A Case Series of 11 Patients With Subacute Serotonin Syndrome.

BACKGROUND: Serotonin syndrome is an acute, life-threatening illness characterized by mental status changes, neuromuscular symptoms, and autonomic instability. Some patients taking serotonergic antidepressants have been noted to have unexplained mental status changes and/or neuromuscular changes without autonomic instability raising the possibility of a more chronic or attenuated form of serotonin syndrome. OBJECTIVE: Assessment of antidepressant blood levels to support the diagnosis of a subacute serotonin syndrome. METHODS: At a tertiary psychiatric outpatient clinic, patients with unexplained mental status and/or neuromuscular changes without autonomic instability had antidepressant blood levels assessed. RESULTS: Eleven patients were identified with signs and symptoms partially consistent with serotonin syndrome. Nine patients had cognitive changes, while four patients had motor changes, and three patients had psychosis. All patients had elevated blood levels of a single serotonergic antidepressant. Limited follow-up suggests that symptoms improve with reduction of antidepressant medication. CONCLUSIONS: These cases suggest that a more chronic, attenuated form of serotonin syndrome exists. Diagnostic criteria are proposed for a distinct clinical entity: subacute serotonin syndrome (SSS). Further research is required to validate these criteria. Clinicians should consider drawing antidepressant levels for patients with symptoms and signs suggestive of SSS-especially those at increased vulnerability for excessive serotonergic agonism. Given the high prevalence of antidepressant medication use, the awareness of SSS could lead to improved patient outcomes and public health.

Prevalence and Correlates of Serotonin Syndrome in Real-World Inpatients.

BACKGROUND: Serotonin syndrome (SS) is a potentially life-threatening adverse drug reaction due to an increased central and peripheral serotonin activity, which usually presents as a triad of behavioral changes, neuromuscular excitability, and autonomic instability. Probably SS is often misdiagnosed, and its symptoms are mistaken for psychiatric symptoms or general medical issues: the true incidence of SS is not clear, and literature concerning potential risk factors is scarce. Our aims were to examine the prevalence of SS in a naturalistic sample of hospitalized patients and to evaluate potential factors related to the risk of developing the condition. METHODS: The sample included 133 patients being treated with serotonergic medications admitted to the psychiatric inpatient unit of the San Luigi Gonzaga Hospital. All patients received a medical examination (including a neurological examination) within 24 hours of admission. Serotonin syndrome was diagnosed according to Hunter Criteria. RESULTS: Sixteen patients (12%) were diagnosed with SS. In the subgroup of subjects with SS, we found a higher rate of male patients when compared with subjects with no SS (62.5% vs 33.3%, P = 0.023). CONCLUSIONS: SS probably is an underestimated condition, which should be carefully assessed in patients on serotonergic medications. Male gender was the only factor found to be significantly related to a higher risk of developing SS. Further studies on larger samples are needed, to gain more information on possible risk factors and to identify subjects more prone to developing SS, given the potential risk for patients' health.

Serotonin syndrome: A pharmacovigilance comparative study of drugs affecting serotonin levels.

BACKGROUND: Serotonin syndrome is a rare and potentially fatal adverse drug reaction caused by serotonergic drugs and is due to an increase in serotonin concentration or activation of the 5-HT receptor in the central nervous system. We analysed adverse events in the US Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) data set to investigate the main drug classes related to reports of serotonin syndrome and the reporting risk in relation to age and sex. METHODS: We analysed data from the FAERS database to evaluate the main drug classes related to reports of the serotonin syndrome, and the reporting risk in relation to age and sex. RESULTS: We found 8,997 cases of serotonin syndrome; selective serotonin reuptake inhibitors (SSRIs) was the class of drugs with most reports, followed by opioids and other antidepressants. The highest Reporting Odds Ratios (ROR) for drug classes was for monoamine oxidase (MAO) inhibitors (45.99, 95% confidence interval (CI): 41.21-51.33) and SSRIs (32.66, 95% CI: 31.33-34.04), while the ten active substances with the highest ROR were moclobemide, isocarboxazid, oxitriptane, tranylcypromine, melitracen, phenelzine, linezolid, amoxapine, reboxetine and tryptophan; with values of ROR ranging from 44.19 (95% CI: 25.38-76.94) of tryptophan to 388.36 (95% CI: 314.58-479.46) of moclobemide. The ROR for the most commonly involved drugs was higher in the group of older adults (65 > years old), and higher in males. CONCLUSION: Prescribers need to be vigilant about drugs that can raise serotonin concentration or influence serotonergic neurotransmission, also when using drugs with less well-known risk for serotonin syndrome, like linezolid and triptans.

