Fluoxetine-induced memory impairment in an adolescent

5-HT2A receptors are involved in cognitive but not antidepressant effects of fluoxetine

The prefrontal cortex (PFC) plays a crucial role in cognitive and affective functions. It contains a rich serotonergic (serotonin, 5-HT) innervation and a high density of 5-HT receptors. Endogenous 5-HT exerts robust actions on the activity of pyramidal neurons in medial PFC (mPFC) via excitatory 5-HT2A and inhibitory 5-HT1A receptors, suggesting the involvement of 5-HT neurotransmission in cortical functions. However, the underlying mechanisms must be elucidated. Here we examine the role of 5-HT2A receptors in the processing of emotional and cognitive signals evoked by increasing the 5-HT tone after acute blockade of the 5-HT transporter. Fluoxetine (5-20mg/kg i.p.) dose-dependently reduced the immobility time in the tail-suspension test in wild-type (WT) and 5-HT2Aknockout (KO2A) mice, with non-significant differences between genotypes. Fluoxetine (10mg/kg i.p.) significantly impaired mice performance in the novel object recognition test 24h post-administration in WT, but not in KO2A mice. The comparable effect of fluoxetine on extracellular 5-HT in the mPFC of both genotypes suggests that presynaptic differences are not accountable. In contrast, single unit recordings of mPFC putative pyramidal neurons showed that fluoxetine (1.8-7.2mg/kg i.v.) significantly increased neuronal discharge in KO2A but not in WT mice. This effect is possibly mediated by an altered excitatory/inhibitory balance in the PFC in KO2A mice. Overall, the present results suggest that 5-HT2A receptors play a detrimental role in long-term memory deficits mediated by an excess 5-HT in PFC.

Effects of fluoxetine on the amygdala and the hippocampus after administration of a single prolonged stress to male Wistar rates: In vivo proton magnetic resonance spectroscopy findings

Posttraumatic stress disorder (PTSD) is an anxiety- and memory-based disorder. The hippocampus and amygdala are key areas in mood regulation. Fluoxetine was found to improve the anxiety-related symptoms of PTSD patients. However, little work has directly examined the effects of fluoxetine on the hippocampus and the amygdala. In the present study, male Wistar rats received fluoxetine or vehicle after exposure to a single prolonged stress (SPS), an animal model of PTSD. In vivo proton magnetic resonance spectroscopy ((1)H-MRS) was performed -1, 1, 4, 7 and 14 days after SPS to examine the effects of fluoxetine on neurometabolite changes in amygdala, hippocampus and thalamus. SPS increased the N-acetylaspartate (NAA)/creatine (Cr) and choline moieties (Cho)/Cr ratios in the bilateral amygdala on day 4, decreased the NAA/Cr ratio in the left hippocampus on day 1, and increased both ratios in the right hippocampus on day 14. But no significant change was found in the thalamus. Fluoxetine treatment corrected the SPS increases in the NAA/Cr and Cho/Cr levels in the amygdala on day 4 and in the hippocampus on day 14, but it failed to normalise SPS-associated decreases in NAA/Cr levels in the left hippocampus on day 1. These results suggested that metabolic abnormalities in the amygdala and the hippocampus were involved in SPS, and different effects of fluoxetine in correcting SPS-induced neurometabolite changes among the three areas. These findings have implications for fluoxetine treatment in PTSD.

Pharmacotherapy of School Refusal

This paper reviews the role and indications for pharmacotherapy of children with school refusal. The psychopharmacological treatment of school refusal is based mainly on evidence of the effectiveness of certain drugs in the treatment of adult disorders. There is some evidence that tricyclic antidepressants and benzobiazepines may be specifically useful in the treatment of school refusal, but further research is warranted. Potentially serious side effects mean that drugs are best confined to cases where psychological treatments have not been effective or where drugs are used briefly as an adjunct to a broader psychological treatment plan. Drugs may also have a role in the specific treatment of comorbid conditions associated with school refusal. Any use of drugs should involve regular reviews to monitor response, compliance, and side effects.

Cognitive–Behavioural Treatment of Internalising Disorders in Youth

Cognitive-behavioural (CB) therapy for internalising disorders in youth is discussed from both a procedural and empirical standpoint. A theoretical overview of CB treatment is provided, and the unique difficulties faced in the identification and treatment of internalising disorders are considered. With reference to specific internalising disorders (i.e., anxiety and depression), the present paper considers the differential application of CB strategies and the efficacy of treatment procedures. Issues relevant to CB treatment, including (a) flexibility in application, (b) developmental considerations, (c) treatment methodology, and (d) transportability, are discussed.

