Serotonin syndrome after lithium add-on medication to paroxetine

Is Poor Lithium Response in Individuals with Bipolar Disorder Associated with Increased Degradation of Tryptophan along the Kynurenine Pathway? Results of an Exploratory Study

Bipolar disorder is associated with an inflammation-triggered elevated catabolism of tryptophan to the kynurenine pathway, which impacts psychiatric symptoms and outcomes. The data indicate that lithium exerts anti-inflammatory effects by inhibiting indoleamine-2,3-dioxygenase (IDO)-1 activity. This exploratory study aimed to investigate the tryptophan catabolism in individuals with bipolar disorder (n = 48) compared to healthy controls (n = 48), and the associations with the response to mood stabilizers such as lithium, valproate, or lamotrigine rated with the Retrospective Assessment of the Lithium Response Phenotype Scale (or the Alda scale). The results demonstrate an association of a poorer response to lithium with higher levels of kynurenine, kynurenine/tryptophan ratio as a proxy for IDO-1 activity, as well as quinolinic acid, which, overall, indicates a pro-inflammatory state with a higher degradation of tryptophan towards the neurotoxic branch. The treatment response to valproate and lamotrigine was not associated with the levels of the tryptophan metabolites. These findings support the anti-inflammatory properties of lithium. Furthermore, since quinolinic acid has neurotoxic features via the glutamatergic pathway, they also strengthen the assumption that the clinical drug response might be associated with biochemical processes. The relationship between the lithium response and the measurements of the tryptophan to the kynurenine pathway is of clinical relevance and may potentially bring advantages towards a personalized medicine approach to bipolar disorder that allows for the selection of the most effective mood-stabilizing drug.

Lithium inhibits tryptophan catabolism via the inflammation-induced kynurenine pathway in human microglia

Despite its decades' long therapeutic use in psychiatry, the biological mechanisms underlying lithium's mood-stabilizing effects have remained largely elusive. Here, we investigated the effect of lithium on tryptophan breakdown via the kynurenine pathway using immortalized human microglia cells, primary human microglia isolated from surgical specimens, and microglia-like cells differentiated from human induced pluripotent stem cells. Interferon (IFN)-γ, but not lipopolysaccharide, was able to activate immortalized human microglia, inducing a robust increase in indoleamine-2,3-dioxygenase (IDO1) mRNA transcription, IDO1 protein expression, and activity. Further, chromatin immunoprecipitation verified enriched binding of both STAT1 and STAT3 to the IDO1 promoter. Lithium counteracted these effects, increasing inhibitory GSK3β^S9 phosphorylation and reducing STAT1^S727 and STAT3^Y705 phosphorylation levels in IFN-γ treated cells. Studies in primary human microglia and hiPSC-derived microglia confirmed the anti-inflammatory effects of lithium, highlighting that IDO activity is reduced by GSK3 inhibitor SB-216763 and STAT inhibitor nifuroxazide via downregulation of P-STAT1^S727 and P-STAT3^Y705 . Primary human microglia differed from immortalized human microglia and hiPSC derived microglia-like cells in their strong sensitivity to LPS, resulting in robust upregulation of IDO1 and anti-inflammatory cytokine IL-10. While lithium again decreased IDO1 activity in primary cells, it further increased release of IL-10 in response to LPS. Taken together, our study demonstrates that lithium inhibits the inflammatory kynurenine pathway in the microglia compartment of the human brain.

Serotonin syndrome

Aims and method

To define serotonin syndrome and its symptoms and to discover which drugs or drug combinations are likely to cause it. A review of literature (including case reports) relating to serotonin syndrome collated from searches of MedLine and Micromedex covering the period January 1991 to July 1998.

Results

Most of the data found were either individual case reports or reviews of case reports. Reports of serotonin syndrome seem to be growing, certainly since the introduction of selective serotonin reuptake inhibitors. Particular combinations seem most likely to induce serotonin syndrome. Awareness of this syndrome as a distinct clinical entity seems to be growing.

Clinical implications

Serotonin syndrome is more likely to occur with drug combinations, especially those involving monoamine oxidase inhibitors. It can also occur when swapping antidepressant therapy, especially If changing from a long acting antidepressant such as fluoxetine. Caution is needed when changing antidepressants and particularly when they are used in combination.

