Serotonin toxicity: a short review of the literature and two case reports involving citalopram

Antidepressant and antiobesity drug-induced serotonin syndrome complicated by multiple organ injury: A case report

RATIONALE

Serotonin syndrome (SS), also referred to as serotonin toxicity, is a potentially life-threatening condition associated with increased serotonergic activity in the central nervous system, but often underdiagnosed due to its variable presentation.

PATIENT CONCERNS

A 46-year-old woman presented to the emergency department with complaints of fever, confused mental status with slurred speech, agitation. The patient also exhibited lower extremities weakness with spontaneous clonus. The physical examination revealed tachycardia and tachypnea. The patient was taking fluoxetine for depression disorder and anti-obesity medications including topiramate and phentermine. Initial laboratory finding demonstrated severe hypoxemia and rhabdomyolysis with renal dysfunction.

DIAGNOSES

Spinal tap and brain magnetic resonance imaging showed no clues that could explain the patient's neuromuscular symptoms. Based on the patient's overall presentation and use of medications, a diagnosis of SS was made. However, the patient's inpatient treatment was complicated by pulmonary thromboembolism (PTE) and stress-induced cardiomyopathy (SCM).

INTERVENTIONS

The patient was intubated and admitted to the intensive care unit for supportive care, including mechanical ventilation and hemodialysis. The patient received an intravenous benzodiazepine and vecuronium for controlling autonomic dysfunction and neuromuscular symptoms. Anticoagulation was also initiated promptly following the diagnosis of PTE.

OUTCOMES

After intensive supportive care, she was discharged 1 month after admission with normalized left ventricular motion and systolic function.

LESSONS

This case highlights that SS should be considered as an etiology of unexplained episodes of altered mental status and neuromuscular abnormalities. Rarely, this condition can be complicated by multiple organ injury, involving conditions such as rhabdomyolysis, renal failure, SCM and PTE. Thus, physicians must be aware of the various and atypical manifestations of serotonin syndrome in order to avoid missing the diagnosis of a potentially fatal condition.

Drug-Drug Interactions of Selective Serotonin Reuptake Inhibitors: A Pharmacovigilance Study on Real-World Evidence from the EudraVigilance Database

As the most common psychiatric symptom, depression represents a subject of high interest for the medical community. Background/Objectives: International guidelines consider selective serotonin reuptake inhibitors (SSRIs) the first-line treatment of depression. Although having better efficacy and tolerability in comparison to tricyclic antidepressants or monoamine oxidase inhibitors, the diversity and potential severity of adverse effects and interactions manifested by SSRIs, combined with the frequency of prescriptions, lead to the necessity of evaluating real-world data. The aim of this study was to identify and evaluate the drug interactions reported in EudraVigilance (EV) for the six SSRIs representatives that are authorized in Europe: fluoxetine (FXT), fluvoxamine (FVM), citalopram (CIT), escitalopram (ESC), paroxetine (PAR) and sertraline (SER). The entire class of SSRIs was examined as a comparator to identify whether one of the representatives was more prone to reporting. Methods: Descriptive analysis and disproportionality analysis were conducted on data extracted from the EV database. Results: A total of 326,450 adverse reactions (ADRs) were reported for the SSRIs group. Approximately a quarter of these (n = 83,201; 25.46%) were reported for SER and 22.37% (n = 73,131) for PAR. Of the total ADRs reported, 2.12% (n = 6925) represent preferred terms related to drug-drug interactions (DDIs): SER (n = 1474; 22.37%), CIT (n = 1272, 19.86), and FXT (n = 1309, 19.83%). Specific ADRs related to inhibitory activity represent 0.98%, and for potentiating activity, 1.89%. Conclusions: Although representing a small value of the total ADRs, DDIs may be related to severe outcomes. Awareness should be raised for this category of ADRs that can be reduced by the joined efforts of physicians and pharmacists.

