Serotonin syndrome following the administration of tramadol with paroxetine

A systematic review and meta-analysis of randomized controlled trials of "on-demand" use of tramadol vs "on-demand" use of paroxetine in the management of patients with premature ejaculation

AIM

To evaluate the effect of "on-demand" use of tramadol vs "on-demand" use of paroxetine in the management of patients with premature ejaculation (PE).

MATERIALS AND METHODS

A systematic search of PubMed, EMBASE, Cochrane Library databases and original references of the included articles was performed. PRISMA checklist was followed. The Cochrane Handbook was used to evaluate the quality of the included research.

RESULTS

A total of seven articles including 663 patients were studied. The results indicated that patients who received on-demand therapy of tramadol or paroxetine showed significant improvement compared with those treated with placebo, as assessed by intravaginal ejaculatory latency time (IELT) (P < .00001 and P = .02, respectively) and sexual satisfaction score (P < .00001 and P < .00001, respectively). Furthermore, Patients who were treated with on-demand tramadol had a better effect than those treated with on-demand paroxetine in respect of IELT (P = .01) and sexual satisfaction score (P = .03). With regard to safety, the most common adverse event for the tramadol group was sleep disturbance and the most common adverse event for the paroxetine group was a headache. No serious adverse event was observed in both groups.

CONCLUSIONS

Compared with placebo, on-demand therapy of tramadol or paroxetine showed a better improvements in IELT and sexual satisfaction scores. Besides, on-demand tramadol revealed a better effect than on-demand paroxetine for patients with PE, and patients in both groups showed good tolerance.

Characterizing tramadol users with potentially inappropriate co-medications: A latent class analysis among older adults

Background

Although tramadol is an effective weak opioid analgesic, careful monitoring of potential central nervous system adverse reactions in older adults is needed, especially when used with concomitant medications which may trigger the adverse effects. We aimed to characterize tramadol users with potentially inappropriate co-medications in older adults using a latent class analysis (LCA).

Method

Patients aged 65 years or older using tramadol and receiving potentially inappropriate co-medications were included from a nationwide healthcare claims database. We defined antidepressants, first-generation antihistamines, and anxiolytics as potentially inappropriate co-medications. We applied an LCA for grouping tramadol users based on the common characteristics of medication use and healthcare utilization, and each patient was probabilistically assigned to a class. Patients’ characteristics in different latent classes were compared. Potential adverse drug reactions (ADRs) was defined as the any visits for emergency department after the occurrence of potentially inappropriate co-medications. Logistic regression analysis was used to examine the association between latent classes and potential ADRs.

Results

We identified four distinct latent classes of tramadol users representing different patterns of co-medications: multiple potential drug-drug interaction (pDDI) combination users, antihistamines-tramadol users, antidepressants-tramadol users, and anxiolytics-tramadol users. Multiple pDDI combination users showed high proportion of regular tramadol use, tended to visit more medical institutions, and had a high Charlson comorbidity score. The duration of use of potentially inappropriate co-medications with tramadol was the longest in multiple pDDI combination users and the shortest in antihistamines-tramadol users.

When compared with antihistamines-tramadol users, increased potential ADR risk was observed in multiple pDDI combination users (adjusted odds ratio (OR), 1.81; 95% confidence interval (CI), 1.75–1.88), antidepressants-tramadol users (1.24; 1.19–1.29), and anxiolytics-tramadol users (1.04; 1.00–1.08).

Conclusions

Four distinct classes were identified among older adults using tramadol and potentially inappropriate co-medications. Differences in potential ADR risk were observed between these classes. These findings may help to identify patients at a high risk for ADRs owing to potentially inappropriate co-medications with tramadol.

