Drugs of dependence though not of abuse: fenfluramine and imipramine

Structural and functional perspectives on interactions between synthetic cathinones and monoamine transporters

Synthetic cathinone derivatives comprise a family of psychoactive compounds structurally related to amphetamine. Over the last decade, clandestine chemists have synthesized a consistent stream of innovative cathinone derivatives to outpace governmental regulatory restrictions. Many of these unregulated substances are produced and distributed as designer drugs. Two of the principal chemical scaffolds exploited to expand the synthetic cathinone family are methcathinone and α-pyrrolidinopentiophenone (or α-pyrrolidinovalerophenone, α-PVP). These compounds' main physiological targets are monoamine transporters, where they promote addiction by potentiating dopaminergic neurotransmission. This chapter describes techniques used to study the pharmacodynamic properties of cathinones at monoamine transporters in vitro. Biochemical techniques described include uptake inhibition and release assays in rat brain synaptosomes and in mammalian expression systems. Electrophysiological techniques include current measurements using the voltage clamp technique. We describe a Ca2+ mobilization assay wherein voltage-gated Ca2+ channels function as reporters to study the action of synthetic cathinones at monoamine transporters. We discuss results from systematic structure-activity relationship studies on simple and complex cathinones at monoamine transporters with an emphasis on identifying structural moieties that modulate potency and selectivity at these transporters. Moreover, different profiles of selectivity at monoamine transporters directly predict compounds associated with behavioral and subjective effects within animals and humans. In conclusion, clarification of the structural aspects of compounds which modulate potency and selectivity at monoamine transporters is critical to identify and predict potential addictive drugs. This knowledge may allow prompt allocation of resources toward drugs that represent the greatest threats after drugs are identified by forensic laboratories.

Dreams, Sleep, and Psychotropic Drugs

Over the past 60 years, the impact of psychotropic drugs on dream recall and content has been scarcely explored. A review of the few existing experimental results on the topic leads us to the following conclusions. For antidepressant drugs, in the great majority, they reduce dream recall frequency (DRF), and the improvement of depressive symptoms is associated with an increase of positive emotion in dream content. For sedative psychotropic drugs, their improvement of sleep quality is associated with a reduction of DRF, but the effect on dream content is less clear. Few occurrences of nightmare frequency increase have been reported, with intake of molecules disturbing sleep or with the withdrawal of some psychotropic drugs. Importantly, the impact of psychotropic drugs on rapid eye movement (REM) sleep does not explain DRF modulations. The reduction of intra-sleep awakenings seems to be the parameter explaining best the modulation of DRF by psychotropic drugs. Indeed, molecules that improve sleep continuity by reducing intra-sleep awakenings also reduce the frequency of dream recall, which is coherent with the “arousal-retrieval model” stating that nighttime awakenings enable dreams to be encoded into long-term memory and therefore facilitate dream recall. DRF is nonetheless influenced by several other factors (e.g., interest in dreams, the method of awakening, and personality traits), which may explain a large part of the variability of results observed and cited in this article.

Post-SSRI Sexual Dysfunction: A Bioelectric Mechanism?

Selective serotonin reuptake inhibitor (SSRI) drugs, targeting serotonin transport, are widely used. A puzzling and biomedically important phenomenon concerns the persistent sexual dysfunction following SSRI use seen in some patients. What could be the mechanism of a persistent physiological state brought on by a transient exposure to serotonin transport blockers? In this study, we briefly review the clinical facts concerning this side effect of serotonin reuptake inhibitors and suggest a possible mechanism. Bioelectric circuits (among neural or non-neural cells) could persistently maintain alterations of bioelectric cell properties (resting potential), resulting in long-term changes in electrophysiology and signaling. We present new data revealing this phenomenon in planarian flatworms, in which brief SSRI exposures induce long-lasting changes in resting potential profile. We also briefly review recent data linking neurotransmitter signaling to developmental bioelectrics. Further study of tissue bioelectric memory could enable the design of ionoceutical interventions to counteract side effects of SSRIs and similar drugs.

