Fenfluramine treatment of autism

Practical Paediatric Psychopharmacological Prescribing in Autism

Claims of ‘miracle cures’ for autism in the press and on the Internet bring new pressures to bear on parents of children with autism, and the professionals who care for them. Between a third and a half of people with autism in America are receiving some psychotropic medication. Despite recent advances in paediatric psychopharmacology, there is no proof that any medication can target the primary social impairments that characterize autism. The article discusses the evidence behind two approaches to psychopharmacological management in children with autism. The first approach selects certain target symptoms such as resistance to change, ritualistic/compulsive behaviours, hyperactivity, aggressive behaviours and sleep problems. The evidence for the effectiveness of agents including stimulants, anti- depressants, and melatonin when used to treat these symptoms is appraised. The second approach attempts to treat or cure the primary social impairment underlying autism. The evidence for the effectiveness of agents including naltrexone, fenfluramine and secretin is appraised. Early reports in this field have generated false hope, and the need for well-designed larger multicentre trials is emphasized.

Behavioral and cellular consequences of increasing serotonergic activity during brain development: a role in autism?

The hypothesis explored in this review is that the high levels of serotonin in the blood seen in some autistic children (the so-called hyperserotonemia of autism) may lead to some of the behavioral and cellular changes also observed in the disorder. At early stages of development, when the blood-brain Barrier is not yet fully formed, the high levels of serotonin in the blood can enter the brain of a developing fetus and cause loss of serotonin terminals through a known negative feedback function of serotonin during development. The loss of serotonin innervation persists throughout subsequent development and the symptoms of autism appear. A review of the basic scientific literature on prenatal treatments affecting serotonin is given, in support of this hypothesis, with an emphasis on studies using the serotonin agonist, 5-methoxytryptamine (5-MT). In work using 5-MT to mimic hyperserotonemia, Sprague-Dawley rats are treated from gestational day 12 until postnatal 20. In published reports, these animals have been found to have a significant loss of serotonin terminals, decreased metabolic activity in cortex, changes in columnar development in cortex, changes in serotonin receptors, and "autistic-like" behaviors. In preliminary cellular findings given in this review, the animals have also been found to have cellular changes in two relevant brain regions: 1. Central nucleus of the amygdala, a brain region involved in fear-responding, where an increase in calcitonin gene related peptide (CGRP) was found 2. Paraventricular nucleus of the hypothalamus, a brain region involved in social memory and bonding, where a decrease in oxytocin was found. Both of these cellular changes could result from loss of serotonin innervation, possibly due to loss of terminal outgrowth from the same cells of the raphe nuclei. Thus, increased serotonergic activity during development could damage neurocircuitry involved in emotional responding to social stressors and may have relevance to the symptoms of autism.

Risperidone treatment of children with autistic disorder: effectiveness, tolerability, and pharmacokinetic implications

BACKGROUND

Recent evidence indicates that atypical antipsychotics represent a promising option for the treatment of autistic disorder. In particular, risperidone appears to be effective in treating aggressiveness, hyperactivity, irritability, stereotypies, social withdrawal, and lack of interests.

OBJECTIVE

The aim of the present study was to evaluate the effectiveness and tolerability of risperidone in children with autistic disorder and to examine the correlation between plasma levels of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) and the clinical response.

METHODS

The effect of treatment with risperidone (0.75-2 mg/day; mean +/- SD dose = 1.26 +/- 0.42 mg/day) was studied for 24 weeks in 20 children (14 boys, 6 girls) ages 3 to 10 years (mean age 6.0 +/- 2.4 years), diagnosed with autistic disorder. Fourteen items selected from the Children's Psychiatric Rating Scale (CPRS-14) and Clinical Global Impression (CGI) were used for behavioral evaluation. Patients were classified as responders if they showed a 25% or greater decrease on CPRS-14 total score at final evaluation compared with baseline and a final CGI rating of 1 or 2. Patients were rated for extrapyramidal side effects on the Abnormal Involuntary Movement Scale (AIMS). Other side effects, including the expected side effects of atypical antipsychotics drugs, were assessed by a checklist. Blood samples for determination of risperidone and its active metabolite 9-OH-risperidone were obtained after 12 weeks, and serum prolactin levels were measured on admission and at weeks 12 and 24.

