Ginsenoside Re Protects against Serotonergic Behaviors Evoked by 2,5-Dimethoxy-4-iodo-amphetamine in Mice via Inhibition of PKCδ-Mediated Mitochondrial Dysfunction

It has been recognized that serotonin 2A receptor (5-HT_2A) agonist 2,5-dimethoxy-4-iodo-amphetamine (DOI) impairs serotonergic homeostasis. However, the mechanism of DOI-induced serotonergic behaviors remains to be explored. Moreover, little is known about therapeutic interventions against serotonin syndrome, although evidence suggests that ginseng might possess modulating effects on the serotonin system. As ginsenoside Re (GRe) is well-known as a novel antioxidant in the nervous system, we investigated whether GRe modulates 5-HT_2A receptor agonist DOI-induced serotonin impairments. We proposed that protein kinase Cδ (PKCδ) mediates serotonergic impairments. Treatment with GRe or 5-HT_2A receptor antagonist MDL11939 significantly attenuated DOI-induced serotonergic behaviors (i.e., overall serotonergic syndrome behaviors, head twitch response, hyperthermia) by inhibiting mitochondrial translocation of PKCδ, reducing mitochondrial glutathione peroxidase activity, mitochondrial dysfunction, and mitochondrial oxidative stress in wild-type mice. These attenuations were in line with those observed upon PKCδ inhibition (i.e., pharmacologic inhibitor rottlerin or PKCδ knockout mice). Furthermore, GRe was not further implicated in attenuation mediated by PKCδ knockout in mice. Our results suggest that PKCδ is a therapeutic target for GRe against serotonergic behaviors induced by DOI.

Serotonin Syndrome and the Anaesthetist

Serotonin syndrome results from excessive activation of serotonin (5-hydroxytryptamine; 5-HT) receptors in the nervous system, on the surface of platelets, and on the vascular endothelium. The clinical manifestations are a triad of altered conscious state, autonomic dysfunction, and neuromuscular excitability. Clinical diagnostic criteria remain poorly defined and unvalidated, and there are no available investigations to confirm the diagnosis. The syndrome is caused by the administration of one or more drugs possessing serotonergic activity. Severe forms of the syndrome usually result from overdose, but can be induced by monotherapy. The exact incidence of serotonin syndrome remains unknown, but is likely to be increasing due to increased prescription of selective serotonin reuptake inhibitor anti-depressants and tramadol, as well as recreational use of amphetamine-like substances. Serotonin syndrome may complicate the administration of drugs frequently used in anaesthetic practice, including pethidine and tramadol. Although the majority of cases improve with symptomatic and supportive care, severe cases need intensive care and frequently require mechanical ventilation. Neuromuscular excitability is likely to be the cause of rhabdomyolysis seen in severe cases and should be treated with benzodiazepines and muscle relaxants. Supportive therapies are required to treat hyperthermia and autonomic dysfunction. Cyproheptadine is the most commonly administered serotonergic antagonist, but is unavailable in parenteral form.

Malignant Syndrome and Serotonin Syndrome in a General Hospital Setting: Clinical Features, Frequency and Prognosis

Objective The differences in the frequency and clinical features of malignant syndrome (MS) and serotonin syndrome (SS) in same population have only rarely been reported. To report the frequency and clinical features of MS and SS in a general hospital setting. Methods The clinical and laboratory features of patients with MS and those with SS, who were consecutively admitted to Chiba Rosai Hospital, during the past 4.5 years were reviewed. Results Of the 2005 patients admitted, MS was observed in 16 patients (0.8%) and SS in 2 (0.1%). In the 16 patients with MS, the underlying disorder included depression (n = 5), and dementia or parkinsonism (n = 11). The underlying etiology of the 2 patients with SS was depression. In 5 patients, MS was difficult to distinguish from SS because of overlapping symptoms and signs and/or treatments with both neuroleptic and serotoninergic drugs. Of the 16 patients with MS, 1 died, 1 remained wheelchair-bound, 4 were able to walk with assistance, and 10 regained their ability to ambulate independently. The 2 patients with SS recovered after cyproheptadine therapy and were discharged on foot. Conclusion MS occurs more frequently than SS in the general hospital setting. Underlying aetiologies in patients with MS were more common due to dementia or parkinsonism than in patients with psychiatric disorders. The differential diagnosis of MS and SS is often difficult and the diagnostic sensitivities largely differ for each of the diagnostic criteria. As a result, the establishment of new diagnostic criteria that specifically focus on distinguishing MS from SS is therefore required.

Serotonin Syndrome Induced by Fluvoxamine and Oxycodone

Objective:

To report a case of severe serotonergic symptoms following the addition of oxycodone to fluvoxamine.