Opioids, Polypharmacy, and Drug Interactions: A Technological Paradigm Shift Is Needed to Ameliorate the Ongoing Opioid Epidemic

Polypharmacy is a common phenomenon among adults using opioids, which may influence the frequency, severity, and complexity of drug–drug interactions (DDIs) experienced. Clinicians must be able to easily identify and resolve DDIs since opioid-related DDIs are common and can be life-threatening. Given that clinicians often rely on technological aids—such as clinical decision support systems (CDSS) and drug interaction software—to identify and resolve DDIs in patients with complex drug regimens, this narrative review provides an appraisal of the performance of existing technologies. Opioid-specific CDSS have several system- and content-related limitations that need to be overcome. Specifically, we found that these CDSS often analyze DDIs in a pairwise manner, do not account for relevant pharmacogenomic results, and do not integrate well with electronic health records. In the context of polypharmacy, existing systems may encourage inadvertent serious alert dismissal due to the generation of multiple incoherent alerts. Future technological systems should minimize alert fatigue, limit manual input, allow for simultaneous multidrug interaction assessments, incorporate pharmacogenomic data, conduct iterative risk simulations, and integrate seamlessly with normal workflow.

Severe Uncontrolled Pain in Buttock in a Patient on Naltrexone: A Diagnostic Challenge

A 26-year-old woman with a history of intravenous drug use was admitted to hospital with worsening pain in the right buttock radiating to the lateral part of the thigh and to the calf with no suspicion of cauda equina compression. Eventually, a diagnosis of sacroiliitis was made and appropriate antibiotics were administered. Provision of analgesia for this patient was difficult. On admission her medications included naltrexone, venlafaxine and tramadol. Initially naltrexone was continued and analgesia provided by epidural local anaesthetic and clonidine, intravenous ketamine and oral agents. After several days, naltrexone was ceased and opioids were used in addition to the other analgesics. The epidural analgesia was only partially effective, perhaps because of inadequate blockade of the L4-S1 nerve roots, which carry sensation from the sacroiliac joint.

Naltrexone is a long-acting opioid antagonist. If opioid analgesia is planned, it is necessary to cease naltrexone for 24 to 72 hours. In an emergency, if non-opioid techniques prove ineffective, short-acting opioids can be titrated to effect in a monitored environment.

Interaction between tramadol and selective serotonin reuptake inhibitors: are doctors aware of potential risks in their prescription practice?

Objectives

The combination of a selective serotonin reuptake inhibitor (SSRI) or serotonin-norepinephrine reuptake inhibitor (SNRI) with tramadol can result in serotonin syndrome, characterised by neuromuscular and autonomic nervous system excitation and altered mental state. The incidence of serotonin syndrome with this combination of drugs is low, and the serotonin syndrome is generally mild or moderate in form, but can be life threatening and is more easily prevented than treated. We aimed to investigate whether prescribers in a general hospital were aware of this risk and if it influenced their prescriptions.

Methods

A questionnaire was sent to 194 physicians in a general teaching hospital with over 650 beds in The Netherlands. The questionnaire presented four cases, two of whom used an SSRI or SNRI among other medications, and asked the respondents to prescribe an opioid in each case. The respondents were not aware of the focus of our research. Actual prescription rates of tramadol in admitted patients who did or did not use an SSRI or SNRI were assessed using the hospital pharmacy database.

Results

Based on the questionnaire, respondents prescribed tramadol equally in patients with or without concomitant use of SSRIs/SNRIs. About one-third of respondents who prescribed tramadol indicated they were aware of the potential interaction with SSRIs/SNRIs. About one-fifth deliberately avoided tramadol because a potential interaction with SSRIs/SNRIs was identified. However, there was no difference in actual tramadol prescriptions, as recorded in the hospital pharmacy database: 23.8% of SSRI/SNRI users received tramadol versus 24.6% of non-SSRI/SNRI-users (calculated OR 0.96; 95% CI 0.78 to 1.17).

Conclusions

In total, 20-30% of prescribers in a general hospital were aware of the potential interaction between tramadol and SSRIs or SNRIs, yet this did not translate to a difference in tramadol prescriptions between SSRI/SNRI users and non-users, as documented in the hospital pharmacy database. A physician's decision to prescribe tramadol to SSRI/SNRI users may be guided by a comprehensive individual benefit-risk assessment; expected benefits of tramadol may outweigh the small risk of serotonin syndrome. In order to increase awareness of the potential risk of a serotonin syndrome, hospital pharmacies may play an important role in signalling the potential interaction and providing information on the benefits and risks of tramadol and alternative analgesics in the presence of SSRIs or SNRIs.