RESULTS

The psychopathological state, as assessed by CPRS, improved significantly over the duration of treatment. The mean CPRS-14 scores decreased significantly from 63.7 +/- 10.0 at baseline to 52.9 +/- 14.3 at week 12 (p < 0.01). At the end of 12 weeks of treatment, 8 patients were considered responders, and 10 patients reached a minimal improvement. No further improvement was observed in the following 12 weeks. In all children, serum prolactin levels increased significantly (p < 0.001) from 166 +/- 88 UI/mL at baseline to 504 +/- 207 UI/mL at week 12 of risperidone treatment. Weight gain and increased appetite were the most common unwanted effects. A mean increase of 3.7 +/- 1.7 kg in body weight was observed at final evaluation as compared with baseline. There was no significant correlation between percent improvement in total CPRS score and the plasma level of risperidone's active fractions (the sum of the risperidone and 9-OH-risperidone plasma concentration).

CONCLUSIONS

This study provides further evidence of the beneficial effects of risperidone in children diagnosed with autistic disorder. However, the potential advantages of risperidone should be weighed against the risk of unwanted effects, such as an increase in serum prolactin levels and weight gain. No relation was observed between total plasma risperidone and 9-OH-risperidone concentrations and clinical response.

Pervasive developmental disorders: a 10-year review

OBJECTIVE

To summarize recent advances about the nature, diagnosis, and treatment of pervasive developmental disorders.

METHOD

Review of Medline databases, books, and book chapters published between July 1989 and November 1999.

RESULTS

Clinical and genetic studies support expansion of the concept of autism to include a broader spectrum of social communication handicaps. The prevalence of autism is approximately 1 per 2,000; the prevalence of autism and Asperger's disorder together is 1 per 1,000. The Checklist for Autism in Toddlers is a useful screening instrument for 18-month-old children; the Autism Diagnostic Interview-Revised and the Autism Diagnostic Observation Schedule are instruments of choice for research. Although twin and family studies clearly support genetic factors as important in autism, linkage analysis studies indicate that many genes may be involved. There is no one treatment of choice. Social-pragmatic approaches, augmented by individualized strategies and social coaching, may be best for teaching social communication skills. Pharmacological interventions have a limited role in improving social communication, but selective serotonin reuptake inhibitors and atypical neuroleptic medications may help ameliorate aggression, hyperactivity, and other secondary problems.

CONCLUSIONS

Private and government agencies must continue to support basic and applied research.

The Effect of Selective Serotonin Releasing Agents in the Chronic Mild Stress Model of Depression in Rats

Chronic exposure to mild unpredictable stress has been found to depress the consumption of, and preference for, highly palatable sucrose solution in rats. Stress-induced behavioral deficits may be maintained for a long time, however chronic administration of clinically effective antidepressants can restore normal behavior. This is the first report showing that Sprague-Dawley rats can be used in this model. A preference deficit in this strain of rats took at least 7 weeks to develop; about twice the time required when hooded Lister or Wistar rats are used in this model. Water consumption was not effected by chronic exposure to the mild stress regime and/or by chronic administration of the selective serotonin (5-HT) releasing agent MMAI (5-methoxy-6-methyl-2-aminoindan). The stress-induced deficit in sucrose intake was completely reversed by chronic treatment with MMAI (5 mg/kg, 2 x day) over 3 weeks in the two-bottle tests. In single-bottle tests, chronic treatment with the selective 5-HT releasers, MMAI (5 mg/kg, 2 x day) or MTA (p-methylthioamphetamine; 5 mg/kg, 2 x day), reversed the deficit in rewarded behavior (anhedonia) measured as a decrease in the consumption of 1% sucrose solution in the chronic mild stress model of depression in rats. With the experimental procedure employed, and at a dose of 10 mg/kg/day of 5-HT releasers, the magnitude and onset of this effect were greater than observed following similar administration of the selective 5-HT reuptake inhibitor (SSRI) sertraline (10 mg/kg/day), used as a standard anti-depressant drug.

Autism research: prospects and priorities

Research prospects and priorities in the field of autism are discussed with respect to (a) diagnosis, classification, and epidemiology; (b) clinical research; (c) neuropsychological research; (d) genetics; (e) structural and functional brain imaging; (f) postmortem studies; (g) other biological research; and (h) treatment research. Also, it is argued that research into autism has a priority in the broader field of developmental psychopathology because it carries the promise of throwing light on casual mechanisms that apply beyond the syndrome of autism.