Case Summary:

A 70-year-old woman developed severe serotonergic features, including confusion, nausea, fever, clonus, hyperreflexia, hypertonia, shivering, and tachycardia, following the addition of oxycodone 40 mg twice daily to fluvoxamine 200 mg/day, easily fulfilling diagnostic criteria for serotonin syndrome. Discontinuation of the offending drugs resulted in resolution of her symptoms over 48 hours, and no other cause of the syndrome was identified. Use of the Naranjo probability scale indicated a probable relationship between the serotonergic symptoms and the addition of oxycodone to fluvoxamine therapy.

Discussion:

Serotonin syndrome is a serious adverse reaction usually due to interactions with serotonergic drugs. There have been only 3 previous reports involving oxycodone. Most previous reports of serotonin syndrome involving analgesics have been associated with meperidine, dextromethorphan, and tramadol. Unlike these synthetic opioids, however, oxycodone does not inhibit the reuptake of serotonin. In addition, there are a number of other possible pharmacologic mechanisms for the interaction we observed.

Conclusions:

Monitoring for serotonergic adverse events should be done when oxycodone is given to patients receiving serotonin-reuptake inhibitors.

Combination of Escitalopram and Rasagiline Induced Serotonin Syndrome: A Case Report and Review Literature

BACKGROUND

Serotonin syndrome is a rare but potentially fatal complication of drugs that have effects on central nervous system serotonin. It is characterized by sudden onset of altered mental status, increased neuromuscular activity, and autonomic instability.

CASE REPORT

The authors reported a case of serotonin syndrome associated with combined therapy of monoamine oxidase-B inhibitors and selective serotonin reuptake inhibitor A 77-year-old Thai man had been taking escitalopram for depression for three years. He presented with high-grade fever and confusion two days after taking rasagiline for Parkinson's disease. He also had agitation, hallucination, and behavioral change. Escitalopram and rasagiline were discontinued but his renal function worsened, turning to acute kidney injury. He was diagnosed as serotonin syndrome.

CONCLUSION

This is the first case report of serotonin syndrome due to combination of escitalopram and rasagiline used.

[The serotonin syndrome: why should cardiologists be aware and scared of it]

The serotonin syndrome (SS) represents a life-threatening adverse drug reaction, caused by serotonin overload in the central and peripheral nervous system, producing autonomic instability, neuromuscular and cardiovascular abnormalities, and cognitive alterations. The incidence of SS has been growing over the last few years, as a consequence of population aging and the steadily increasing use of pro-serotoninergic agents in clinical practice, in the presence of various comorbidities, mainly cardiovascular. Cardiologists often use combination therapies including serotoninergic agents, and should therefore consider the risk of serotoninergic adverse events caused by inappropriate drug interactions. SS is often difficult to diagnose and may be life-threatening if not adequately managed. Considering the several published case reports of overdose or not recommended associations, a greater awareness by clinicians about the potential risks associated with inappropriate use of these drugs is needed, as well as better information on the clinical features and therapeutic approaches to SS.

Ecstasy use and serotonin syndrome: a neglected danger to adolescents and young adults prescribed selective serotonin reuptake inhibitors

BACKGROUND

At present, there are scarce clinical and basic lab data concerning the risk of acute serotonin toxicity from selective serotonin reuptake inhibitors (SSRIs) and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) co-administration. The health care community can strongly benefit from efforts to address the high risks associated with serotonin syndrome from this specific drug combination.

OBJECTIVE

The aim of this work is to review the risk of serotonin syndrome in adolescents and young adults prescribed with SSRIs and are concurrently using ecstasy.

DATA SOURCES

An electronic search of the major behavioral science bibliographic databases (Pubmed, PsycINFO, Medline) was conducted to retrieve peer-reviewed articles, which detail the clinical characteristics, biological mechanisms and social implications of SSRIs, MDMA, and their potential synergism in causing serotonin syndrome in the pediatric and young adult population. Search terms included "serotonin syndrome", "ecstasy", "MDMA", "pediatric", and "SSRI". Additional references were incorporated from the bibliographies of these retrieved articles.

RESULTS

MDMA, in combination with the widely-prescribed SSRI antidepressant class, can lead to rapid, synergistic rise of serotonin (5-HT) concentration in the central nervous system, leading to the acute medical emergency known as serotonin syndrome. This review addresses such complication through an exploration of the theoretical mechanisms and clinical manifestations of this life-threatening pharmacological interaction.

CONCLUSION

The increasing incidences of recreational ecstasy use and SSRI pharmacotherapy among multiple psychiatric disorders in the adolescent population have made this an overlooked yet increasingly relevant danger, which poses a threat to public health. This can be curbed through further research, as well as greater health care provision and attention from a regulatory body owing.