Tramadol overdose causes seizures and respiratory depression but serotonin toxicity appears unlikely

CONTEXT

Tramadol is a commonly used centrally acting analgesic associated with seizures and suspected to cause serotonin toxicity in overdose.

OBJECTIVE

This study sought to investigate the effects of tramadol overdose, and included evaluation for serotonin toxicity based on the Hunter Serotonin Toxicity Criteria where the seven clinical features of spontaneous clonus, inducible clonus, ocular clonus, agitation, diaphoresis, tremor and hyperreflexia are examined for in all patients taking serotonergic medications; seizures and central nervous system depression.

MATERIALS AND METHODS

This was an observational cases series based on a retrospective review of tramadol overdoses (> 400 mg) admitted to a tertiary toxicology unit from November 2000 to June 2013. Demographic details, information on ingestion (dose and co-ingestants), clinical effects, complications (seizures, serotonin toxicity and cardiovascular effects) and intensive care unit (ICU) admission were extracted from a clinical database.

RESULTS

There were 71 cases of tramadol overdose (median age: 41 years, range: 17-69 years; and median ingested dose: 1000 mg, interquartile range [IQR]: 800-2000 mg). Seizures were dose related and occurred in 8 patients, one of them co-ingested a benzodiazepine compared with 16 patients without seizures. There were no cases of serotonin toxicity meeting the Hunter Serotonin Toxicity Criteria. Tachycardia occurred in 27 and mild hypertension occurred in 32. The Glasgow Coma Score was < 15 in 29 and < 9 in 5 patients; three co-ingested tricyclic antidepressants and two tramadol alone (3000 mg and 900 mg). Respiratory depression occurred in 13, median dose: 2500 (IQR: 1600-3000) mg which was significantly different (p = 0.003) to patients without respiratory depression, median dose: 1000 (IQR: 750-1475) mg. Eight patients were admitted to ICU, five due to co-ingestant toxicity and three for respiratory depression.

DISCUSSION

Tramadol overdose was associated with a significant risk of seizures and respiratory depression in more severe cases, both which appear to be related to the ingested dose. There were no cases of serotonin toxicity, while opioid-like effects and adrenergic effects were prominent.

CONCLUSION

Tramadol overdose is associated with seizures and respiratory depression, but is unlikely to cause serotonin toxicity.

Serotonin toxicity

Serotonin toxicity is a potentially life-threatening condition associated with a range of psychotropic medications, co-administration of specific combinations of agents and overdose of certain drugs. It is associated with a wide diversity of clinical signs and symptoms, including cognitive, autonomic and somatic effects, as well as serious complications, including possible death. Diagnosis is often challenging and requires a high index of suspicion. Differential diagnosis includes syndromes such as neuroleptic malignant syndrome. Management depends on the causal agent and urgency of clinical presentation. Treatment may involve discontinuing the causal agent and providing supportive measures, or emergency intervention to preserve vital functions (airway, breathing, circulation), amongst other measures. Further research is needed to clarify the incidence of serotonin toxicity, issues related to differential diagnosis, optimal management of the condition, and treatment of mood problems following serotonin toxicity.

Mutations in monoamine oxidase (MAO) genes in mice lead to hypersensitivity to serotonin-enhancing drugs: implications for drug side effects in humans

A possible side effect of serotonin-enhancing drugs is the serotonin syndrome, which can be lethal. Here we examined possible hypersensitivity to two such drugs, the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP) and the atypical opioid tramadol, in mice lacking the genes for both monoamine oxidase A (MAOA) and MAOB. MAOA/B-knockout (KO) mice displayed baseline serotonin syndrome behaviors, and these behavioral responses were highly exaggerated following 5-HTP or tramadol versus baseline and wild-type (WT) littermates. Compared with MAOA/B-WT mice, baseline tissue serotonin levels were increased ∼2.6-3.9-fold in MAOA/B-KO mice. Following 5-HTP, serotonin levels were further increased ∼4.5-6.2-fold in MAOA/B-KO mice. These exaggerated responses are in line with the exaggerated responses following serotonin-enhancing drugs that we previously observed in mice lacking the serotonin transporter (SERT). These findings provide a second genetic mouse model suggestive of possible human vulnerability to the serotonin syndrome in individuals with lesser-expressing MAO or SERT polymorphisms that confer serotonergic system changes.