Dreaming under antidepressants: a systematic review on evidence in depressive patients and healthy volunteers

Sleep related symptoms of depression include sleep fragmentation, early morning awakening, decreased rapid eye movement (REM) sleep latency, increased REM density, and more negative dream content. Most tricyclic antidepressants (ADs) increase total sleep time and decrease wake time after sleep onset, while many selective serotonin reuptake inhibitors (SSRIs) have an opposite effect. However, almost all ADs prolong REM sleep latency and reduce the amount of REM sleep. Case reports and research data indicate a strong effect of ADs on dream recall and dream content. We performed a systematic review (1950 to August 2010) about ADs impact on dreaming in depressive patients and healthy volunteers. Twenty-one clinical studies and 25 case reports were eligible for review and document a clear AD effect on dreaming. The major finding, both in depressed patients and in healthy volunteers, is a decrease of dream recall frequency (DRF) under ADs. This is a rather consistent effect in tricyclic ADs and phenelzine, less consistently documented also for SSRIs/serotonin norepinephrine reuptake inhibitors (SNRIs). Tricyclic ADs induce more positive dream emotions. Withdrawal from tricyclic ADs and from the monoamine oxidase inhibitors phenelzine and tranylcypromine may cause nightmares. Intake and even more withdrawal of SSRIs/SNRIs seem to intensify dreaming, which may be experienced in different ways; a potential to cause nightmares has to be taken into account. Though there are clear-cut pharmacological effects of ADs on DRF and dream content, publications have been surprisingly scarce during the past 60 years. There is evidence of a gap in neuropsychopharmacological research. AD effects on dreams should be recognized and may be used in treatment.

Effect of caffeine on sleep: EEG study in late middle age people

1 The effect of caffeine alkaloid base (300 mg) on whole night sleep was investigated by electrophysiological techniques in six late middle age subjects (mean age 56 years), comparison being made with decaffeinated coffee and with no drink prior to sleep, using each condition five times in a balanced order on non-consecutive nights. 2 After caffeine the mean total sleep time decreased on average by 2 h, the mean sleep latency increased to 66 minutes. The number of awakenings increased and the mean total intervening wakefulness was more than doubled after caffeine. 3 In the first 3 h of sleep a decreased amount of stage 3 + 4 was observed, accompanied by an increased amount of stage 2 and of intervening wakefulness, without a significant change in the amount of rapid eye movement sleep. 4 The change in sleep pattern observed suggests an increased capability for arousal and decreased ability to develop or sustain deeper stages of non-rapid eye movement sleep after caffeine.

Conditioned place preference studies with atomoxetine in an animal model of ADHD: effects of previous atomoxetine treatment

To investigate the putative rewarding effects of atomoxetine, a non-stimulant medication for Attention-deficit/hyperactivity disorder (ADHD), we conducted conditioned place preference (CPP) tests in an animal model of ADHD, the spontaneously hypertensive rat (SHR). The effects of drug pre-exposure were also evaluated, thus, parallel experiments were done in rats which have undergone 14 days of atomoxetine treatment. The responses of SHR were compared with the rat strain representing the "normal" heterogeneous population, the Wistar rats. Neither rat strain showed significant CPP to atomoxetine. However, previous atomoxetine treatment produced place preference responses in rats, more profoundly in Wistar rats conditioned with the low and moderate atomoxetine doses. In conclusion, acute exposure to atomoxetine does not have any rewarding effect, however, drug pretreatment produces responses characteristic of reward or psychological dependence, more specifically in the "normal" vs. the ADHD animal model. The present findings call for more studies with atomoxetine, especially those that investigate the effects of long-term or chronic drug treatment.

Quantitative Positron Emission Tomography Studies of the Serotonin Transporter in Humans Previously Treated with the Appetite Suppressants Fenfluramine or Dexfenfluramine

PURPOSE

The appetite suppressants fenfluramine and dexfenfluramine were widely prescribed before being withdrawn from the market in 1997. Both drugs are known to have the potential to damage brain serotonin (5-HT) axons and axon terminals in animals, including nonhuman primates. This study used quantitative positron emission tomography (PET) with [(11)C] McN5652, a serotonin transporter (SERT) ligand to determine whether humans previously exposed to fenfluramines showed reductions in SERT binding parameters.

PROCEDURES

Subjects previously treated with fenfluramines for weight loss (N = 15) and age-matched controls (N = 17) underwent PET studies with [(11)C] McN5652. Global and regional distribution volumes (DVs) of [(11)C] McN5652 were compared in the two subject groups using parametric statistical analyses.

RESULTS

Compared to controls, subjects previously exposed to fenfluramines had significant reductions in [(11)C]McN5652 binding in 14 of 15 regions of interest, more than four years after drug discontinuation.

CONCLUSIONS

These results are the first to provide direct evidence for fenfluramine-induced 5-HT neurotoxicity in humans.

Major depressive episodes and diet pills

A variety of medications used to assist with weight loss have been implicated in the precipitation or induction of depressive symptoms and disorders. This is true of a large number of phenylethylamine agents possessing psychostimulant properties, non-phenylethylamine psychostimulants (e.g., caffeine) and the serotonergic agent, fenfluramine. There is, as yet, no substantial evidence linking the more modern weight loss drugs, sibutramine and orlistat, to the aetiology of major depression. Nevertheless, when these drugs are used, major depression will continue to be an important clinical consideration because of the elevated frequency with which major depression occurs in obese patients, the contribution that major depression may make to poor outcomes in non-pharmacological weight loss treatment and because of the interplay between symptoms of depression and weight loss treatment.