Serotonin syndrome

Serotonin syndrome is a potentially serious clinical condition. In this article, the authors put serotonin syndrome into historical context, discuss its pathophysiology, review in detail its clinical presentations, diagnostic criteria, differential diagnosis and treatment. Special attention is given to drugs that most often cause serotonin syndrome, and the gene polymorphisms involved in the metabolism of these drugs.

Prolonged serotonin toxicity with proserotonergic drugs in the intensive care unit

Serotonin toxicity secondary to drug therapy, interaction or overdose is an increasing phenomenon worldwide. A proportion of patients require admission to an intensive care unit, but the treatment needed is usually supportive and of short duration. Prolonged ICU admission to control ongoing or long-lasting serotonin toxicity has not been reported previously. We describe three patients with prolonged serotonin toxicity, lasting 12-18 days. Symptoms of toxicity were easily demonstrable in each and were refractory to currently recommended therapies. We review the pharmacological mechanisms that led to prolonged serotonin toxicity in these patients. Predictors for prolonged serotonin toxicity include involvement of irreversible monoamine oxidase inhibitors (MAOIs) or slow-release preparations resistant to the effects of activated charcoal (eg, lithium). We also discuss the implications of prolonged toxicity for critical care management, to maintain optimal patient outcomes.

Assessment of 5-hydroxytryptamine efflux in rat brain during a mild, moderate and severe serotonin-toxicity syndrome

Serotonin (5-hydroxytryptamine; 5-HT)-toxicity syndrome, an iatrogenic brain disorder induced by excessive efflux of 5-HT, has received much attention because of increasing incidents of serotonergic antidepressants. However, the neural mechanism by which extracellular 5-HT is elevated to a toxic level for the syndrome remains to be determined. The goal of the present study was to test the hypothesis that extracellular 5-HT is composed of two component effluxes responsible for distinct aspects of the syndrome. The first set of experiments was to characterize the syndrome by measuring changes in neuromuscular signs, body-core temperature and mortality rate. Our results indicate that the syndrome severity can be categorized into mild, moderate and severe levels. The second set of experiments was to determine a threshold of extracellular 5-HT for induction of each level of the syndrome. Our results demonstrate that there were an 11-fold increase in the mild syndrome and an over 55-fold increase in the severe syndrome. In the last series of experiments, the excessive increases in 5-HT were pharmacologically separated into primary and secondary component effluxes with the 5-HT2A receptor antagonists cyproheptadine and ketanserin and NMDA receptor antagonist (+)-MK-801. Our results suggest that the primary component efflux was caused by direct drug effects on 5-HT biosynthetic and metabolic pathways and secondary efflux ascribed to indirect drug effect on a positive-feedback circuit involving 5-HT2A and NMDA receptors. In summary, the primary efflux could be an initial cause for the induction of the syndrome while the secondary efflux might involve deterioration of the syndrome.

[Iatrogenic movement disorders]

This does not pretend to be an exhaustive review of iatrogenic movement disorders. We present the main usual clinical presentation of abnormal movement related to drugs exposition with a special mention of the most serious side effects: the irreversible ones (tardives), and those potentially lethals (malignant neuroleptic syndrome and serotonin syndrome).

Linezolid-associated peripheral and optic neuropathy, lactic acidosis, and serotonin syndrome

Linezolid is an oxazolidinone antibacterial agent indicated for serious gram-positive infections. Only minor adverse effects were seen in phase III trials. However, more serious adverse effects were reported after commercial release, including cases of lactic acidosis, peripheral and optic neuropathy, and serotonin syndrome. Peripheral and optic neuropathy was usually seen after several months of linezolid therapy (median 5 mo), lactic acidosis after several weeks (median 6 wks), and serotonin syndrome after several days (median 4 days). Death occurred in two of seven reported cases of lactic acidosis, and three of 15 reported cases of serotonin syndrome. Improvement or complete recovery occurred in all cases of optic neuropathy, whereas complete recovery failed to occur in any patient with peripheral neuropathy. Linezolid should be discontinued immediately in patients experiencing these adverse effects. Patients receiving linezolid for more than 28 days should be monitored for signs of peripheral and optic neuropathy.

Mild serotonin syndrome associated with concurrent linezolid and fluoxetine

PURPOSE

A case of serotonin syndrome that developed during concurrent linezolid and fluoxetine is presented.