Serotonin syndrome: is it a reason to avoid the use of tramadol with antidepressants?

BACKGROUND

There is a warning associated with all serotonergic antidepressants and its concomitant use with tramadol due to the concern for a drug-drug interaction resulting in serotonin syndrome (SS). The prescribing of antidepressants with tramadol may be unnecessarily restricted due to fear of causing this syndrome.

OBJECTIVES

There are 3 objectives of this review. To (1) review case reports of SS associated with the combination of tramadol and antidepressant drugs in recommended doses, (2) describe the mechanisms of the drug interaction, and (3) identify the potential risk factors for SS.

METHODS

Case reports of SS associated with tramadol and antidepressants were identified via Cochrane Library, PubMed, and Ovid (through October 2012) using search terms SS, tramadol, antidepressants, fluoxetine, sertraline, paroxetine, fluvoxamine, citalopram, escitalopram, venlafaxine, desvenlafaxine, duloxetine, mirtazapine, milnacipran, trazodone, vilazodone, and bupropion. Cases involving monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants were excluded.

RESULTS

Nine articles were identified describing 10 cases of suspected SS associated with therapeutic doses of tramadol combined with an antidepressant. Mechanisms of the drug-drug interactions involve pharmacodynamic, pharmacokinetic, and possible pharmacogenetic factors.

CONCLUSIONS

Review of the available case reports of tramadol combined with antidepressant drugs in therapeutic doses indicates caution in regard to the potential for SS but does not constitute a contraindication to their use. Tramadol is only contraindicated in combination with MAOIs but not other antidepressants in common use today. These case reports do suggest several factors associated with a greater risk of SS, including increased age, higher dosages, and use of concomitant potent cytochrome P450 2D6 inhibitors. Tramadol can be safely combined with antidepressants; however, monitoring and counseling patients are prudent when starting a new serotonergic agent or when doses are increased.

On-demand use of tramadol, sildenafil, paroxetine and local anaesthetics for the management of premature ejaculation: A randomised placebo-controlled clinical trial

Objectives

To compare the clinical efficacy of the on-demand use of four drugs in the management of patients with premature ejaculation (PE), as the off-label use of selective serotonin-reuptake inhibitors and topical penile anaesthetics is frequently indicated for the management of patients with PE, and tramadol HCl and sildenafil citrate were also tried for managing this disorder, but with recommendations based on weak evidence.

Patients and methods

This was a single-centre, single-blind, placebo-controlled clinical trial conducted on 150 patients who had PE for >1 year. Patients were randomised equally into five groups. On-demand tramadol, sildenafil, paroxetine, local lidocaine gel or placebo was given for patients in groups 1–5, respectively. During the month before treatment, the intravaginal ejaculation latency time (IELT) and sexual satisfaction scores (on a 0–5-point scale) were measured and compared to the mean IELT and sexual satisfaction scores recorded during 4 weeks of on-demand drug administration, with monitoring of any possible side-effects.

Results

Tramadol-treated patients had a significantly longer mean (SD) IELT, of 351 (119) s, than the other groups. Local anaesthetic was significantly better than paroxetine in prolonging the IELT, at 278 (111) vs. 186 (65) s, respectively. The improvement in sexual satisfaction was significantly better in the sildenafil group, with a mean (SD) improvement of 2.9 (1) points, than in the paroxetine and local anaesthetic groups, at 2.2 (0.9) and 1.9 (0.9) points, respectively.