Real-world evaluation of linezolid-associated serotonin toxicity with and without concurrent serotonergic agents.

BACKGROUND: The risk of linezolid-associated serotonin toxicity remains unclear. This study sought to evaluate the incidence of serotonin toxicity among hospitalized patients who received linezolid with or without concurrent serotonergic agents (SAs). Secondary outcomes were to assess the dose, agent selection and number of SAs. METHODS: A single-centre, retrospective cohort study of hospitalized patients aged ≥18 years who received at least one dose of linezolid with or without SAs between 1 January 2014 and 30 June 2021 was performed. Patients were excluded if they were aged <18 years, had linezolid ordered but not administered, were pregnant or were incarcerated. Up to five concurrent SAs were assessed, and dose category was classed as low, moderate or high (dose <33%, 33-66% or >66% of maximum daily dose, respectively). Serotonin toxicity was identified by searching patients' electronic medical records. If identified, the Sternbach criteria and Hunter criteria were applied. RESULTS: Of 2022 patients screened, 1743 were included in this study. Mean age, weight and linezolid duration were 58.5 years, 90.7 kg and 3.8 days, respectively. Approximately 67% (1168/1743) of patients received linezolid with at least one SA, and several patients received multiple SAs. Most patients (53.8%; 616/1144) received moderate- and/or high-dose SAs. Only two patients (0.11%) were identified as possible cases of serotonin toxicity based on the electronic medical record search. However, the incidence of serotonin toxicity was 0.06% (1/1743) based on the Sternbach criteria and 0% (0/1743) based on the Hunter criteria. CONCLUSIONS: Serotonin toxicity among hospitalized patients who received linezolid with or without SAs was exceedingly rare, even among those who received multiple and high-dose SAs.

Association of Linezolid With Risk of Serotonin Syndrome in Patients Receiving Antidepressants.

Importance: Linezolid has the potential to interact with some antidepressants, leading to serotonin syndrome. However, few empirical data support warnings for patients taking antidepressants to avoid linezolid. Objectives: To examine the incidence of serotonin syndrome in patients receiving oral linezolid and how concomitant antidepressant treatment changes this risk. Design, Setting, and Participants: This population-based, retrospective cohort study used linked administrative databases at ICES to collect data from outpatients 66 years or older in Ontario, Canada, who were prescribed oral linezolid for any duration from October 1, 2014, to January 1, 2021, with follow-up to 30 days (January 31, 2021). Exposures: The use of antidepressants while receiving linezolid therapy vs no antidepressant use while receiving linezolid therapy. Main Outcomes and Measures: The primary outcome was clinically significant serotonin syndrome based on a physician diagnosis, Sternbach criteria, or the Hunter Serotonin Toxicity Criteria within 30 days of starting oral linezolid treatment. Secondary outcomes were altered mental status, hospitalization, or death within 30 days of starting linezolid treatment. Results: The study included 1134 patients (age ranges, 66-69 years for 225 patients [19.8%], 70-79 years for 473 patients [41.7%], and ≥80 years for 436 patients [38.4%]; 595 [52.5%] male) who were prescribed linezolid. Of 1134 patients, 215 (19.0%) were also taking antidepressants. Serotonin syndrome occurred in fewer than 6 patients (<0.5%). The number of serotonin syndrome cases were fewer in the antidepressant group. In a propensity score-matched cohort, the adjusted risk difference for serotonin syndrome between the antidepressant group and the no antidepressant group was -1.2% (95% CI, -2.9% to 0.5%). There were similar rates of altered mental status, hospitalization, and death between the propensity score-matched groups. Conclusions and Relevance: In this cohort study of older patients who were prescribed linezolid, serotonin syndrome occurred rarely. Concurrent antidepressants did not significantly increase the risk of serotonin syndrome. These findings suggested that linezolid is likely safe for patients receiving antidepressants. Nevertheless, prescribers should remain vigilant for this potential drug interaction.

High risk and low prevalence diseases: Serotonin syndrome.