SUMMARY

A 23-year-old white male patient was originally admitted to receive intravenous chemotherapy for acute myelogenous leukemia. He had a history of intravenous amphetamine abuse, hepatitis B virus infection, hepatitis C virus infection, depression, and bipolar disorder. The patient's routine medications before admission included methadone, fluoxetine, voriconazole, transdermal nicotine patch, lorazepam, and quetiapine. The patient developed persistent neutropenia and complications from chemotherapy, including mild mucositis. Despite treatment with levofloxacin, acyclovir, and voriconazole, the patient developed high fevers. Levofloxacin was discontinued and aztreonam and vancomycin were started. After a blood culture revealed that the bacteria were likely vancomycin resistant, vancomycin was discontinued and linezolid was initiated. Nine hours later, the patient began complaining of severe pain in his abdomen. After a total of four doses of linezolid, the patient reported further discomfort. Two days after linezolid initiation, a health care team member identified the interaction between fluoxetine and linezolid as the cause of the patient's symptoms, and linezolid was discontinued. All symptoms resolved within 48 hours. While resolution generally occurs within 24-48 hours after discontinuing the offending agent, the time to resolution may be delayed if the agent has a long half-life or active metabolites, in which case admission to an intensive care unit is recommended. Cyproheptadine and chlorpromazine may also be used to treat symptoms.

CONCLUSION

Serotonin syndrome developed in a patient taking concurrent linezolid and fluoxetine.

The serotonin syndrome, triptans, and the potential for drug-drug interactions

The serotonin syndrome is an acute adverse reaction to medications that enhance serotonergic activity. The severity of cases ranges from mild to fatal. Recently, the U.S. Food and Drug Administration issued an alert that the risk of developing serotonin syndrome may be increased by the concomitant administration of triptan medications with certain other medications. However, a review of published data does not allow an accurate assessment of such risks related to triptans. We conclude that it is currently unclear whether administration of triptans with other serotonergic medications increases the risk of serotonin syndrome.

Das Serotoninsyndrom

The serotonin syndrome is caused by a drug-induced increase of the intrasynaptic serotonin concentration. Milder forms of the syndrome may be difficult to diagnose because of the variability of symptoms. Severe forms often rapidly turn into a life-threatening situation, therefore the serotonin syndrome may be a challenge for physicians. We describe the pathophysiology and therapeutic options of the serotonin syndrome and report about a 42-year-old female patient who ingested large amounts of moclobemide, a monoamine oxidase inhibitor, and citalopram, a selective serotonin reuptake inhibitor, for attempted suicide. Within a few hours the patient developed a lethal serotonin syndrome although ICU therapy was initiated immediately.

Serotonin syndrome

Serotonin syndrome is a preventable, drug-related complication that results from increased brainstem serotonin activity, usually precipitated by the use of one or more serotonergic drugs. Its clinical presentation consists of autonomic dysfunction, alteration in mental status, and neuromuscular disorder. Early recognition and treatment is important, because this condition is potentially fatal. Management includes withdrawal of causative agents and supportive measures such as hemodynamic stabilization, sedation, temperature control, hydration, and monitoring for complications. Serotonin antagonists, specifically cyproheptadine, have been used, but the documented benefits are purely anecdotal.

[Life-threatening serotonin syndrome following a single dose of a serotonin reuptake inhibitor during maintenance therapy with a monoamine oxidase inhibitor]

A 72-year-old man presented to the emergency clinic with motor restlessness and diminished consciousness 24 hours after he had mistakenly been given venlafaxine. He was referred from the psychiatric clinic where he was treated with tranylcypromine. Shortly after arrival, a severe serotonin syndrome developed with generalised myoclonic seizures, hyperreflexia, hypertonia, a rapid increase in temperature to 40.9 degrees C, hypertension, tachycardia, respiratory insufficiency, hyperkalaemia and metabolic acidosis. The patient was treated with the sedative propofol and the muscle relaxant rocuronium, followed by intubation and artificial respiration. He was cooled on a cooling mattress. Twenty-four hours later the airway tube could be removed and after 48 hours he was returned to the psychiatric ward in good condition. Tranylcypromine is a monoamine oxidase inhibitor and venlafaxine is a serotonin and noradrenaline reuptake inhibitor. When two serotoninergic agents are combined, the serotonin syndrome may develop, and this may be life-threatening. The treatment of this syndrome with propofol and rocuronium can be given quickly and safely in practically every hospital.

The pathophysiology of serotonin toxicity in animals and humans: implications for diagnosis and treatment

Serotonin toxicity (or serotonin syndrome) has become an increasingly common and important clinical problem in medicine over the last 15 years with the introduction of many new antidepressants that can cause increased levels of serotonin (5-HT) in the central nervous system (CNS). Severe and life-threatening cases are almost exclusively a result of combinations of antidepressants (usually monoamine oxidase inhibitors and selective serotonin reuptake inhibitors). Unfortunately, the term serotonin syndrome has a number of quite different meanings, and many people writing on this subject have failed to differentiate them. This has led to false conclusions regarding the 5-HT receptor subtypes responsible for the life-threatening effects in animal and human toxicity, and suggestions of ineffective treatment strategies. This review primarily addresses the serotonin receptor subtypes that underlie the clinical manifestations of excess CNS serotonin in humans and animals, and their implications for diagnosis and treatment. More specific diagnostic criteria for serotonin toxicity are required to identify situations when specific antidotes are likely to be useful. However, the mainstay of treatment of severe cases is good supportive care and early intubation and paralysis in life-threatening serotonin toxicity.