Conclusions

The four drugs significantly improved IELT values over placebo. Tramadol was associated with significantly longer IELT values, whilst sildenafil induced significantly better sexual satisfaction than the other drugs. The four drugs had tolerable side-effects.

Effects of imidazoline I₂ receptor ligands on morphine- and tramadol-induced antinociception in rats

Currently available analgesics cannot meet the increasing clinical needs and new analgesics with better therapeutic profiles are in great demand. The imidazoline I₂ receptor is an emerging drug target for analgesics. However, few studies have examined the effects of selective I₂ receptor ligands on the antinociceptive activity of opioids. This study examined the antinociceptive effects of the opioids morphine (0.1-10 mg/kg) and tramadol (3.2-56 mg/kg), the nonselective I₂ receptor ligand agmatine (10-100 mg/kg), and the selective I₂ receptor ligands 2-(2-benzofuranyl)-2-imidazoline hydrochloride (2-BFI; 1-10 mg/kg) and 2-(4, 5-dihydroimidazol-2-yl) quinoline hydrochloride (BU224; 1-10mg/kg), alone and in combination, in a warm water tail withdrawal procedure in rats. Morphine and tramadol but not agmatine, 2-BFI or BU224 increased tail withdrawal latency in a dose-related manner at 48°C water. Agmatine and 2-BFI but not BU224 dose-dependently enhanced the antinociceptive effects of morphine and tramadol, shifting the dose-effect curves of morphine and tramadol leftward. The enhancement of agmatine and 2-BFI on morphine and tramadol antinociception was prevented by BU224. These results, combined with the fact that BU224 and 2-BFI share similar behavioral effects under other conditions, suggest that BU224 has lower efficacy than 2-BFI at I₂ receptors, and that the enhancement of opioid antinociception by I₂ receptor ligands depends on their efficacies.

Advances in perioperative pain management: use of medications with dual analgesic mechanisms, tramadol & tapentadol

Recovery from ambulatory surgical procedures can be limited by postoperative pain. Inadequate analgesia may delay or prevent patient discharge and can result in readmission. More frequently, postoperative pain produces discomfort and interrupts sleep, contributing to postoperative fatigue. The development of effective analgesic regimens for the management of postoperative pain is a priority especially in patients with impaired cardiorespiratory, hepatic, or renal function. Tramadol and tapentadol hydrochloride are novel in that their analgesic actions occur at multiple sites. Both agents are reported to be mu-opioid receptor agonists and monoamine-reuptake inhibitors. In contrast to pure opioid agonists, both drugs are believed to have lower risks of respiratory depression, tolerance, and dependence. The Food and Drug Administration has approved both drugs for the treatment of moderate-to-severe acute pain in adults. This article provides an evidence-based account of the role of tramadol and tapentadol in modern clinical practice.

Tramadol and another atypical opioid meperidine have exaggerated serotonin syndrome behavioural effects, but decreased analgesic effects, in genetically deficient serotonin transporter (SERT) mice

The serotonin syndrome is a potential side-effect of serotonin-enhancing drugs, including antidepressants such as selective serotonin reuptake inhibitors (SSRIs) and monoamine oxidase inhibitors (MAOIs). We recently reported a genetic mouse model for the serotonin syndrome, as serotonin transporter (SERT)-deficient mice have exaggerated serotonin syndrome behavioural responses to the MAOI tranylcypromine and the serotonin precursor 5-hydroxy-l-tryptophan (5-HTP). As numerous case reports implicate the atypical opioids tramadol and meperidine in the development of the human serotonin syndrome, we examined tramadol and meperidine as possible causative drugs in the rodent model of the serotonin syndrome in SERT wild-type (+/+), heterozygous (+/-) and knockout (-/-) mice. Comparisons were made with SERT mice treated with either vehicle or morphine, an opioid not implicated in the serotonin syndrome in humans. Here we show that tramadol and meperidine, but not morphine, induce serotonin syndrome-like behaviours in mice, and we show that this response is exaggerated in mice lacking one or two copies of SERT. The exaggerated response to tramadol in SERT-/- mice was blocked by pretreatment with the 5-HT1A antagonist WAY 100635. Further, we show that morphine-, meperidine- and tramadol-induced analgesia is markedly decreased in SERT-/- mice. These studies suggest that caution seems warranted in prescribing or not warning patients receiving SSRIs or MAOIs that dangerous side-effects may occur during concurrent use of tramadol and similar agents. These findings suggest that it is conceivable that there might be increased vulnerability in individuals with SERT polymorphisms that may reduce SERT by more than 50%, the level in SERT+/- mice.