INTRODUCTION: Serotonin syndrome is a rare, frequently misdiagnosed, serious condition with high morbidity. OBJECTIVE: This review highlights the pearls and pitfalls of serotonin syndrome, including diagnosis, initial resuscitation, and management in the emergency department (ED) based on current evidence. DISCUSSION: Serotonin syndrome is a potentially deadly toxidrome marked by excess serotonin receptor activity or neurotransmission. Features of serotonin syndrome include 1) neuromuscular excitation such as tremor, hyperreflexia, and clonus; 2) autonomic dysfunction such as tachycardia, hypertension/hypotension, and hyperthermia; and 3) altered mental status such as agitation, delirium, and coma. Although serotonin syndrome may be more obvious in patients who have overdosed on serotonergic agents such as serotonin reuptake inhibitors (SSRIs), multiple other medications may also cause serotonin syndrome. Alternative diagnoses such as sepsis, neuroleptic malignant syndrome, and decompensated hyperthyroidism should be considered. The primary components of therapy include stopping the offending agent and supportive care, which focuses on agitation control, monitoring for and treating hyperthermia, and managing autonomic instability. CONCLUSIONS: An understanding of serotonin syndrome can assist emergency clinicians in diagnosing and managing this disease.

The prevalence of serotonin syndrome in an intensive care unit: A prospective observational study.

PURPOSE: In spite of life-threatening nature of serotonin syndrome (SS), it remains an under-diagnosed condition. The availability of epidemiological data about SS, especially in the ICU setting, may help physicians make early diagnoses and interventions. MATERIALS AND METHODS: This was a 6-month prospective study in a medical ICU of a tertiary hospital to find out the prevalence of SS. All consecutive adult patients admitted to the medical ICU were evaluated to see if they fulfilled the Hunter criteria of SS. Patients who met the Hunter criteria were evaluated further for other details. RESULTS: Overall, 309 patients were identified of which 24 (7.8%) met the Hunter criteria. The mean age was 52.4 years, and 75% were male. Most patients received two or more serotonergic drugs. Ondansetron was the most common serotonergic drug (58%), followed by tramadol (38%), and cough syrup (dextromethorphan or chlorpheniramine, 21%). None of the patients received a diagnosis of SS by the treating physicians. Chronic obstructive pulmonary disease exacerbation with respiratory failure and metabolic encephalopathy were the two most common admission diagnoses (17% each). Twenty-two patients received cyproheptadine. There were no fatalities. CONCLUSION: SS is not uncommon in the ICU setting. There is a need to increase awareness among physicians.

New psychoactive substances (NPS) and serotonin syndrome onset: A systematic review.

The use of several new psychoactive substances (NPS) has become very popular and is posing global health risks. Chemically and pharmacologically diverse molecules are constantly emerging and are presenting with a wide range of clinical implications. Serotonin toxicity, and specifically Serotonin Syndrome (SS), might develop as a result of an over-activation of the serotoninergic system caused by several mechanisms resulting in a classic triad of altered mental status, neuromuscular effects, and autonomic hyperactivity. In the present systematic review, we have investigated and summarized the available evidence related to the association between SS and NPS intake. Three retrospective studies, two case series and five case reports were included in this systematic review; several NPS were found to be implicated in SS occurrence These include psychedelic phenethylamines, e.g. 2, 5-dimethoxy-4-iodophenethylamine (2C-I); 2-(4-Iodo-2,5-dimethoxyphenyl)- N-I[(2-methyoxyphenyl)methyl]ethanamine (25I-NBOMe); and 5-(2-aminopropyl)indole (5-IT); and synthetic cathinones, e.g. mephedrone; 3,4-methylenedioxypyrovalerone (MDPV); methylone; butylone; NRG3; alpha-methyltryptamine (AMT); methoxphenidine (MXP); and the antidepressant bupropion. Bupropion was here misused at high dosages and/or in combination with other licit/illicit serotonergic drugs. Whilst most substances were ingested orally, nasal insufflation (with both 5-IT and 2C-I) and sublingual administration of blotter paper (with 25I-NBOMe) were reported as well. Interestingly, the psychiatric history was negative for most subjects, apart from two cases. Clinicians should be aware of NPS potential risks and the severe consequences of their recreational use, including SS. Also, due to their undetectability in routine and common drug screenings, the diagnostic challenges posed by NPS should not be underestimated during the treatment of such patients.