Helminth infection alters mood and short-term memory as well as levels of neurotransmitters and cytokines in the mouse hippocampus

Helminthic infections are important causes of morbidity and mortality in many developing countries, where children bear the greatest health burden. The ability of parasites to cause behavioral changes in the host has been observed in a variety of host-parasite systems, including the Taenia crassiceps-mouse model. In murine cysticercosis, mice exhibit a disruption in the sexual, aggressive and avoidance predator behaviors.

OBJECTIVE

The present study was conducted to characterize short-term memory and depression-like behavior, as well as levels of neurotransmitters and cytokines in the hippocampus of cysticercotic male and female mice.

METHODS

Cytokines were detected by RT-PCR and neurotransmitters were quantified by HPLC.

RESULTS

Chronic cysticercosis infection induced a decrease in short-term memory in both male and female mice, having a more pronounced effect in females. Infected females showed a significant increase in forced swimming tests with a decrease in immobility. In contrast, male mice showed an increment in total activity and ambulation tests. Serotonin levels decreased by 30% in the hippocampus of infected females whereas noradrenaline levels significantly increased in infected males. The hippocampal expression of IL-4 increased in infected female mice, but decreased in infected male mice.

CONCLUSION

Our study suggests that intraperitoneal chronic infection with cysticerci in mice leads to persistent deficits in tasks dependent on the animal's hippocampal function. Our findings are a first approach to elucidating the role of the neuroimmune network in controlling short-term memory and mood in T. crassiceps-infected mice.

Neuropsychological functioning in young subjects with generalized anxiety disorder with and without pharmacotherapy

The purpose of this study was to investigate the neuropsychological functioning and the effect of antidepressant drug intake on cognitive performance in a group of relatively young generalized anxiety disorder (GAD) patients. Forty patients with a DSM-IV diagnosis of GAD and 31 healthy subjects participated in the study (Control group, CON). None of the selected subjects had comorbid depression. GAD subjects were divided into two different subgroups: 18 were taking antidepressants [GAD-pharmacotherapy (GAD-p group)] and 22 were treatment-naïve (GAD group). Each group was administered with a comprehensive neuropsychological battery to assess attention, memory and executive functions. Performance on executive and non-verbal memory tasks of both GAD groups was largely worse than the CON group. However, these deficits seem to be more marked in patients taking antidepressants, especially in the domains of attention, non-verbal memory and executive functions. The present study indicates that GAD is associated with cognitive impairments among young adults. However, the observed association of neuropsychological deficits and the use of pharmacotherapy suggest a possible effect of antidepressant treatment on attention, executive functioning and non-verbal memory.

Differential effects of fluoxetine and venlafaxine on memory recognition: possible mechanisms of action

Serotonin-specific reuptake inhibitors (SSRI) and serotonin-norepinephrine reuptake inhibitors (SNRI) are antidepressant drugs commonly used to treat a wide spectrum of mood disorders (Wong and Licinio, 2001). Although they have been clinically used for more than 50 years, the molecular and cellular basis for the action of SSRIs and SNRIs is not clear. Considering that the changes in gene expression involved in the action of antidepressant drugs on memory have not been identified, in this study we investigated the impact of chronic treatment with a SSRI (fluoxetine) and a SNRI (venlafaxine) on the mRNA expression of genes related to memory cascade in the mouse hippocampus, namely, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), nitric oxide synthase 1 (NOS1), neurotrophic tyrosine kinase receptor type 2 (TrKB), mitogen-activated protein kinases (MAPK/ERK) and serotonin transporter (SERT). Animals treated with fluoxetine 10 mg/Kg/day for 28 days showed a significant decrease in the percentage of time spent in the novel object recognition test (p≤0.005) and induced MAPK1/ERK2 down-regulation (p=0.005). Our results suggest that the effect on cognition could probably be explained by fluoxetine interference in the MAPK/ERK memory pathway. In contrast, chronic treatment with venlafaxine did not reduce MAPK1/ERK2 expression, suggesting that MAPK1/ERK2 down-regulation is not a common effect of all antidepressant drugs. Further studies are needed to examine the effect of chronic fluoxetine treatment on the ERK-CREB system, and to determine whether there is a causal relationship between the disruption of the ERK-CREB system and the effect of this antidepressant on memory performance.