Adverse drug interactions involving common prescription and over-the-counter analgesic agents

BACKGROUND

Eight analgesic preparations with approved indications for acute pain were among the top 200 drugs prescribed in the United States in 2006. In addition, an estimated 36 million Americans use over-the-counter (OTC) analgesics daily. Given this volume of use, it is not surprising that a number of drug interactions involving analgesic drugs have been reported.

OBJECTIVES

This article examines the pharmacologic factors that enhance the clinical relevance of potential drug interactions and reviews the literature on drug interactions involving the most commonly used analgesic preparations in the United States.

METHODS

A PubMed search was conducted for English-language articles published between January 1967 and July 2007. Among the search terms were drug interactions, acetaminophen, aspirin, ibuprofen, naproxen, celecoxib, NSAIDs, hydrocodone, oxycodone, codeine, tramadol, OTC analgesics, alcohol, ethanol, antihypertensive drugs, methotrexate, warfarin, SSRIs, paroxetine, fluoxetine, sertraline, citalopram, serotonin syndrome, MAOIs, and overdose. Controlled clinical trials, case-control studies, and case reports were included in the review.

RESULTS

A number of case reports and well-controlled clinical trials were identified that provided evidence of the relatively well known drug-drug interactions between prescription/OTC NSAIDs and alcohol, antihypertensive drugs, high-dose methotrexate, and lithium, as well as between frequently prescribed narcotics and other central nervous system depressants. In contrast, the ability of recent alcohol ingestion to exacerbate the hepatotoxic potential of therapeutic doses of acetaminophen is not supported by either case reports or clinical research. Use of ibuprofen according to OTC guidelines in patients taking cardioprotective doses of aspirin does not appear to interfere with aspirin's antiplatelet activity, whereas chronic prescription use of ibuprofen and other NSAIDs may interfere. Low-dose aspirin intake appears to abolish the gastroprotective effects of cyclooxygenase-2-selective inhibitors, including celecoxib. There is evidence of other less well known and potentially clinically significant drug-drug interactions, including the ability of selective serotonin reuptake inhibitors to inhibit the analgesic activity of tramadol and codeine through inhibition of their metabolic activation, to induce serotonin syndrome when used chronically in the presence of high doses of tramadol through synergistic serotonergic action, and to increase the potential for gastrointestinal bleeding associated with NSAID therapy through additive or supra-additive antiplatelet activity.

CONCLUSIONS

Considering the widespread use of analgesic agents, the overall incidence of serious drug-drug interactions involving these agents has been relatively low. The most serious interactions usually involved other interacting drugs with low therapeutic indices or chronic and/or high-dose use of an analgesic and the interacting drug.

Tramadol HCL has promise in on-demand use to treat premature ejaculation

INTRODUCTION

Premature ejaculation (PE) is a worldwide problem without an approved treatment. Selective serotonin reuptake inhibitors (SSRIs) are widely used "off label" as pharmacotherapeutic agents in the treatment of PE.

AIM

This study investigates Tramadol efficacy for on-demand treatment of PE.

MAIN OUTCOMES MEASURES

Intravaginal ejaculation latency time (IELT) was used as an objective tool to assess the efficacy of the investigated treatments.

MATERIALS AND METHODS

Single-blind, placebo-controlled, crossover, stopwatch monitored two-period study was conducted, on 60 patients with lifelong PE. PE was defined as IELT of <2 minutes in 80% of intercourse episodes. A total of 25 mg of Tramadol hydrochloride was given to one group (30) prior to intercourse and placebo was supplied for the other group (30) for 8 weeks. Drugs were taken 1-2 hours before sexual activity and sexual intercourse was required at least once per week. After the initial treatment period, the two groups took the alternate medication for another 2 months. The two 8-week treatment periods were separated by 1 week washout period. IELT was timed by a stopwatch at each intercourse and was reported by patients or partners.