Serotonin syndrome by drug interactions with linezolid: clues from pharmacovigilance-pharmacokinetic/pharmacodynamic analysis.

PURPOSE: To characterize the post-marketing reporting of serotonin syndrome (SS) due to drug-drug interactions (DDIs) with linezolid and investigate the relationship with pharmacokinetic/pharmacodynamic (PK/PD) properties of serotonergic agents. METHODS: We queried the worldwide FDA Adverse Event Reporting System to extract SS records due to DDIs where linezolid was reported as suspect. For each serotonergic agent concomitantly reported, proportion of SS reports and mean number of DDIs were calculated and three different "SS reporting zones" were created. Relevant PK (peak concentration, area under plasma concentration curve, volume of distribution (VD), and lipophilicity) and PD (values of binding affinity (Ki) and IC50 for serotonin reuptake transporter (SERT) and 5-HT2A) parameters were extracted for each serotonergic agent, and relevant PK/PD indexes were calculated to assess correlation with mean number of DDIs (PV index). RESULTS: Six hundred sixty-nine reports of SS mentioning linezolid were found, being linezolid-citalopram (N = 69; 10.3%) the most frequently DDI reported. Citalopram and methadone showed respectively the highest proportion of SS reports (0.28%) and the lowest mean number of DDIs (1.41). Citalopram, escitalopram, and methadone emerged as red (i.e., alert)-zone medications: they exhibited high lipophilicity and large VD (proxies of excellent central nervous system penetration) coupled with high potency. Among PK/PD indexes, a significant correlation with PV index was found for VD/Ki SERT ratio (p = 0.05). DISCUSSION: Our integrated approach suggests that linezolid is more likely to cause SS when co-administered with citalopram, escitalopram, and methadone, as inferred from their pharmacological properties. Proper management of SS should be tailored on a case-by-case basis.

Adjunctive sertraline for asymptomatic cryptococcal antigenemia: A randomized clinical trial.

Cryptococcal antigen (CrAg) screening in HIV-infected persons with CD4 < 100 cells/µl can reduce meningitis and death, yet preemptive fluconazole therapy fails in ∼25%. Sertraline has in vitro and in vivo activity against Cryptococcus and is synergistic with fluconazole in mice. We evaluated the efficacy and safety of sertraline in asymptomatic cryptococcal antigenemia. We conducted a randomized trial of asymptomatic CrAg-positive Ugandans from November 2017 to February 2018. All subjects received WHO standard therapy of fluconazole 800 mg for 2 weeks, then 400 mg for 10 weeks, then 200 mg through 24 weeks. Participants were randomized to receive adjunctive sertraline or placebo, given in once-weekly escalating 100 mg/day doses up to 400 mg/day, which was then given for 8 weeks, then tapered. The primary endpoint was meningitis-free 6-month survival. The data and safety monitoring board halted the trial after 21 subjects were enrolled due to safety concerns. Meningitis-free 6-month survival occurred in 9 of 11 of placebo participants and 10 of 10 of sertraline participants. However, seven serious adverse events (SAEs) occurred (n = 4 sertraline group; n = 3 placebo group). Three SAEs in the sertraline group presented with psychosis and aggressive behavioral changes with one meeting Hunter's criteria for serotonin syndrome while receiving 200 mg/day sertraline. Two transient psychoses were associated with antecedent fluconazole and sertraline interruption. The serotonin syndrome resolved within 1 day, but psychosis persisted for 4 months after sertraline discontinuation. Sertraline was associated with excess SAEs of psychosis. Due to early stopping, we were unable to determine any efficacy for cryptococcal antigenemia.

Single-Agent Bupropion Exposures: Clinical Characteristics and an Atypical Cause of Serotonin Toxicity.