Location is everything: neurons born during fluoxetine treatment accumulate in regions that do not support spatial learning

It is well known that antidepressants both improve mood and increase the rate at which the dentate gyrus (DG) generates new neurons. In addition to the implications of neurogenesis for mood regulation, the production and survival of granule cells has also been implicated in learning and memory. Despite this evidence, the results of studies on the effect of antidepressants on memory have been mixed. A critical piece of data that may be missing from previous studies, however, is insight into (a) the location that newborn neurons migrate to following fluoxetine administration and (b) their ability to express normal patterns of activity-related genes. Here we demonstrate a finding that may resolve the discrepancy in the effects fluoxetine-induced neurogenesis on mood and memory: after 5 weeks delay, the net additional neurons generated in animals given the antidepressant fluoxetine during treatment are functionally normal, but preferentially accumulate (due to changes in migration and/or survival) in an area of the DG that is not recruited by spatial memory tasks.

Fluoxetine and the dentate gyrus: memory, recovery of function, and electrophysiology

Chronic fluoxetine increases neurogenesis in the dentate gyrus (DG). In view of the widespread clinical use of fluoxetine and the well-established role of the DG in memory, surprisingly few studies have examined the effects of fluoxetine on memory and hippocampal electrophysiology. Additionally, few studies have evaluated the potential for fluoxetine to promote recovery of function after DG damage. Therefore, we studied the effects of long-term administration of fluoxetine on both spatial-reference memory and working memory, recovery of function after intrahippocampal colchicine infusions, which can destroy 50-70% of DG granule cells, and electrophysiological responses in the DG to perforant path stimulation in freely moving rats. Chronic fluoxetine did not affect matching-to-place or reference-memory performance in intact rats in the Morris water-maze task. Surprisingly, in rats with DG damage, recovery of function on both tasks was adversely affected by chronic fluoxetine. Finally, unlike an earlier study that reported fluoxetine-induced increases in hippocampal population spike amplitudes and excitatory postsynaptic potential slopes in urethane-anesthetized rats, electrophysiological measures in DG of freely moving rats were not affected by chronic fluoxetine treatment.

Fluoxetine monotherapy in attention-deficit/hyperactivity disorder and comorbid non-bipolar mood disorders in children and adolescents

Children with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for developing comorbid non-bipolar mood disorders. Fluoxetine monotherapy is an established treatment for pediatric mood disorders; however its efficacy in ADHD and comorbid mood disorder is unknown. Therefore, we evaluated 30 children who met DSM-IV criteria for ADHD and comorbid non-bipolar mood disorders in a prospective, 6-12-week open-label, study of fluoxetine monotherapy. Fluoxetine was associated with significant decreases in the severity of depressive symptoms, and also, associated with significant decreases on subscales of inattention/overactivity and aggression/defiant symptoms-47% of participants were much or very much improved without observed adverse effects.

SSRIs and cognitive performance in a working sample

BACKGROUND

Studies of the impact of antidepressant use on cognitive performance have frequently been carried out among the elderly or on healthy volunteers. Comparatively little research has considered their impact on a relatively young, working population, particularly within the context of everyday life.

AIMS

To examine any association between SSRI use and cognitive performance, mood and human error at work.

METHODS

SSRI users and controls completed a battery of laboratory based computer tasks measuring mood and cognitive function pre- and post-work at the start and end of a working week. They also completed daily diaries reporting their work performance.

RESULTS

SSRI use was associated with memory impairment: specifically poorer episodic, though not working or semantic memory. Effects of SSRI use on recognition memory seemed to vary according to the underlying psychopathology, while effects on delayed recall were most pronounced among those whose symptoms had not (yet) resolved. There were no detrimental effects on psychomotor speed, attention, mood or perceived human error at work.

CONCLUSIONS

The findings lend support to the SSRIs comparative safety, even among workers, particularly as the symptoms of the underlying psychopathology are successfully addressed. Possible memory impairments may, however, be found in those taking SSRIs.

Fluoxetine-induced memory impairment in four family members

OBJECTIVE

Fluoxetine, a selective serotonin reuptake inhibitor antidepressant agent, has been implicated in learning and memory. Here, we report four cases from the same family of fluoxetine-related memory-impairment.

RESULTS

Memory-impairment resulted after fluoxetine treatment and disappeared after changing to another selective serotonin reuptake inhibitor.