Treatment of autistic disorder

OBJECTIVE

To present an overview of a variety of treatment approaches in individuals with autistic disorder.

METHOD

Selected studies and articles are reviewed.

RESULTS

In the past three decades, great progress has been made in the treatment of autistic disorder, particularly in the area of education and parental involvement, with the objective to transfer to home and in other situations learning acquired in school. A role for psychoactive agents, when combined with psychosocial treatments, has been identified.

CONCLUSIONS

Although considerable advances have been made in a variety of interventions-educational, psychosocial, and biological-knowledge about the comparative and combined efficacy of the various treatment modalities is lacking. From the parents' perspective, particularly, support and continuity of services require improvement.

Fenfluramine and methylphenidate in children with mental retardation and ADHD: clinical and side effects

Each of 28 nonautistic children with attention-deficit hyperactivity disorder and mental retardation received placebo, methylphenidate (0.4 mg/kg/day), and fenfluramine (gradually increased to 1.5 mg/kg/day) for 4 weeks each in a double-blind, crossover design. Teacher ratings indicated significant improvements with both active drugs on subscales designated as Conduct Problem, Hyperactivity, and Irritability, but methylphenidate alone produced improvements on an Inattention subscale. Parent ratings indicated significant improvements with both drugs on subscales labeled Hyperactivity, Motor Excess, and Conduct Problem. Fenfluramine alone caused improved parent ratings on Irritability and Inappropriate Speech, and on Conners' Abbreviated Symptom Questionnaire. Unlike a previous study, subgroup analyses failed to show a significantly better clinical response to methylphenidate for subjects with higher mental ages, although children with higher IQs responded better than those with IQs less than 45. The active drugs had contrasting effects on heart rate and blood pressure. Fenfluramine caused significant weight reductions relative to both placebo and methylphenidate. These findings suggest that both methylphenidate and fenfluramine have useful, but somewhat different, clinical effects in certain children with attention-deficit hyperactivity disorder and mental retardation.

New evidence for a loss of serotonergic nerve terminals in rats treated with d,l-fenfluramine

Fenfluramine has been classified as a neurotoxin because animals treated with this anorectic lose 5-HT uptake sites located on serotonergic nerve terminals. However, there are two possible bases for this finding: either uptake sites are lost because the terminals themselves have been destroyed (neurotoxicity); or uptake sites are lost from otherwise intact terminals. To distinguish between these possibilities, we established an animal model in which male Wistar rats were injected (intraperitoneally) with an irreversible 5-HT uptake site antagonist (EEDQ). Since their 5-HT sites were inhibited (blocked) non-competitively, by this agent, such animals had effectively lost 5-HT uptake sites from intact serotonergic terminals. Synaptosomes prepared from such animals showed the predicted reduction in the Bmax of [3H]paroxetine binding to the 5-HT uptake site, and a reduction in the Vmax of [14C]5-HT uptake. However, they showed no significant reduction in maximal [14C]5-HT loading (alpha) compared with synaptosome from sham-injected controls. In contrast, fenfluramine-treated animals showed reduced [3H]paroxetine binding, reduced maximal [14C]5-HT uptake and significantly (P < 0.02) reduced synaptosomal [14C]5-HT loading. Therefore, the results suggest that fenfluramine does indeed cause the destruction of serotonergic nerve terminals.