INTRODUCTION: Bupropion is the only Food and Drug Administration-approved synthetic cathinone. It increases the release of norepinephrine in the locus coeruleus and dorsal raphe nucleus, causing an increase in the frequency of serotonergic neuron firing. The diagnosis of serotonin toxicity (ST) from bupropion poisoning is controversial due to the lack of direct serotonergic activity. Nonetheless, there is one documented report of ST after single-agent bupropion overdose and multiple reports describing polypharmacy overdoses where bupropion may have contributed to ST. METHODS: This is a retrospective analysis of data collected by the Toxicology Investigators Consortium (ToxIC), a prospective multi-center toxico-surveillance and research network registry, from 2014 to 2017. Cases were identified if ST was a clinical effect and bupropion was the single agent listed. Data is presented descriptively. RESULTS: Of the 266 recorded single bupropion overdoses, the most common symptoms were seizures (47.1%), tachycardia (greater than 140 bpm) (33.9%), agitation (31.7%), toxic psychosis (20.4%), and myoclonus/tremor/hyperreflexia (19%). Benzodiazepines were the most common therapy (69.2%). Thirteen patients (5.9%) were diagnosed with ST by a medical toxicologist. CONCLUSION: Bupropion overdose is primarily associated with seizures, tachycardia, and agitation; bupropion may be an atypical cause of serotonin toxicity.

Serotonin Toxicity: Associated Agents and Clinical Characteristics.

BACKGROUND: Serotonin toxicity is a common cause of drug-induced altered mental status. However, data on the causes of serotonin toxicity, symptomatology, complications, and rate of antidotal treatment are limited. METHODS: This study evaluated cases of serotonin toxicity in the ToxIC registry, an international database of prospectively collected cases seen by medical toxicologists. Serotonin toxicity was diagnosed by bedside evaluation of medical toxicology specialists and explicit criteria were not used. The database was searched for "serotonin syndrome" between January 1, 2010, and December 31, 2016. RESULTS: There were 1010 cases included. Females made up 608 (60%) cases. Ages are as follows: younger than 2 years (3, 0.3%), 2 to 6 years (8, 0.8%), 7 to 12 years (9, 0.9%), 13 to 18 years (276, 27.3%), 19 to 65 years (675, 67%), older than 66 years (33, 3.4%), unknown (6, 0.6%). Reasons for encounter: intentional (768, 76%), adverse drug event/reaction (127, 12.6%), unintentional (66, 6%), and unknown (55, 5.4%). Signs/symptoms: hyperreflexia/clonus/myoclonus (601, 59.5%), agitation (337, 33.4%), tachycardia (256, 25.3%), rigidity (140, 13.9%), seizures (139, 13.7%), and hyperthermia (29, 2.9%). COMPLICATIONS: rhabdomyolysis (97, 9.7%), dysrhythmias (8, 0.8%), and death (1, 0.1%). TREATMENTS: benzodiazepines 67% (677/1010), cyproheptadine 15.1% (153/1010). There were 192 different xenobiotics reported with 2046 total exposures. Antidepressants were most common (915, 44.7%) with bupropion the most frequent overall (147, 7.2%). Common non-antidepressants were dextromethorphan (95, 6.9%), lamotrigine (64, 3.1%), and tramadol (60, 2.9%). DISCUSSION: Serotonin toxicity most often occurred in adult patients with intentional overdose. Antidepressants were the most common agents of toxicity. Interestingly, bupropion, a norepinephrine/dopamine reuptake inhibitor, was the most frequently mentioned xenobiotic. Though often cited as a potential antidote, only 15% of patients received cyproheptadine. Severe toxicity was rare. A single death was reported.

The Serotonin Syndrome: From Molecular Mechanisms to Clinical Practice.

The serotonin syndrome is a medication-induced condition resulting from serotonergic hyperactivity, usually involving antidepressant medications. As the number of patients experiencing medically-treated major depressive disorder increases, so does the population at risk for experiencing serotonin syndrome. Excessive synaptic stimulation of 5-HT2A receptors results in autonomic and neuromuscular aberrations with potentially life-threatening consequences. In this review, we will outline the molecular basis of the disease and describe how pharmacologic agents that are in common clinical use can interfere with normal serotonergic pathways to result in a potentially fatal outcome. Given that serotonin syndrome can imitate other clinical conditions, an understanding of the molecular context of this condition is essential for its detection and in order to prevent rapid clinical deterioration.

An 11-year retrospective review of cyproheptadine use in serotonin syndrome cases reported to the California Poison Control System.