CONCLUSIONS

There may be a relationship between fluoxetine-related memory impairment and genetic factors, and this side-effect appears to be specific to fluoxetine treatment. Possible mechanisms underlying this effect may be the drug's influence on the central serotonergic system or brain-derived neurotrophic factor.

Memory Loss in a Patient Treated with Fluoxetine

OBJECTIVE

To report a case of severe memory loss in an elderly patient after initiation of fluoxetine.

CASE SUMMARY

An 87-year-old white woman was started on fluoxetine for depression, and the dose was titrated to 20 mg/d. She developed progressive memory loss over the next 6 weeks for which she ultimately was hospitalized. Other potential causes for her memory loss were ruled out. After fluoxetine was discontinued, the patient's memory improved significantly over the next 2 months. An objective causality assessment indicated a possible relationship between the memory loss and fluoxetine in this patient.

DISCUSSION

Our report documents a case of severe reversible memory deterioration after initiating fluoxetine. Fluoxetine has a favorable adverse effect profile when compared with older classes of antidepressants. Postmarketing studies and isolated case reports, however, suggest that fluoxetine may harm memory in some patients. Some selective serotonin-reuptake inhibitors (SSRIs) appear to cause memory loss more frequently than others.

CONCLUSIONS

Clinicians should be aware of the possible effects of fluoxetine (and possibly other SSRIs) on memory.

Neuropsychological performance in medicated vs. unmedicated patients with obsessive-compulsive disorder

To date, there have been no formal investigations of neuropsychological performance in patients with obsessive-compulsive disorder (OCD) taking psychotropic medications. The purpose of this study was to determine whether medicated and unmedicated patients with OCD demonstrate differences in neuropsychological functioning. Fifty-two patients with a primary DSM-IV diagnosis of OCD participated in the study; 28 were taking serotonin reuptake inhibitors (SRIs), and 24 were treatment-naïve (n=8) or had finished a washout period prior to their inclusion in other studies (n=16). The groups were well matched with regard to demographic and clinical variables, including symptom severity. Each group was administered a comprehensive neuropsychological battery to assess general intelligence, attention, verbal and non-verbal working memory, declarative and procedural learning, visuo-constructive skills, and executive functions. SRI-medicated did not differ from SRI-free patients on any neuropsychological measure. Benzodiazepines seemed to improve the patients' functioning on a semantic verbal fluency test. In addition, there were significant interactions between SRIs and benzodiazepines on the perseverative errors of the Wisconsin Card Sorting Test and on reaction times. SRI-medicated patients with OCD are able to perform on cognitive functioning tests at a comparable level with that of SRI-free patients, and these results have positive implications for OCD patients who respond to SRIs. The interactions between SRIs and benzodiazepines and their effect on cognition in OCD are likely to be complex and deserve further study.

Pharmacological treatment of depression in children and adolescents

Major depression is a common disorder during childhood and adolescence. Over the past decade, many new antidepressants have been marketed in the US. In adults, these newer agents have been shown to be as effective as the prototypic tricyclic antidepressants (TCAs). Further, when compared with the TCAs these medications are better tolerated and are safer in overdose. Although TCAs are effective in the treatment of depressed adults, controlled clinical trials have not demonstrated their efficacy in either children or adolescents. In addition, concerns about the safety of TCAs and the monoamine oxidase inhibitors has left disappointingly few pharmacological treatment options available for depressed children and adolescents. For this reason, clinicians have begun to prescribe the newer agents for this population, despite the fact that relatively little is known about their disposition, safety or effectiveness in the young. Investigators have begun to examine whether the use of newer antidepressant medications such as fluoxetine, sertraline, paroxetine, fluvoxamine, nefazodone, and venlafaxine is truly indicated for children and adolescents with major depression. Pharmacokinetic studies of sertraline, paroxetine and nefazodone have been performed in depressed youths. The results of these studies have provided data for rational administration strategies for these agents. They have also provided evidence that these agents may be well tolerated in children and adolescents. Further evidence that these agents are often well tolerated when prescribed to depressed youths has been obtained from both open-label and double-blind studies. Published studies have generally shown that open-label treatment with these newer agents often leads to symptom amelioration in paediatric patients with major depression. Since high rates of placebo response are often seen in depressed children and adolescents, results from these studies cannot be interpreted to suggest that these medications have true antidepressant efficacy in this population. At present, the results of only two such studies have been published. The results of one of these trials are difficult to interpret because of methodological considerations. The other study reported that treatment with fluoxetine was superior to placebo. This paper critically reviews what has been published about the pharmacological treatment of depressed paediatric patients and provides some guidance to the use of antidepressants in this patient population, paying particular attention to what is known about the newer antidepressants as well as considering directions for future research.