Pediatric psychopharmacotherapy: a review of recent research

In the past 5 years, we have witnessed the continuation of important trends in clinical research that began earlier in the decade. With regard to the treatment of specific disorders in children and adolescents, the most significant developments have been the examination of the tricyclics for the treatment of depression and the initiation of controlled studies for the treatment of Tourette syndrome. Unfortunately, the findings from the depression studies have been uniformly negative, and the results of research on both depression and tic disorders show a relatively high rate of placebo responsivity, which raises nagging questions about the role of case reports and open trials. Another important trend in pediatric psychopharmacotherapy is the search for substitutes for the neuroleptics. Potential candidates include agents such as lithium, naltrexone, fenfluramine, clonidine, and carbamazepine. The most underresearched disorders are a combination of the least common (e.g. schizophrenia, mania) and those that are apparently perceived as less serious (e.g. sleep disorders, certain anxiety disorders). Not surprisingly, the most studied disorder and treatment is hyperactivity and stimulant medication, respectively. Considerable progress has been made in understanding the social implications of the associated symptoms and their response to stimulant drugs, aided greatly by the use of direct observation procedures. Researchers are beginning to attend to the implications of comorbidity for assessing response to medication. There has been additional confirmation of efficacy of stimulant treatment for preschoolers and adolescents. Dose-response issues remain to some extent unresolved, the primary impediments being interpretive misconceptions associated with trend analysis, an overreliance on the syndromal perspective and too little attention to target behaviors and their clinical implications, and the failure to operationalize the minimal effective dose with regard to the normalization and supranormalization of target and collateral behaviors. Disagreement over whether hyperactivity is a learning or a behavior disorder (or both) and what academic underproductivity means clinically and socially is also impeding progress. With regard to developmental disorders, controlled studies indicate that fenfluramine and naltrexone are effective for managing associated symptoms in some individuals. However, given the limited amount of research on these agents, their status as clinically useful palliatives must be considered tentative.(ABSTRACT TRUNCATED AT 400 WORDS)

Diagnostic and assessment issues related to pharmacotherapy for children and adolescents with autism

Autism involves not only developmental delays but also aberrant behavior, both of which change in nature over time. Rating instruments may be useful to assess maladaptive and adaptive behaviors of autistic children in a standardized way and, perhaps, to measure change due to treatment. With the expansion of basic science, knowledge, and technology, there is increasing evidence that autism is etiologically heterogeneous. Currently, there is no biological marker specific to autism, although hyperserotonemia is a consistent finding in one third of autistic children. An aim of basic science research has been to develop a rational pharmacotherapy based upon the underlying neurochemistry. However, at the present time, this approach has not always been successful. It is expected that the development and use of more restrictive criteria, delineation of subtypes of autism, and interaction of descriptive, behavioral, clinical, and basic research will lead to more effective planning for treatment. The relationship of assessment to treatment response is presented and discussed.

A novel biochemical model linking dysfunctions in brain melatonin, proopiomelanocortin peptides, and serotonin in autism

A novel biochemical model for autism is presented, which proposes that a subgroup of autistic individuals may have a hypersecretion of pineal melatonin that produces a cascade of biochemical effects including a corresponding hyposecretion of pituitary proopiomelanocortin (POMC) peptides and a hypersecretion of hypothalamic opioid peptides and serotonin (5-HT). The model is reviewed, and supporting animal and clinical research, is summarized. The first arm of the model suggests that increases in pineal melatonin results in hypersecretion of 5-HT in hypothalamus and blood. The second arm of the model indicates that hypersecretion of melatonin also inhibits the release of hypothalamic corticotrophin-releasing hormone (CRH). Hyposecretion of CRH may result in decreased release of both pituitary B-endorphin (B-E) and adrenocorticotrophin hormone (ACTH); this, in turn, may result in decreased plasma concentrations of B-E, ACTH, and cortisol. In autism, a genetically determined hypersecretion of hypothalamic B-E may further contribute to an inhibition of pituitary B-E because of negative feedback inhibition. Therefore, autism may reflect a dysfunction in the pineal-hypothalamic-pituitary-adrenal axis which, modulates POMC and 5-HT systems of the brain. This model is consistent with numerous clinical investigations implicating hypersecretion of brain 5-HT and opioid peptides in autism. The model may have heuristic importance in guiding future research in the biochemistry of autism.

Effects of fluoxetine or D-fenfluramine on serotonin release from, and levels in, rat frontal cortex

Using in vivo microdialysis of frontal cortex in anesthetized rats, as well as analysis of frontal cortex homogenates, we examined the effects of chronic administration of fluoxetine (30 mg/kg, i.p.) or D-fenfluramine (7.5 mg/kg, i.p.), administered daily for 3 days, on serotonin and 5-HIAA levels a day later. Measurements were also taken after 3-, 7- , and 21-day recovery periods. Neither chronic fluoxetine nor D-fenfluramine changed basal serotonin release. Both treatments, however, transiently decreased the release of serotonin evoked by an acute dose of D-fenfluramine (10 mg/kg, i.p.). Release initially was completely suppressed in fluoxetine-pretreated animals but returned to normal by the 21st day of washout; following D-fenfluramine pretreatment, normal release was attained by the 7th day of washout. Both fluoxetine and D-fenfluramine transiently decreased 5-HIAA levels in the dialysates and tissues. Both drugs also caused prolonged changes in frontal cortex serotonin levels, D-fenfluramine lowering them but fluoxetine elevating them. These results suggest that, at comparable dosage levels relative to their ED50s, fluoxetine and D-fenfluramine cause comparable reversible effects on brain serotonin release. The drugs also cause prolonged but opposite changes in brain serotonin levels, probably reflecting differences in the extents to which they or their principal metabolites release serotonin and block its reuptake.