WHAT IS KNOWN: Cyproheptadine is a serotonin and histamine antagonist that has been suggested as a treatment for serotonin syndrome in case reports. OBJECTIVE: We sought to examine the differences between outcomes and treatment recommendations in patients who received and did not receive cyproheptadine for a probable serotonin syndrome. METHODS: A retrospective review of cases reported to the California Poison Control System between 2006 and 2017 involving cyproheptadine administration or consideration for treatment of a probable serotonin syndrome. RESULTS AND DISCUSSION: A total of 1420 cases were identified and 288 cases met the inclusion criteria. Of these, 68 (23.1%) patients received cyproheptadine treatment and were significantly older (mean age 49.7 vs 33.5 years, P < 0.00001), intubated (n = 35, 51% vs n = 62, 28%, P < 0.05) and, although not statistically significant, were more frequently admitted to a critical care unit (n = 56, 82.3% vs n = 154, 70.0%, P = 0.09). There were no significant differences in serious outcomes (moderate or worse effects) or hospitalization rates (OR, 1.09, 95% CI, 0.49-2.64 and OR, 1.99, 95% CI, 0.86-4.58). There were eight fatalities, of which two patients received cyproheptadine. All fatalities were acute polypharmacy ingestions and had manifested severe symptoms (seizures, hypotension or hyperthermia) either prior to the administration or consideration of cyproheptadine therapy. Cyproheptadine was not administered in 138 (48%) cases primarily due to minimal clinical severity and patient improvement (43%), and not recommended in 82 (28%) cases for reasons from waiting for response to other supportive measures (30%), limited evidence of efficacy (28%) and undetermined diagnosis (14.6%). WHAT IS NEW AND CONCLUSION: The benefits of and indications for cyproheptadine are uncertain and questionable for the management of a serotonin syndrome. Future recommendations on its use should be based on diagnostic criteria, severity of symptoms and management in conjunction with other supportive measures.

Association of Coprescription of Triptan Antimigraine Drugs and Selective Serotonin Reuptake Inhibitor or Selective Norepinephrine Reuptake Inhibitor Antidepressants With Serotonin Syndrome.

Importance: In 2006, the US Food and Drug Administration (FDA) issued an advisory warning on the risk of serotonin syndrome with concomitant use of triptans and selective serotonin reuptake inhibitor (SSRI) or selective norepinephrine reuptake inhibitor (SNRI) antidepressants, but the true risk of serotonin syndrome in these patients remains unknown. Objective: To assess the risk of serotonin syndrome with concomitant use of triptans and SSRI or SNRI antidepressants. Design, Setting, and Participants: This study used electronic health record data from the Partners Research Data Registry (RPDR) to identify patients who had received an International Classification of Diseases, Ninth Revision diagnosis compatible with serotonin syndrome who had been coprescribed triptans and SSRI or SNRI antidepressants in the Greater Boston, Massachusetts, area from January 1, 2001, through December 31, 2014 (14 years). Clinical information was extracted to determine whether the case met formal diagnostic criteria and had coprescription within a calendar year. Both conservative and broad case definitions were used to better characterize the spectrum of risk. Data analysis was performed from November 23, 2016, to July 15, 2017. Main Outcomes and Measures: Incidence of serotonin syndrome. Results: The RPDR search revealed 47 968 (±3) unique patients who were prescribed triptans during the 14-year period of the study. A total of 19 017 (±3) patients were coprescribed triptans and antidepressants during the study, with a total of 30 928 person-years of exposure. Serotonin syndrome was suspected in 17 patients. Only 2 patients were classified as having definite serotonin syndrome (incidence rate, 0.6 cases per 10 000 person-years of exposure; 95% CI, 0.0-1.5). Five patients were classified as having possible serotonin syndrome (incidence rate with these 5 cases added to the 2 definite cases, 2.3 cases per 10 000 person-years of exposure; 95% CI, 0.6-3.9). The proportion of patients with triptan prescriptions who were coprescribed an SSRI or SNRI antidepressant was relatively stable during the study, ranging from 21% to 29%. Conclusions and Relevance: The risk of serotonin syndrome associated with concomitant use of triptans and SSRIs or SNRIs was low. Coprescription of these drugs is common and did not decrease after the 2006 FDA advisory. Our results cast doubt on the validity of the FDA advisory and suggest that it should be reconsidered.

Epidemiology and Economic Burden of Serotonin Syndrome With Concomitant Use of Serotonergic Agents: A Retrospective Study Utilizing Two Large US Claims Databases.