Increased responsiveness to MDMA in adult rats treated neonatally with MDMA

MDMA [(+/-)3,4-methylenedioxymethamphetamine, also known as ecstasy] is a popular recreational drug among women of reproductive age. The objective of this study was to investigate the long-term neurobehavioral consequences of early developmental MDMA exposure. On postnatal days (PD) 1-4, Sprague-Dawley rats received two 10 mg/kg injections of MDMA with an inter-dose interval of 4 h. Male subjects were tested in adulthood for their performance in an object-recognition memory task and for their thermal and behavioral responses to an acute MDMA challenge (10 mg/kg i.p.). Neonatal MDMA administration did not alter working memory in the object-recognition test in young adulthood (PD 68-73) and there were no differences in radiolabeled citalopram binding to the serotonin transporter at this age. However, the pretreated animals showed increased thermal dysregulation and serotonin syndrome responses (particularly headweaving stereotypy) following the MDMA challenge. These results add to the growing literature demonstrating that developmental MDMA administration can lead to long-lasting functional abnormalities, and they further suggest that the offspring of ecstasy-using women may be at risk for enhanced sensitivity to this drug due to their earlier exposure.

Serotonin syndrome:case report and current concepts

Selective serotonin reuptake inhibitors (SSRI's) are increasingly being used as the first line therapeutic agent for the depression. It is therefore not unusual to see a case of overdose with these agents. More commonly an adverse drug reaction may be seen among the older patients who are particularly vulnerable to the serotonin syndrome due to multiple co-morbidity and polypharmacy. The clinical picture of serotonin syndrome (SS) is non-specific and there is no confirmatory test. SS may go unrecognized because it is often mistaken for a viral illness, anxiety, neurological disorder or worsening psychiatric condition.

Serotonin Toxicity Associated with Concomitant Use of Linezolid

OBJECTIVE:

To report 2 cases of serotonin toxicity (ST) associated with concomitant use of linezolid and serotonergic drugs and review previously published case reports.

CASE SUMMARIES:

Case 1. A 38-year-old white female with cystic fibrosis treated with venlafaxine 300 mg/day for one year was prescribed linezolid 600 mg intravenously every 12 hours for treatment of methicillin-resistant Staphylococcus aureus (MRSA) pulmonary infection. She displayed symptoms of ST 8 days after the introduction of linezolid. The venlafaxine dosage was decreased to 150 mg/day, and symptoms gradually abated over 36 hours. Case 2. A 37-year-old male with multiple myeloma received citalopram 40 mg/day and trazodone 150 mg/day for anxiety-related disorders. Linezolid treatment with 600 mg orally twice daily was instituted for MRSA cellulitis. The following day, the patient developed anxiety, panic attacks, tremors, tachycardia, and hypertension that persisted throughout linezolid treatment. Symptoms finally waned 5 days after linezolid treatment was stopped.

DISCUSSION:

The symptoms observed in our patients were consistent with Sternbach's criteria for ST. A review of published case reports showed a short time to onset of symptoms following the introduction of linezolid, generally within 1–3 days. Also of note is the use of relatively high dosages of serotonergic drugs. Use of the Naranjo probability scale indicated a possible relationship between the use of linezolid and the occurrence of ST in both cases.

CONCLUSIONS:

Clinicians should pay special attention to patients treated with serotonergic drugs, especially those receiving dosages in the higher end of the normal range who are prescribed linezolid, and consider tapering or reducing the dosage of serotonergic drugs for the duration of antibiotic therapy.

Partial 5-HT(1A) receptor agonist activity by the 5-HT(2C) receptor antagonist SB 206,553 is revealed in rats spinalized as neonates

Modification of spinal serotonergic receptors caudal to spinal injury occurs in rats that received spinal cord transections as neonates. Evaluation of the serotonin syndrome, a group of motor stereotypies elicited by serotonergic (5-HT) agents in 5-HT-depleted animals, and open field locomotor behavior were used to assess behavioral consequences of injury and treatment. We extend these findings to show that a partial 5-HT(1A) agonist activity is revealed by the 5-HT(2C) receptor antagonist (SB 206,553) in this animal model, as measured by evaluation of serotonin syndrome behavior. Treadmill stimulation enhances this motor response, caudal to the injury, in the hindlimbs and tail. These results imply a broader modification of serotonergic receptors than previously thought and suggest a potential strategy by which serotonergic agents may enhance functional recovery following neonatal injury.