Antiepileptic drugs and serotonin syndrome- A systematic review of case series and case reports

Serotonin syndrome (SS) is a drug‑induced, potentially fatal, clinical syndrome resulting from drugs that have serotonergic properties. Several antiepileptic drugs (AEDs) are known to have serotonergic properties and it can be hypothesized that such AEDs can cause SS. This study aims to review the literature on SS in patients receiving AEDs. We performed a systematic review of Scopus and MEDLINE/PUBMED for case reports and case series of SS where patients had received at least one AED at the onset of symptoms. The cases published in the English literature between 1 January 1991 and 1 April 2021 were included. Initial search identified 1263 articles of which 63 (76 patients) were included in the final analysis. Most of the included cases (53 cases, 70%) have been published in the last 10 years. The mean age of the 76 patients was 40.6 ± 17.8 years, and 51% of cases were females. These patients had been exposed to a total of 8 different types of AEDs. Valproic acid was the most common drug (29, 38%), followed by lamotrigine (22, 29%), gabapentin (16, 21%), pregabalin (seven, 9%), topiramate (five, 7%) and carbamazepine (two, 3%). There has been one case each with phenytoin and oxcarbazepine. Seven (9%) patients received more than one AEDs. Most patients (67, 88%) also received other serotoninergic agents. Only nine (12%) patients were on AEDs alone. The most common clinical condition for using AEDs was psychiatric disorders (36 patients, 47.3%), followed by migraine (17, 22.4%), other painful conditions (15, 19.7%), epilepsy (7, 9.2%), and perioperative conditions (8, 10.5%). Death was reported in two patients. We suggest that AEDs, because of their serotonergic properties, may induce SS, especially in patients who are on another serotonergic agent.

MDMA to Treat PTSD in Adults

Post-traumatic stress disorder (PTSD) has become one of the most common psychiatric diagnosis in the United States specifically within the veteran population. The current treatment options for this debilitating diagnosis include trauma-focused psychotherapies along with selective serotonin reuptake inhibitors (SSRI) and serotonin-norepinephrine reuptake inhibitors (SNRI).¹ MDMA has recently been shown as a novel therapeutic agent with promisingly results in the treatment of PTSD. MDMA is a psychoactive compound traditionally categorized as a psychedelic amphetamine that deemed a Schedule I controlled substance in the 1980s. Prior to its status as a controlled substance, it was used by psychotherapists for an array of psychiatric issues. In more recent times, MDMA has resurfaced as a potential therapy for PTSD and the data produced from randomized, controlled trials back the desire for MDMA to be utilized as an effective pharmacologic therapy in conjunction with psychotherapy.².

Management of severe arterial hypertension associated with serotonin syndrome: a case report analysis based on systematic review techniques

Serotonin syndrome is thought to arise from serotonin excess. In many cases, symptoms are mild and self-limiting. But serotonin syndrome can become life threatening, when neuromuscular hyperexcitability spins out of control. Uncontainable neuromuscular hyperexcitability may lead to cardiovascular complications, linked to extreme changes in blood pressure. Currently, there is little guidance on how to control blood pressure in hyperserotonergic states. We report a case with treatment-resistant arterial hypertension, followed by a clinical review (using systematic review principles and techniques) of the available evidence from case reports published between 2004 and 2016 to identify measures to control arterial hypertension associated with serotonin syndrome. We conclude that classic antihypertensives may not be effective for the treatment of severe hypertension associated with serotonin syndrome. Benzodiazepines may lower blood pressure. Patients with severe hypertension not responding to benzodiazepines may benefit from cyproheptadine, propofol or both. In severe cases, higher cyproheptadine doses than currently recommended may be necessary.

Fatal intoxication with antidepressants: a case with many culprits

Serotonin-specific reuptake inhibitors (SSRIs) are generally considered safe drugs but fatal adverse effects do sometimes occur, often as a consequence of interactions with other serotonin active drugs. Polypharmacy is usually a problem that the elderly encounter, but it can also have dire consequences for young people, especially when an underlying heart condition is present. Thus, failure to diagnose heart disease and the use of contraindicated medications can be a lethal combination, irrespective of age. Here we present a case of a young adult suffering from bipolar disorder who used a combination of two SSRIs (citalopram and fluoxetine) and a monoamine oxidase inhibitor (MAO; moclobemide) with tragic consequences. The deceased also suffered from undiagnosed hypertrophic cardiomyopathy and was carrier of a genotype that may have predisposed him to increased sensitivity to SSRIs. The apparent difficulty in establishing the manner of death in this case is also discussed.