Selective serotonin reuptake inhibitors in the treatment of affective disorders--III. Tolerability, safety and pharmacoeconomics

The clinical use of tricyclic antidepressants (TCAs) is often complicated by toxicity and safety problems due to their effects on multiple mechanisms of action, many of which are unnecessary for therapeutic effect. The development of the selective serotonin reuptake inhibitors (SSRIs), with their selective mode of action, has resulted in a class of antidepressant drugs possessing an improved side-effect profile, while retaining good clinical efficacy. Their introduction into clinical practice has led to enhanced patient compliance with antidepressant therapy and the ability to maintain treatment over longer periods of time at an adequate therapeutic dose. Although, as a result of their selective action, side-effects associated with SSRI therapy are minimised, distinct variations between individual SSRIs in terms of their tolerability profiles have been observed. The wealth of clinical data now available has revealed differences in their potential to cause psychiatric and neurological side-effects, dermatological reactions, anticholinergic side-effects, changes in body weight, sexual dysfunction, cognitive impairment, discontinuation reactions and drug-drug interactions. Patients who suffer from concomitant depression and physical illness may experience different tolerability profiles, in addition to the greater likelihood that they will be receiving concomitant medications with the potential for pharmacokinetic drug-drug interactions with coadministered SSRI therapy. In addition, the safety margin of SSRIs in overdose may vary within the group. Knowledge of the differences that exist among the SSRIs in respect of tolerability and safety will aid physicians in the selection of the most beneficial treatment strategy for their patients. A successful clinical outcome leads to a reduced economic burden for the patient, their family and the healthcare services. Thus, pharmacoeconomic considerations are also important in choosing antidepressant therapy. The SSRIs, despite relatively higher prescription costs, have been demonstrated to be a more cost-effective option than the TCAs. Furthermore, there is evidence that the emerging clinical differences between SSRIs may translate into significantly different economic outcomes within the group.

SSRI-induced extrapyramidal side-effects and akathisia: implications for treatment

The selective serotonin reuptake inhibitors (SSRIs) may occasionally induce extrapyramidal side-effects (EPS) and/or akathisia. This may be a consequence of serotonergically-mediated inhibition of the dopaminergic system. Manifestations of these effects in patients may depend on predisposing factors such as the presence of psychomotor disturbance, a previous history of drug-induced akathisia and/or EPS, concurrent antidopaminergic and/or serotonergic therapy, recent monoamine oxidase inhibitor discontinuation, comorbid Parkinson's disease and possibly deficient cytochrome P450 (CYP) isoenzyme status. There is increasing awareness that there may be a distinct form of melancholic or endogenous depression with neurobiological underpinnings similar to those of disorders of the basal ganglia such as Parkinson's disease. Thus, it is not surprising that some individuals with depressive disorders appear to be susceptible to developing drug-induced EPS and/or akathisia. In addition, the propensity for the SSRIs to induce these effects in individual patients may vary within the drug class depending, for example, on their selectivity for serotonin relative to other monoamines, affinity for the 5-HT2C receptor, pharmacokinetic drug interaction potential with concomitantly administered neuroleptics and potential for accumulation due to a long half-life. The relative risk of EPS and akathisia associated with SSRIs have yet to be clearly established. The potential risks may be reduced by avoiding rapid and unnecessary dose titration. Furthermore, early recognition and appropriate management of EPS and/or akathisia is required to prevent the impact of these effects on patient compliance and subjective well-being. It is important that the rare occurrence of EPS in patients receiving SSRIs does not preclude their use in Parkinson's disease where their potentially significant role requires more systematic evaluation.

New antidepressant drugs and the treatment of depression in the medically ill patient

The advent of the SSRIs, venlafaxine, bupropion, and nefazodone, has greatly expanded pharmacologic treatment options for the depressed medically ill patient. Although the relatively benign side effects of these medications on cardiac conduction and blood pressure allow for more liberal use in the medically ill, these drugs nevertheless have different capacities for adverse drug interactions that must be considered. Nevertheless, such interactions can usually be avoided or managed by knowledgeable clinicians cognizant of the pharmacodynamic and pharmacokinetic principles outlined in this article.