Drug Interactions with Lithium: An Update

Lithium has been used for the management of psychiatric illnesses for over 50 years and it continues to be regarded as a first-line agent for the treatment and prevention of bipolar disorder. Lithium possesses a narrow therapeutic index and comparatively minor alterations in plasma concentrations can have significant clinical sequelae. Several drug classes have been implicated in the development of lithium toxicity over the years, including diuretics and non-steroidal anti-inflammatory compounds, but much of the anecdotal and experimental evidence supporting these interactions is dated, and many newer medications and medication classes have been introduced during the intervening years. This review is intended to provide an update on the accumulated evidence documenting potential interactions with lithium, with a focus on pharmacokinetic insights gained within the last two decades. The clinical relevance and ramifications of these interactions are discussed.

Serotonin syndrome in patients with headache disorders

Serotonin syndrome (SS) is an iatrogenic, drug-induced syndrome caused by serotoninergic agent. Various serotonergic drugs are used in different headache disorders. Therefore, a possibility of developing SS exists in patients with headache. Herein, we are reporting two patients with headache disorders who developed SS.Case 1: a 49-year-old man had a 6-year history of episodic cluster headache (CH). However, he had never been diagnosed with CH before reporting to us. He had been receiving amitriptyline, tramadol/acetaminophen combination and flunarizine. Lithium was started for CH. He developed features consistent with SS. The patient responded to cyprohepatdine.Case 2: a 36-year-old chronic migraineur was on amitriptyline. Addition of sodium valproate led to the development of new features that fulfilled the criteria of SS. The patient responded to cyprohepatdine.As SS may be fatal, there is a need to increase awareness about SS in physicians treating patients with headache.

General pharmacokinetic/pharmacodynamic concepts of mood stabilizers in the treatment of bipolar disorder

Introduction:

Mood stabilizers are the recommended treatment for patients who receive a diagnosis of bipolar disorder. Because of the necessity of mood stabilizer treatment in patients with bipolar disorder and the extent of pharmacokinetic and pharmacodynamic principles involved, the purpose of this review is to summarize the pharmacokinetic principles of lithium in addition to the pharmacodynamics of lithium, carbamazepine, lamotrigine, and valproic acid/valproate.

Methods:

Practice guidelines, review articles, and clinical trials were located using online databases PubMed, CINAHL, IDIS, and Medline. Search terms included at least one of the following: bipolar disorder, carbamazepine, lamotrigine, lithium, mood stabilizers, pharmacokinetics, pharmacodynamics, valproate, and valproic acid. Online clinical databases Dynamed® and Lexicomp® were also used in the study.

Results:

Mood stabilizers collectively possess distinct qualities that are closely regarded before, during, and after therapeutic initiation. Individual patient characteristics, coupled with these observed traits, add to the complexity of selecting the most optimal neurologic agent. Each medication discussed uniquely contributes to both the maintenance and restoration of overall patient well-being.

Discussion:

Introduction of mood stabilizers into drug regimens is often done in the presence of an array of mitigating factors. Safety and efficacy measures are commonly used to gauge desired results. Careful monitoring of patients' responses to selected therapies is paramount for arriving at appropriate clinical outcomes.

Mood stabilizers for patients with bipolar disorder: the state of the art

Bipolar disorder (BD) is a prevalent and disabling condition, often comorbid with other medical and psychiatric conditions and frequently misdiagnosed. International treatment guidelines for BD recommend the use of mood stabilizers - either in monotherapy or in association - as the gold standard in both acute and long-term therapy. Commonly used in the clinical practice of BD, mood stabilizers have represented an evolving field over the last few years. The concept of stabilization, in fact, has been stressed as the ultimate objective of the treatment of BD, given the chronic and recurrent nature of the illness, which accounts for its significant levels of impairment and disability. To date, different compounds are included within the broad class of mood stabilizers, with lithium, anticonvulsants and, more recently, atypical antipsychotics being the most representative agents. This article is aimed at providing an updated review of the available literature in relation to the role of mood stabilizers in BD, with particular emphasis on their mechanism of action, main clinical aspects and specific use in the different phases of BD treatment, according to the most recently published international treatment guidelines.

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.