RESULTS

The baseline (mean +/- SD) IELT for patients before treatment was 1.17 +/- 0.39 minutes. At the end of the treatment period utilizing the active drug, the mean IELT was increased significantly in patients on Tramadol treatment to 7.37 +/- 2.53 minutes. The same patients on placebo medication had mean IELT of only 2.01 +/- 0.71 minutes. Patients uniformly reported satisfaction with their resulting control over ejaculation.

CONCLUSIONS

Tramadol, a drug with a proven safety record as an anti-inflammatory agent, shows promise as a drug for treating rapid ejaculation.

Clinical pharmacology of tramadol

Tramadol, a centrally acting analgesic structurally related to codeine and morphine, consists of two enantiomers, both of which contribute to analgesic activity via different mechanisms. (+)-Tramadol and the metabolite (+)-O-desmethyl-tramadol (M1) are agonists of the mu opioid receptor. (+)-Tramadol inhibits serotonin reuptake and (-)-tramadol inhibits norepinephrine reuptake, enhancing inhibitory effects on pain transmission in the spinal cord. The complementary and synergistic actions of the two enantiomers improve the analgesic efficacy and tolerability profile of the racemate. Tramadol is available as drops, capsules and sustained-release formulations for oral use, suppositories for rectal use and solution for intramuscular, intravenous and subcutaneous injection. After oral administration, tramadol is rapidly and almost completely absorbed. Sustained-release tablets release the active ingredient over a period of 12 hours, reach peak concentrations after 4.9 hours and have a bioavailability of 87-95% compared with capsules. Tramadol is rapidly distributed in the body; plasma protein binding is about 20%. Tramadol is mainly metabolised by O- and N-demethylation and by conjugation reactions forming glucuronides and sulfates. Tramadol and its metabolites are mainly excreted via the kidneys. The mean elimination half-life is about 6 hours. The O-demethylation of tramadol to M1, the main analgesic effective metabolite, is catalysed by cytochrome P450 (CYP) 2D6, whereas N-demethylation to M2 is catalysed by CYP2B6 and CYP3A4. The wide variability in the pharmacokinetic properties of tramadol can partly be ascribed to CYP polymorphism. O- and N-demethylation of tramadol as well as renal elimination are stereoselective. Pharmacokinetic-pharmacodynamic characterisation of tramadol is difficult because of differences between tramadol concentrations in plasma and at the site of action, and because of pharmacodynamic interactions between the two enantiomers of tramadol and its active metabolites. The analgesic potency of tramadol is about 10% of that of morphine following parenteral administration. Tramadol provides postoperative pain relief comparable with that of pethidine, and the analgesic efficacy of tramadol can further be improved by combination with a non-opioid analgesic. Tramadol may prove particularly useful in patients with a risk of poor cardiopulmonary function, after surgery of the thorax or upper abdomen and when non-opioid analgesics are contraindicated. Tramadol is an effective and well tolerated agent to reduce pain resulting from trauma, renal or biliary colic and labour, and also for the management of chronic pain of malignant or nonmalignant origin, particularly neuropathic pain. Tramadol appears to produce less constipation and dependence than equianalgesic doses of strong opioids.

Serotonin Syndrome Resulting from Coadministration of Tramadol, Venlafaxine, and Mirtazapine

OBJECTIVE

To report a case of serotonin syndrome (SS) resulting from the addition of tramadol to a medication regimen of venlafaxine and mirtazapine.

CASE SUMMARY

A 47-year-old white man receiving combined mirtazapine and venlafaxine therapy for major depressive disorder developed agitation, confusion, severe shivering, diaphoresis, myoclonus, hyperreflexia, mydriasis, tachycardia, and fever on coadministration of tramadol for chronic pain. An objective causality assessment revealed that the addition of tramadol was the probable cause of the adverse reaction.