Case Reports Describing Amantadine Intoxication in a Rehabilitation Hospital

BACKGROUND

Amantadine is widely used to improve reduced spontaneity and prevent aspiration pneumonia. There are few reports on cases of amantadine intoxication in the field of rehabilitation.

CASES

Case 1 involved an 83-year-old man with a history of a lacunar infarction who was transferred to our rehabilitation hospital after a left femoral neck fracture and a left upper arm fracture. He had mild renal dysfunction. Although he was started on oral amantadine 150 mg/dayto reverse a decline in spontaneity, he could not begin rehabilitation therapy because of hallucinations and myoclonus. Furthermore, he developed aspiration pneumonia as a result of a consciousness disorder. After stopping amantadine, his toxic symptoms disappeared completely. Case 2 involved a 53-year-old man who was transferred to our hospital for rehabilitation after a brain contusion. He was started on oral amantadine 100 mg/day to reverse a decline in spontaneity. After amantadine was increased to 150 mg/day, myoclonus and hallucinations developed. At that time, his renal function was mildly impaired. The concentration of amantadine in his blood serum was found to be 4783 ng/dl. After amantadine was stopped, his spontaneity decline recurred. After restarting amantadine at 50 mg/day, his toxic symptoms did not reappear, and the decline in his spontaneity improved.

DISCUSSION

Amantadine is a renally excreted drug that may cause toxic symptoms as a result of decreased renal function. It is necessary to monitor renal function and toxic symptoms when amantadine is administered in rehabilitation hospitals.

Potential drug-drug interactions among prescriptionsfor elderly patients in primary health care

BACKGROUND/AIM

Elderly patients are at high risk from drug-drug interactions (DDIs). This study evaluates the potential DDIs in Turkish elderly patients at a primary health care outpatient clinic.

MATERIALS AND METHODS

Online database systems were used to examine DDIs on the prescriptions of patients (n = 1206). The clinical severity of DDIs was classified by the Lexi-Interact Online database.

RESULTS

Of the 5059 prescriptions, 33% were found to have DDIs. We detected 29 (0.9%) A, 380 (11.8%) B, 2494 (77.7%) C, 289 (9%) D, and 18 (0.6%) X risk rating category DDIs among the prescriptions. Prescriptions of female patients and patients aged between 65 and 72 years showed significantly higher number of DDIs. The frequency of DDIs increased both with the number of drugs and combined preparations per prescription. Acetylsalicylic acid and salbutamol were the most frequently prescribed drugs contributing to clinically important DDIs. Additionally, acetylsalicylic acid and escitalopram, which interact with each other, were found on the list of Beers criteria. The most predicted clinical outcomes of DDIs were increase in therapeutic efficacy and adverse/toxic reactions. Conclusions: Prediction of DDIs in elderly patients will provide better prescribing and drug safety. Use of nonsteroidal anti-inflammatory agents, selective serotonin reuptake inhibitors, and beta-2 adrenergic receptor agonists should be closely monitored.

Effect of CYP2D6 genetic polymorphism on the metabolism of citalopram in vitro

Genetic polymorphisms of CYP2D6 significantly influence the efficacy and safety of some drugs, which might cause adverse effects and therapeutic failure. We aimed at investigating the role of CYP2D6 in the metabolism of citalopram and identifying the effect of 24 CYP2D6 allelic variants we found in Chinese Han population on the metabolism of citalopram in vitro. These CYP2D6 variants expressed by insect cells system were incubated with 10-1000 μM citalopram for 30 min at 37 °C and the reaction was terminated by cooling to -80 °C immediately. Citalopram and its metabolites were analyzed by high-performance liquid chromatography (HPLC). The intrinsic clearance (Vmax/Km) values of the variants toward citalopram metabolites were significantly altered, 38-129% for demethylcitalopram and 13-138% for citalopram N-oxide when compared with CYP2D6*1. Most of the tested rare alleles exhibited significantly decreased values due to increased Km and/or decreased Vmax values. We conclude that recombinant system could be used to investigate the enzymes involved in drug metabolism and these findings suggest that more attention should be paid to subjects carrying these CYP2D6 alleles when administering citalopram in the clinic.