Tolerability of combined treatment with lithium and paroxetine in patients with bipolar disorder and depression

Patients with bipolar disorder are often prescribed lithium in combination with a selective serotonin reuptake inhibitor. Doubts still remain, however, about the safety of the combination, particularly with regard to the risk of developing a serotonin syndrome. The authors retrospectively evaluated the safety of the combination of lithium and paroxetine when the two medications were sequentially prescribed in patients with bipolar disorder. The authors examined a sample of 17 patients with bipolar disorder who were treated with lithium during a depressive episode and who required paroxetine as an adjunctive antidepressant to ongoing lithium treatment. Averaging across all subjects, no statistically significant increase was found for any of the somatic symptoms that were assessed before and after paroxetine was added to ongoing lithium therapy. Examining the clinical records of each patient in detail; however, four patients who developed significant adverse events, possibly related to an emerging serotonin syndrome were identified. Clinicians should be aware of the possible development of a serotonin syndrome among patients in whom paroxetine is added to ongoing lithium treatment.

Changes in quantitatively assessed tremor during treatment of major depression with lithium augmented by paroxetine or amitriptyline

Tremor is a relatively frequent side effect of lithium and of antidepressants with serotonergic properties. It can be expected that combinations of lithium (which is itself serotonergic) with such antidepressants will enhance not only efficacy, but also the incidence of side effects, including tremor. To quantitatively monitor the effect of antidepressant augmentation of ongoing lithium therapy on tremor, lithium-maintained patients with a breakthrough episode of major depression were randomly assigned under double-blind conditions to receive paroxetine 20 mg/day (N = 14) or amitriptyline 75 mg/day (N = 17). The initial dosages could be increased after 2 weeks to 40 mg/day and 150 mg/day, respectively, and the patients were treated for 6 weeks. Tremor activity was assessed weekly, quantitatively by accelerometry and qualitatively with the Dosage Record and Treatment Emergent Symptom Scale. Statistical analysis detected no significant difference between the treatment groups with respect to changes in mean tremor activity relative to baseline. However, analysis of the pooled data showed that tremor increased significantly during the course of combined lithium and antidepressant therapy, with the greatest increments occurring independent of dosage approximately 3 weeks after initiation of combination treatment. Although the mean tremor activity subsided toward the end of treatment, tremor activity on the whole was still significantly greater after 6 weeks of combined lithium and antidepressant treatment than at the start of combination therapy. Increased tremor was not associated with decreased medication compliance, and no patient discontinued treatment because of increased tremor. Tremor frequency was not affected by the study treatments.

A second trial of clozapine in a case of granulocytopenia

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

Serotonin syndrome: history and risk

This review focuses on the history of investigations into the behavioural reaction resulting from excess stimulation of post-synaptic 5-hydroxytryptamine receptors and the relative risk of this occurring with different combinations of drugs. Other aspects, particularly treatment with 5-hydroxytryptamine receptor antagonists, are reviewed in a recent separate paper [44]. The first human case was in 1955 and animal work had defined the characteristic features by 1958, and established they were lessened by chlorpromazine. Substantial evidence of a 'dose-effect' relationship existed by 1984. The relative risk with different drug combinations is assessed from available evidence and argued to be strongly associated with the degree of elevation of 5-hydroxytryptamine, which is greatest following combinations of irreversible inhibitors of monoamine oxidase A and B with potent serotonin reuptake inhibitors. The various serotonergic drugs that may be implicated in serotonin syndrome are tabulated and discussed in relation to the relative risk. It is suggested that the proposed 'diagnostic criteria' for serotonin syndrome are inappropriate since there is a continuous spectrum from side effects to toxicity. The term 'serotonin syndrome' may encourage the presumption that it is an idiosyncratic response, as neuroleptic malignant syndrome is usually considered to be. The terms 'toxic serotomimetic reaction' or 'toxic serotonin syndrome' may be preferable alternatives. The differences between serotonin syndrome and neuroleptic malignant syndrome are highlighted with examples from difficult or questionable cases in the recent literature. It is proposed that more systematic national collection of toxicity data is essential in order to quantify the relative risk of serotonin syndrome with various combinations of serotonergic drugs.

Serotonergic synergism: the risks and benefits of combining the selective serotonin reuptake inhibitors with other serotonergic drugs

It has become common clinical practice to combine the selective serotonin reuptake inhibitors with other serotonergic agents for augmentation or adjunctive purposes. The empirical basis for using these combinations remains limited, but is growing. Also growing is a literature that suggests that even the most apparently benign combinations of serotonergic drugs carry at least some risk of serious pharmacokinetic or pharmacodynamic drug interactions, such as a serotonin syndrome.