DISCUSSION

SS is a potentially fatal iatrogenic complication of serotonergic polypharmacy. Considered idiopathic in presentation, it typically appears after initiation or dose escalation of the offending agent to a regimen including other serotonergic agents. All drugs that directly or indirectly increase central serotonin neurotransmission at postsynaptic 5-HT1A and 5-HT2A receptors can produce SS. Individual vulnerability appears to play a role in the development of SS. It is likely that the activation of 5-HT1A receptors by mirtazapine, the combined serotonin reuptake inhibition by venlafaxine and tramadol, as well as possible serotonin release by tramadol, contributed to the development of SS in this case.

CONCLUSION

It is vital that clinicians are aware of the potential for SS when psychotropic and nonpsychotropic agents are coadministered to certain patients, such as those with both depression and chronic pain.

Tramadol: a review of its use in perioperative pain

Tramadol is a synthetic, centrally acting analgesic agent with 2 distinct, synergistic mechanisms of action, acting as both a weak opioid agonist and an inhibitor of monoamine neurotransmitter reuptake. The 2 enantiomers of racemic tramadol function in a complementary manner to enhance the analgesic efficacy and improve the tolerability profile of tramadol. In several comparative, well designed studies, oral and parenteral tramadol effectively relieved moderate to severe postoperative pain associated with surgery. Its overall analgesic efficacy was similar to that of morphine or alfentanil and superior to that of pentazocine. Tramadol provided effective analgesia in children and in adults for both inpatient and day surgery. Tramadol was generally well tolerated in clinical trials. The most common adverse events (incidence of 1.6 to 6.1%) were nausea, dizziness, drowsiness, sweating, vomiting and dry mouth. Importantly, unlike other opioids, tramadol has no clinically relevant effects on respiratory or cardiovascular parameters at recommended doses in adults or children. Tramadol also has a low potential for abuse or dependence.

CONCLUSIONS

The efficacy of tramadol for the management of moderate to severe postoperative pain has been demonstrated in both inpatients and day surgery patients. Most importantly, unlike other opioids, tramadol has no clinically relevant effects on respiratory or cardiovascular parameters. Tramadol may prove particularly useful in patients with poor cardiopulmonary function, including the elderly, the obese and smokers, in patients with impaired hepatic or renal function, and in patients in whom nonsteroidal anti-inflammatory drugs are not recommended or need to be used with caution. Parenteral or oral tramadol has proved to be an effective and well tolerated analgesic agent in the perioperative setting.

A second trial of clozapine in a case of granulocytopenia

It is generally believed that agranulocytosis, a major problem with clozapine treatment, will tend to occur dose-dependently once it develops in an individual. Therefore, despite clinical progress obtained, the drug has to be discontinued and treatment shifts to another drug. We report on the case of a 29-year-old woman with DSM-IV undifferentiated schizophrenia who developed agranulocytosis after 5 years of 300 mg/day clozapine treatment. The drug was withdrawn and two trials with thioridazine and olanzapine were unsuccessful. Four months after clozapine suspension, we decided to make a further trial, reintroducing clozapine titrated up to 500 mg/day. The patient's symptoms improved and blood leukocytes remained within the normal range after eight months. Copyright 2000 John Wiley & Sons, Ltd.

Serotonin syndrome with fluoxetine plus tramadol

Images

St. John's wort and antidepressant drug interactions in the elderly

There is increasing interest in and use of the herbal preparation St. John's wort. Hypericin, the major active ingredient, has many psychoactive properties. The agent is sold in the US as a nutritional supplement and is recommended for numerous conditions, including depression, anxiety, insomnia, and inflammation. We report a series of five cases of clinically diagnosed central serotonergic syndrome among elderly patients who combined prescription antidepressants with St. John's wort. Older adults are large consumers of both over-the-counter and prescription medications. They are particularly vulnerable to interactions between medications and products sold as nutritional or herbal supplements. St. John's wort requires further evaluation due to potential for drug interactions with central nervous system agents and for more definitive therapeutic indications.