[Serotonin syndrome: report of two cases and review of the literature]

INTRODUCTION

Serotonin is a neurotransmitter synthesized from tryptophan. It is implied in the regulation of mood, cognition, sleep cycle, synthesis of cerebrospinal fluid, and other processes. Generally, it is implied in human pathology by hypofunction. However, there is a complication of unknown incidence related to treatment with drugs that increase the stimulation of 5-HT1A serotonin receptors, called serotonin syndrome (SS). Clinically, it is characterised by the presence of a triad of mental and autonomic disorders, and motor hyperactivity. This entity has not biological markers and its diagnosis could be done verifying the proposed criteria.

CASE REPORTS

Two cases of SS are presented, one of them related to the combination of risperidone and sertraline, as first report in the literature. Both cases had a favourable outcome employing support measures.

CONCLUSIONS

The physiopathology, the diagnosis, the differential diagnosis, and the treatment are reviewed. We emphasize the potentially high frequency of this disorder, given the growing use of serotonin activity modifying drugs, and the typically benign course of the SS once the support measures are started.

Movement disorder emergencies

Movement disorders may present acutely, and failure to recognize and exclude important differential diagnoses can result in significant morbidity or mortality. Unfortunately, much of the literature pertaining to this topic is scattered and not easily accessible. This review aims to address this deficit. Movement disorder emergencies are discussed according to their most likely mode of presentation. Diagnostic considerations and early management principles are reviewed, along with appropriate pathophysiology where relevant.

Relative Toxicity of Selective Serotonin Reuptake Inhibitors (SSRIs) in Overdose

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) have increasingly replaced tricyclic antidepressants (TCAs) in the treatment of depression. They appear to be safer in overdose, but there is little information on their spectrum of toxicity in overdose, or relative toxicity of each agent.

OBJECTIVE

To determine the effect of SSRIs in overdose, as a group, and the relative toxicity of five different SSRIs.

METHODS

A review of consecutive SSRI poisoning admissions to a single toxicology unit. Outcomes examined were length of stay [LOS], intensive care [ICU] admission rate, coma, seizures, electrocardiographic [ECG] abnormalities, and presence of serotonin syndrome [SS]. Logistic regression was used to model the outcome QTc >440 msec.

RESULTS

There were 469 SSRI poisoning admissions analyzed after exclusions. The median LOS for all SSRI overdose admissions was 15.3 h (IQR: 10.5-21.3) and 30 of 469 (6.4%; 95% CI 4.3-9.0%) cases were admitted to ICU. The incidence of seizures was 1.9% and coma was 2.4%. Serotonin syndrome occurred in 14% of overdoses. Comparison of median QTc intervals of the five SSRIs was significantly different (p=0.0002); citalopram (450 IQR: 436-484) was individually different to fluoxetine (p=0.045), fluvoxamine (p=0.022), paroxetine (p=0.0002), and sertraline (p=0.001). The proportion of citalopram overdoses with a QTc >440 msec was 68%, differing significantly from sertraline (adjusted OR: 5.11 95% CI 2.32-11.27). Comparison of median QT intervals of the five SSRIs was statistically different (p=0.026); citalopram (400 IQR: 380-440) was individually different from sertraline (p=0.023).

CONCLUSIONS

This study shows SSRIs are relatively safe in overdose despite serotonin syndrome being common. The exception was citalopram, which was significantly associated with QTc prolongation. We believe that cardiac monitoring should be considered in citalopram overdose, particularly with large ingestions and patients with associated cardiac disease.

Serotonin Syndrome with Elevated Paroxetine Concentrations

OBJECTIVE

To describe a case of serotonin syndrome due to paroxetine and ethanol.

CASE SUMMARY

A 57-year-old white man was brought to the emergency department one day after ingesting paroxetine 3600 mg and a pint of hard liquor. He denied the use of any other drug or herbal products and regular use of alcohol. Upon arrival to the hospital, vital signs were blood pressure 188/103 mm Hg, heart rate 114 beats/min, respiratory rate 28 breaths/min, temperature 36.8 °C, and O2 saturation 96% on room air. Findings on physical examination included dilated pupils, facial flushing, diaphoresis, shivering, myoclonic jerks, tremors, and hyperreflexia. A tentative diagnosis of serotonin syndrome was made. Initially, cyproheptadine 8 mg was administered orally with no observable effect. An additional 12 mg was given in 3 doses over 24 hours. Symptoms abated slowly over the next 6 days, during which a thorough evaluation failed to reveal any other potential causes for the patient's condition. Serum paroxetine concentrations at 27.5 and 40 hours after ingestion were 1800 and 1600 ng/mL, respectively (normal 20–200 ng/mL).