OBJECTIVE: Serotonin syndrome (SS) is an adverse drug reaction occurring among patients receiving serotonergic agents (SAs), and although SAs are commonly prescribed, the epidemiology and economic burden of SS with concomitant SA use have not been comprehensively examined. The objective of this study was to investigate the prevalence, incidence, and economic burden of SS with SA use. METHODS: A retrospective cohort study was conducted using Veterans Health Administration (VHA) records (identification period: October 1, 2008-September 30, 2012) and commercially insured patient records (Intercontinental Marketing Services PharMetrics Plus; identification period: January 1, 2010-December 31, 2013). Cohorts were based on drug classification and exposure: single monoamine oxidase inhibitor (MAOI), MAOIs in combination with SAs, single non-MAOI SA, and multiple non-MAOI SAs (2, 3, 4, ≥ 5). Participants were aged ≥ 18 years with continuous health plan enrollment for 12 months prior to the first SA claim. Outcomes were SS events (ICD-9-CM: 333.99), annual incidence and prevalence, related health care utilization and costs, and SS incidence relative risk. RESULTS: Over 15 million patients were identified and categorized by SA prescription type. SS incidence in both populations decreased: 0.19%-0.07% (VHA) and 0.17%-0.09% (commercially insured). Overall SS prevalence decreased during the study period. Compared to single non-MAOI SA patients, SS incidence relative risk was highest among patients prescribed ≥ 5 non-MAOI SAs. Inpatient stays accounted for 4.35% (VHA) and 0.88% (commercially insured) of all SS events. Of SS-related inpatient stays, median costs were $8,765 (VHA) and $10,792 (commercially insured). CONCLUSIONS: SS incidence and prevalence and SS-related hospitalization risk among patients prescribed SAs were low in both populations. This study provides additional information regarding SS risk associated with SA use.

Incidence of Serotonin Syndrome With Combined Use of Linezolid and Serotonin Reuptake Inhibitors Compared With Linezolid Monotherapy.

PURPOSE: Linezolid is a monoamine oxidase inhibitor that may increase the risk of serotonin syndrome in patients receiving combination selective serotonin reuptake inhibitors (SSRIs) or serotonin norepinephrine reuptake inhibitors (SNRIs). The objective of this study was to compare the incidence of serotonin syndrome when linezolid was administered alone and in combination with SSRIs or SNRIs. METHODS: This was a retrospective case-control study of adult inpatients admitted to the University of Iowa Hospitals and Clinics who received linezolid between January 2010 and December 2014. Patients who received linezolid with or within 14 days of an SSRI or SNRI were eligible for inclusion in the combination therapy group. Patients who received linezolid alone were matched by age and gender to patients in the combination therapy group, and 3 monotherapy patients were included for each combination therapy patient. Clinical features consistent with serotonin syndrome were assessed using the Sternbach and Hunter criteria. RESULTS: A total of 348 patients were included in this study, of which 87 received combination therapy and 261 received linezolid monotherapy. One patient given combination therapy (1.1%) and 1 patient given linezolid monotherapy (0.4%) were determined to have a diagnosis of serotonin syndrome (P = 0.438; relative risk, 3.00; 95% confidence interval, 0.19-47.45). In both cases, signs and symptoms of serotonin syndrome reversed upon discontinuation of linezolid therapy. CONCLUSIONS: There was no significant difference in the incidence of serotonin syndrome when linezolid was used alone or in combination with an SSRI or SNRI, and the overall incidence of serotonin syndrome was low.

Acute Presentation of Nonmotor Symptoms in Parkinson's Disease.

There are a few syndromes involving the nonmotor symptoms of Parkinson's disease and other movement disorders that can quickly lead to severe morbidity and mortality, and, as such, need rapid identification and management. Among these are neuroleptic malignant syndrome, serotonin syndrome, dopamine agonist withdrawal syndrome, and dystonic storm. It is important to maintain a high index of suspicion for these disorders as lack of identification can lead to death. Many of these acutely occurring nonmotor syndromes are primarily the result of imbalances in dopaminergic and serotonergic systems due to changes in pharmacologic management of psychiatric disorders or Parkinson's disease. We discuss these acutely occurring nonmotor symptoms in order to raise awareness and also to highlight how these extremes in symptoms may uniquely shed light on the pathophysiology of Parkinson's disease.