A controlled crossover trial of fenfluramine in autism

We report a 12 month double-blind randomized crossover trial of fenfluramine in 20 children with the syndrome of autism. On active drug most of the children lost weight and blood serotonin levels fell by an average of 60%. There was a fall in urinary dopamine (DA) and noradrenaline (NA) levels and increased excretion of homovanillic acid (HVA). Some of the children showed improvement in tests of cognitive and language function, although the results did not achieve overall statistical significance. Event-related brain potentials (ERPs) were obtained in seven subjects on an auditory choice reaction time task. Side effects of the drug included irritability and lethargy. Fenfluramine may have a limited place in the management of some patients with autistic disorder.

Infantile autism: diagnosis and treatment

This article reviews recent developments in the diagnosis and treatment of infantile autism. Autism is currently conceptualized as a behavioural syndrome with multiple biological aetiologies. A diagnosis of infantile autism implies that a thorough neurobiological investigation is called for. The core psychological deficit necessary and sufficient to cause central autism symptoms is gradually being defined. The multiple aetiologies of autism will lead to multiple treatment in the future. At the present stage structured education and behaviour modification provide the cornerstones of any treatment programme.

Effects of high-dose fenfluramine treatment on monoamine uptake sites in rat brain: assessment using quantitative autoradiography

Fenfluramine is an amphetamine derivative that in humans is used primarily as an anorectic agent in the treatment of obesity. In rats, subchronic high-dose d,l-fenfluramine treatment (24 mg/kg subcutaneously, twice daily for 4 days) causes long-lasting decreases in brain serotonin (5HT), its metabolite 5-hydroxyindoleacetic acid, and high-affinity 5HT uptake sites. Moreover, this high-dose treatment regimen causes both selective long-lasting decreases in fine-caliber 5HT-immunoreactive axons and appearance of other 5HT-immunoreactive axons with morphology characteristic of degenerating axons. Determination of the potential neurotoxic effects of fenfluramine treatment using immunohistochemistry is limited from the perspectives that staining is difficult to quantify and that it relies on presence of the antigen (in this case 5HT), and the 5HT-depleting effects of fenfluramine are well known. In the present study, we used quantitative in vitro autoradiography to assess, in detail, the density and regional distribution of [3H]paroxetine-labeled 5HT and [3H]mazindol-labeled catecholamine uptake sites in response to the high-dose fenfluramine treatment described above. Because monoamine uptake sites are concentrated on monoamine-containing nerve terminals, decreases in uptake site density would provide a quantitative assessment of potential neurotoxicity resulting from this fenfluramine treatment regimen. Marked decreases in densities of [3H]paroxetine-labeled 5HT uptake sites occurred in brain regions in which fenfluramine treatment decreased the density of 5HT-like immunostaining when compared to saline-treated control rats. These included cerebral cortex, caudate putamen, hippocampus, thalamus, and medial hypothalamus. Smaller, but nonetheless significant, decreases in density of [3H]paroxetine-labeled 5HT uptake sites were noted in brain regions in which partial sparing of 5HT-like immunoreactive fibers had been reported following fenfluramine treatment, specifically septum, lateral hypothalamus, and amygdala. In contrast, [3H]mazindol autoradiography revealed that total catecholamine (i.e., dopamine and norepinephrine) uptake sites in cerebral cortex, caudate putamen, and locus coeruleus, areas in which [3H]paroxetine-labeled 5HT uptake sites were significantly decreased, were unaffected by this fenfluramine treatment. These data support the hypothesis that subchronic, high-dose fenfluramine treatment causes selective degeneration of 5HT axons in rat brain. Since pharmacokinetic studies show that the dosing regimen used in this study exposes rat brain to concentrations of fenfluramine that are approximately 600 times greater than those resulting from the therapeutic oral dose, caution must be exercised in extrapolating these data to humans.