DISCUSSION

Serotonin syndrome is rarely reported in patients taking only one serotonergic medication. Although serum paroxetine concentrations have not been shown to correlate with efficacy or toxicity, our patient's serum paroxetine concentration was 9 times the upper end of the therapeutic range. Cyproheptadine, which has been suggested as a therapy, did not appear beneficial in this patient. Use of the Naranjo probability scale indicated a probable relationship between the serotonin syndrome and the overdose of paroxetine taken by this patient.

CONCLUSIONS

More studies are needed to better assess the role of cyproheptadine and other serotonin antagonists in the management of the serotonin syndrome. Regardless of the use of cyproheptadine or other agents, attention should be paid to fluid status, decontamination, and management of hyperthermia, agitation, and seizures.

Diazepam and chlormethiazole attenuate the development of hyperthermia in an animal model of the serotonin syndrome

The serotonin (5-HT) syndrome is the most serious toxic interaction of antidepressants, but no pharmacotherapy has yet been established. In the present study, we created an animal model of the 5-HT syndrome by intraperitoneally injecting rats with clorgyline (2 mg/kg) and 5-hydroxy-L-tryptophan (5-HTP) (100 mg/kg) and evaluated the effectiveness of potent 5-HT(2A) receptor antagonists and GABA-enhancing drugs, including diazepam and chlormethiazole. The rectal temperature of the rats was measured, and the noradrenaline (NA) and 5-HT levels in the anterior hypothalamus were measured by microdialysis. In the group pre-treated with saline, the rectal temperature increased to more than 40 degrees C, and all of the animals died within 90 min after administration. Pre-treatment with potent 5-HT(2A) receptor antagonists prevented the development of hyperthermia and death in the rats. Pre-treatment with diazepam, 10 and 20mg/kg, and chlormethiazole, 50 and 100mg/kg, attenuated the development of hyperthermia. Although neither of these drugs completely prevented the rats from dying, they prolonged their survival time. Regardless of the type of therapeutic agents, the concentration of 5-HT increased to about 1100-fold the pre-administration level. The NA levels in the saline group increased to about 16-fold the pre-administration levels, but the increase was significantly lower in the rats that survived as a result of drug therapy. These results suggest that GABA-mimetic drugs may be effective against the 5-HT syndrome, although they have a somewhat weaker effect than the potent 5-HT(2A) receptor blockers, and that not only is 5-HT activity increased in the brain in the 5-HT syndrome, but the NA system is also enhanced.

Functional study of rat 5-HT2A receptors using antisense oligonucleotides

We studied the effects in rats of a 6-day intracerebroventricular (i.c.v) infusion of four different end-capped phosphorothioate-modified antisense oligonucleotides (AOs), specifically targeting different regions of the 5-hydroxytryptamine2A (5-HT2A) receptor mRNA, on central 5-HT2A receptor expression and 5-HT2A receptor-mediated behaviours. Only one of the AOs (sequence 4), directed against the 5'-untranslated region (from + 557 to + 577), specifically affected central 5-HT2A receptor expression and receptor-mediated behaviour. This AO (sequence 4) reduced binding of the 5-HT2A agonist 1-(2,5-dimethoxy-4-[125I]iodophenyl)-2-aminopropane ([125I]DOI) up to 25% in cortical areas, as measured by quantitative autoradiography. Cortical binding of the antagonist [3H]ketanserin was not affected. As the specific AO treatment presumably affects the synthesis of new receptor, we hypothesize that this newly synthesized receptor represents the major part of the functionally active, G protein coupled receptor. A 5-day infusion of AO (sequence 4) resulted in profound inhibition of the head-twitch response (HTR) to 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM). In contrast, treatment with vehicle, sense oligonucleotides (SOs) and other AOs (sequences 1, 2 and 3) caused an increased DOM-induced HTR as well as a spontaneous HTR. The latter was abolished by treatment with the 5-HT2 receptor antagonist, ritanserin. Systematic investigation of the surgical and infusion procedures revealed that the enhanced HTR already appeared following drilling of the skull. This wounding can probably damage the blood-brain barrier and cause a stress-induced increase in serotonergic transmission. AO (sequence 4) treatment also abolished the spontaneous HTR. AO (sequence 4) treatment allowed the identification of specific central 5-HT2A receptor-mediated behaviours in the complex serotonergic syndrome induced by tryptamine in rats. Only bilateral convulsions and body tremors were significantly inhibited. The backward locomotion, hunched back and Straub tail were not affected, nor was cyanosis, an index of vasoconstriction induced by peripheral 5-HT2A receptor activation. Labelling of central 5-HT2C receptors by [3H]mesulergine, and 5-HT2C receptor-mediated anxiety were not attenuated by AO or SO treatment. Rats treated with AO (sequence 4) showed increased locomotor activity and a strong reactivity towards touching. We hypothesize that the down-regulation of functional 5-HT2A receptors may shift the balance between various 5-HT receptor subtypes. Our analysis of the behavioural consequences of AO treatment and the use of different AOs and SOs has shown that specific receptor-mediated behaviour can be identified.

