits in tramadol dependent patients.

Worldwide research productivity on tramadol: a bibliometric analysis

BACKGROUND

Pain management and safe use of analgesics is an important medical issue. Tramadol is an old analgesic with controversial properties. Evaluation of worldwide scientific output on tramadol has not been explored. Therefore, the main objective of this study was to give a bibliometric overview of global research productivity on tramadol.

METHODS

SciVerse Scopus was used to retrieve and quantitatively and qualitatively analyze worldwide publications on tramadol.

RESULTS

A total of 2059 original and review research articles on tramadol were retrieved from Scopus. Forty-six documents (2.23 %) were published in Anesthesia and Analgesia Journal whereas 30 (1.46 %) were published in Arzneimittel Forschung Drug Research Journal. Retrieved tramadol documents were published from 71 countries and appeared in 160 peer reviewed journals. Although the United States of America (259; 12.86 %) had the largest contribution to tramadol publications; the contribution by other countries like Turkey (232; 11.27) India (189; 8.09 %) and Germany (176; 8.56 % was not far away from that of USA. The most productive institution was Grunenthal, Germany (47; 2.28 %) followed by Tehran University of Medical Sciences, Iran (29; 1.41 %), and, Ortho-McNeil Pharmaceutical Incorporated, USA (25; 1.21 %). Of the 2059 documents, there were 370 documents about dependence. The leading institution in documents pertaining to tramadol dependence was Grunenthal GmbH (18; 4.86 %) followed by Ortho-McNeil Pharmaceutical Incorporated (17; 4.59 %).

CONCLUSIONS

The current study showed that there is an obvious interest in tramadol research. More efforts are needed to clarify the abuse potential and safety profile of tramadol to help in determining the legal status of tramadol. Collaboration among pharmaceutical industry, clinical researchers and academic institutions can improve research quantity and quality on tramadol.

A randomized, double-blind, placebo-controlled, crossover trial of "on-demand" tramadol for treatment of premature ejaculation

Objectives:

The objective of this study is to assess the dose-related effects of tramadol on a group of patients with premature ejaculation (PE).

Subjects and Methods:

During the period of months between June 2010 and July 2012, 180 PE patients presented to outpatient clinic of our hospital. Patients were randomized in a 1:1:1 fashion to receive different sequences of the three medications: placebo, 50 mg of tramadol and 100 mg of tramadol. Every patient received 10 doses of each medication for 2 months. Intra-vaginal ejaculatory latency time (IELT) was recorded in seconds initially and for each arm. Successful treatment of PE is defined if IELT exceeded 120 s. Side-effects of medications were reported.

Results:

Of patients enrolled, 125 (69.4%) continued the study. Patients’ age range was 20-55 years with PE complaint of 1 to 10 years duration. Mean IELT was 72 at presentation, 82 for placebo, 150 for tramadol 50 mg, and 272 for tramadol 100 mg (P < 0.001 for all comparisons). PE was successfully treated in only 2.4% of patients with placebo, in contrast to 53.6% and 85.6% with 50 and 100 mg tramadol, respectively (P < 0.001 for all comparisons). On multivariate logistic regression analysis, baseline IELT was the only predictor of successful treatment of PE with both tramadol 50 mg (odds ratio [OR]: 1.05, 95% confidence interval [CI]: 1.03-1.07, P < 0.001) and tramadol 100 mg (OR: 1.07, 95% CI: 1.04-1.11, P < 0.001). Postmicturition dribble annoyed 12.8% of those who received 50 mg tramadol and 33.6% of those who received 100 mg tramadol (P < 0.001). Weak scanty ejaculation was the main complaint in 7.2% versus 21.6% of those using 50 and 100 mg tramadol, respectively (P = 0.002). Two patients discontinued tramadol 100 mg due to side-effects.

Conclusion:

Tramadol hydrochloride exhibits a significant dose-related efficacy and side-effects over placebo for treatment of PE.