Safety and tolerability of antidepressant co-treatment in acute major depressive disorder: results from a systematic review and exploratory meta-analysis

INTRODUCTION

Although antidepressant (AD) monotherapy is recommended first-line for major depressive disorder (MDD), AD + AD co-treatment is common.

AREAS COVERED

We conducted the first systematic review searching PubMed/MEDLINE/PsycInfo/Embase from database inception until 1 June 2015 for acute randomized trials in ≥ 20 adults with MDD comparing AD monotherapy with AD + AD co-treatment that reported quantitative data on adverse events (AEs). Meta-analyzing 23 studies (n = 2435, duration = 6.6 weeks) AD monotherapy and AD + AD co-treatment were similar regarding intolerability-related discontinuation (risk ratio [RR] = 1.38, 95% CI = 0.89 - 1.10) and frequency of ≥ 1 AE (RR = 1.19, 95% CI = 0.95 - 1.49). Nevertheless, AD + AD co-treatment was associated with significantly greater burden regarding 4/25 AEs (tremor: RR = 1.55, 95% CI = 1.01 - 2.38; sweating: RR = 1.95, 95% CI = 1.13 -3.38, ≥ 7% weight gain: RR = 3.15, 95% CI = 1.34 - 7.41; weight gain = 2.17, 95% CI = 0.71 - 3.63 kg), but not more CNS, gastrointestinal, sexual or alertness-related AEs. However, 11/25 AEs (44.0%) were reported in only 1 - 2 studies. Adding noradrenergic and specific serotonergic antidepressants (NaSSA) or tricyclic antidepressants (TCA) to selective serotonin reuptake inhibitors (SSRIs) was specifically associated with more AEs.

EXPERT OPINION

The potential for increased AEs with AD + AD co-treatment needs to be considered vis-à-vis unclear efficacy benefits of this strategy. In particular, NaSSAs and TCAs should be added to SSRIs with caution. Clearly, more data on side-effect burden of AD + AD co-treatment are needed.

Spasticity in multiple sclerosis and role of glatiramer acetate treatment

INTRODUCTION

Spasticity is one of the most disabling and difficult-to-treat symptoms shown by patients with multiple sclerosis, who often show a suboptimal and unsatisfactory response to classic treatment and new available nonpharmacological alternatives. Due to the progressive nature of this condition, the early management should be essential to improve long-term outcomes.

METHODS

We performed a narrative literature review of the contribution of spasticity to the burden of multiple sclerosis and the potential role of classic disease-modifying drugs.

RESULTS

Added to the underlying pathophysiology of spasticity, certain external factors and drugs such as interferon may exacerbate the existing condition, hence their awareness is crucial as part of an effective management of spasticity. Furthermore, the evidence for the effectiveness of glatiramer acetate in preventing spasticity in naïve patients and in those switching from interferon should not be ignored.

CONCLUSIONS

This literature review proposes the examination of spasticity and the influence of classic disease-modifying agents on the level of existing condition among the variables to be considered when deciding on therapy for multiple sclerosis in clinical practice.

[Drug interactions in pain therapy]

BACKGROUND

Pain is one of the most common reasons for consulting a physician. Chronic pain patients often suffer from a variety of comorbidities, such as depression and anxiety and they are therefore often simultaneously treated with more than one drug. The probability of drug interactions increases with every additional drug.

MATERIAL AND METHODS

A systematic internet and literature search up to February 2015 was carried out. Systematic lists were included. In addition, the drug prescription information sheets were used and an internet search via Pubmed and google.com was carried out for drugs alone and in combination in order to find substance-specific interactions.