Serotonin syndrome and other serotonergic disorders

Serotonin syndrome is an iatrogenic disorder induced by pharmacologic treatment with serotonergic agents that increases serotonin activity. In addition, there is a wide variety of clinical disorders associated with serotonin excess. The frequent concurrent use of serotonergic and neuroleptic drugs and similarities between serotonin syndrome and neuroleptic malignant syndrome can present the clinician with a diagnostic challenge. In this article, we review the pathophysiology, diagnosis, and treatment of serotonin syndrome as well as other serotonergic disorders.

Neuroleptic withdrawal versus serotonergic syndrome in an 8-year-old child

There appears to be considerable symptomatic overlap between neuroleptic withdrawal reactions and the serotonin syndrome. This case report is of an 8-year-old boy who developed symptoms compatible with both conditions while discontinuing pimozide and starting fluoxetine. It illustrates how the use of neuroleptic medication in young children is not without the risk of serious adverse drug events and can complicate diagnostic issues. This case report supports the suggestion that adverse drug reactions related to neuroleptics and serotonergic agents could be part of the same clinical and neurophysiological spectrum.

Serotonin syndrome: a reported case

We describe a patient treated with SSRI and Ldopa, who developed agitation, rigidity, hyperreflexia, restlessness, autonomic instability, fever and finally death. CSF examination, MRI of the brain, laboratory investigations, except for serum CK, glycemia and WBC, were normal. His condition was thought to result from an central serotonin activity. The serotonin syndrome occurs following the use of serotomimetic agents (serotonin reuptake inhibitors, tricyclic and tetracyclic antidepressants, tryptophan alone or in combination with monoamine oxidase inhibitors).

Recreational Ecstasy/MDMA, the serotonin syndrome, and serotonergic neurotoxicity

The ring-substituted amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA) or "Ecstasy" is widely used a recreational drug. It stimulates the release and inhibits the reuptake of serotonin (5-HT) and other neurotransmitters such as dopamine to a lesser extent. The acute boost in monoamine activity can generate feelings of elation, emotional closeness, and sensory pleasure. In the hot and crowded conditions of raves/dances, mild versions of the serotonin syndrome often develop, when hyperthermia, mental confusion, and hyperkinesia predominate. Rest in a cooler environment generally reverses these problems, although they can develop into medical emergencies, which occasionally prove fatal. This acute serotonergic overactivity is exacerbated by the high ambient temperatures, overcrowding (aggregate toxicity), and use of other stimulant drugs. The on-drug experience is generally followed by negative moods, with 80--90% of weekend Ecstasy users reporting 'midweek blues', due probably to monoaminergic depletion. Single doses of MDMA can cause serotonergic nerve damage in laboratory animals, with repeated doses causing extensive loss of distal axon terminals. Huether's explanatory model for this 5-HT neurotoxicity will be briefly described. There is an increasing body of evidence for equivalent neuropsychobiological damage in humans. Abstinent regular Ecstasy users often show: reduced cerebrospinal 5-HIAA, reduced density of 5-HT transporters, blunted response to a fenfluramine challenge, memory problems, higher cognitive deficits, various psychiatric disorders, altered appetite, and loss of sexual interest. Functional deficits may remain long after drug use has ceased and are consistent with serotonergic axonal loss in higher brain regions.

Serotonin syndrome presenting as hypotonic coma and apnea: potentially fatal complications of selective serotonin receptor inhibitor therapy

OBJECTIVE

To describe a patient who developed serotonin syndrome on four separate occasions as a result of monotherapy with two different selective serotonin receptor inhibitors (fluoxetine and cetalopram).

DESIGN

Case report.

SETTING

Community hospital.

PATIENTS

Single patient with four episodes of serotonin syndrome.

MEASUREMENTS AND MAIN RESULTS

The syndrome was characterized by coma/unresponsiveness (four episodes), dilated pupils (four episodes), salivation (two episodes), dryness of mouth (two episodes), myoclonus like activity of eyelids (four episodes), oculogyric crisis (four episodes), flaccid paralysis of all extremities (four episodes), tremors (two episodes), apnea (two episodes), restlessness (one episode). Recovery occurred within 24 hrs, although muscle pain and weakness persisted for 2 months after stopping fluoxetine. Apnea occurred in both episodes associated with fluoxetine therapy.

CONCLUSION

Apnea and coma may occur in serotonin syndrome.