RESULTS

A differentiation is made between pharmaceutical, pharmacodynamic and pharmacokinetic drug interactions. Pharmaceutical interactions are caused by chemical, physical or physicochemical incompatibility of drugs or adjuvants used. These can even occur outside the body and during concomitant administration via the same route. A pharmacodynamic interaction in pain management is for example the additive sedative effect of opioids and benzodiazepines when taken together. Pharmacokinetic interactions occur during the absorption, distribution, metabolism and in the elimination phases.

CONCLUSION

Many drug interactions can be avoided by careful and continuous evaluation of pharmacotherapy and if necessary its adaptation; however, a sound knowledge of the underlying pharmacological mechanisms and the properties of currently used analgesics is necessary.

Myoclonus in renal failure: Two cases of gabapentin toxicity

Gabapentin, an AED approved for the adjunctive treatment of partial seizures with/without secondary generalization and for the treatment of postherpetic neuralgia, is frequently used off-label for the treatment of both psychiatric and pain disorders. Since gabapentin is cleared solely by renal excretion, dosing requires consideration of the patient's renal function. Myoclonic activity may occur as a complication of gabapentin toxicity, especially with acute kidney injury or end-stage renal disease. We report 2 cases of myoclonic activity associated with gabapentin toxicity in the setting of renal disease which resolved with discontinuation of gabapentin and treatment with hemodialysis and peritoneal dialysis. As gabapentin has multiple indications and off-label uses, an understanding of myoclonus, neurotoxicity, and renal dosing is important to clinicians in multiple specialties.

Neurotranmission systems as targets for toxicants: a review

Neurotransmitters are chemicals that transmit impulses from one nerve to another or from nerves to effector organs. Numerous neurotransmitters have been described in mammals, amongst them acetylcholine, amino acids, amines, peptides and gases. Toxicants may interact with various parts of neurotransmission systems, including synthetic and degradative enzymes, presynaptic vesicles and the specialized receptors that characterize neurotransmission systems. Important toxicants acting on the cholinergic system include the anticholinesterases (organophosphates and carbamates) and substances that act on receptors such as nicotine and the neonicotinoid insecticides, including imidacloprid. An important substance acting on the glutamatergic system is domoic acid, responsible for amnesic shellfish poisoning. 4-Aminobutyric acid (GABA) and glycine are inhibitory neurotransmitters and their antagonists, fipronil (an insecticide) and strychnine respectively, are excitatory. Abnormalities of dopamine neurotransmission occur in Parkinson's disease, and a number of substances that interfere with this system produce Parkinsonian symptoms and clinical signs, including notably 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is the precursor of 1-methyl-4-phenylpyridinium. Fewer substances are known that interfere with adrenergic, histaminergic or seroninergic neurotransmission, but there are some examples. Among peptide neurotransmission systems, agonists of opioids are the only well-known toxic compounds.

Pharmacological potential of biogenic amine-polyamine interactions beyond neurotransmission

Histamine, serotonin and dopamine are biogenic amines involved in intercellular communication with multiple effects on human pathophysiology. They are products of two highly homologous enzymes, histidine decarboxylase and l-aromatic amino acid decarboxylase, and transmit their signals through different receptors and signal transduction mechanisms. Polyamines derived from ornithine (putrescine, spermidine and spermine) are mainly involved in intracellular effects related to cell proliferation and death mechanisms. This review summarizes structural and functional evidence for interactions between components of all these amine metabolic and signalling networks (decarboxylases, transporters, oxidases, receptors etc.) at cellular and tissue levels, distinct from nervous and neuroendocrine systems, where the crosstalk among these amine-related components can also have important pathophysiological consequences. The discussion highlights aspects that could help to predict and discuss the effects of intervention strategies.

Differentiating serotonin syndrome and neuroleptic malignant syndrome

Serotonin syndrome (SS) and neuroleptic malignant syndrome (NMS) are two rare, but serious adverse reactions associated with psychotropic medications. While the disorders may share certain features, there are differences in how they are managed and treated. This article reviews the risk factors, clinical presentation, and treatment of SS and NMS.