"Diet pills" and major depression in the Canadian population

OBJECTIVE

To evaluate epidemiological associations between self-reported diet pill consumption and major depressive episodes (MDEs), using data from a large-scale, cross-sectional survey of the Canadian population.

METHODS

Data from the National Population Health Survey (NPHS) were used in this analysis. The NPHS interview included a brief version of the Composite International Diagnostic Interview (CIDI) depression section, known as the CIDI Short Form for Major Depression (CIDI-SFMD), as well as provision for self-reported medication use.

RESULTS

Approximately 0.5% of the population reported the use of diet pills. Diet pill use was more common among women than among men. At the time of data collection (1996-1997), the most commonly used medication was fenfluramine (since withdrawn from the market because of cardiovascular toxicity). The use of these medications was strongly associated with MDE: the annual prevalence among persons reporting use was 17.1% (95% CI, 8.6 to 25.6), approximately 4 times the underlying population rate.

CONCLUSIONS

Because the NPHS was a general health survey, and because self-reported exposure to these medications was relatively uncommon, the data did not permit a detailed multivariate analysis. These findings, however, indicate that depressive psychopathology is strongly associated with the use of appetite-suppressant medications.

Pharmacological stress diathesis syndromes

Recent descriptions of discontinuation syndromes following treatment with antidepressants and antipsychotics, in some cases long lasting, challenge both public and scientific models of addiction and drug dependence. Antipsychotic and antidepressant drug dependencies point to a need to identify predisposing constitutional and personality factors in the patient, pharmacological risk factors in the drug and aspects of therapeutic style that may contribute to the development of stress syndromes. The stress syndromes following antipsychotics also point to the probable existence of a range of syndromes emerging within treatment. The characteristics of these need to be established.

Adverse neuropsychiatric events associated with dexfenfluramine and fenfluramine

1. There is a large body of evidence indicating that fenfluramines damage brain serotonin neurons in animals. 2. Little is known about potential adverse neuropsychiatric consequences in humans associated with use of fenfluramines that could potentially be related to serotonergic dysfunction. 3. The authors now report numerous cases of severe and, sometimes persistent, neuropsychiatric syndromes associated with fenfluramine use. 4. Thirty one representative cases are presented and summarized in table form. 5. Several of the cases presented suggest long-lasting deleterious effects of fenfluramines on brain serotonin function. 6. Clinicians should be vigilant for disorders of mood, anxiety, cognitive function and impulse control in patients previously exposed to fenfluramines.

A close look at fenfluramine and dexfenfluramine

In an effort to combat obesity, several medications have been developed. The nonamphetamine anorectics, such as phentermine, fenfluramine, and dexfenfluramine, have been recommended as first-line drug therapy for the treatment of obesity once diet and exercise alone have failed. Numerous studies have shown that these agents can promote weight loss when combined with diet restriction and exercise. Although fenfluramine and dexfenfluramine lack the abuse potential of amphetamine and its congeners, these agents are associated with drug interactions and adverse effects. Concomitant administration of fenfluramine or dexfenfluramine with medications that enhance serotonin levels (e.g., antidepressants, monoamine oxidase inhibitors, and migraine medications) can precipitate serotonin syndrome. Sudden discontinuation of fenfluramine or dexfenfluramine after prolonged administration can precipitate withdrawal depressive symptoms. Primary pulmonary hypertension, a potentially fatal disorder, has been reported to occur approximately 30 times more frequently in patients receiving anorectic agents for more than 3 months compared to the general population. More recently, the association of these popular anorectics with valvular heart disease has caused increased concerns about their use. The risks of primary pulmonary hypertension, valvular heart disease, and the occurrence of convulsions, coma, and death in overdose appear to be equally likely with dexfenfluramine and fenfluramine. In addition, many patients who lose weight while taking these anorectics rapidly regain it after the medication has been discontinued.

Drug-induced depression. Incidence, avoidance and management

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R), drug-induced depression may be classified as an Organic Mood Syndrome, Depressed Type. Unfortunately, the DSM-III-R diagnostic criteria are not sufficiently precise for application in research, and studies of drug-induced depression have rarely utilised these criteria. Research concerned with drug-induced depression is characterised by a number of methodological complications. These include differing definitions of depression, including depression defined as a symptom, a syndrome, or by diagnostic criteria for a specific mental disorder. In addition, patients undergoing pharmacological treatments for medical illnesses are typically exposed to considerable psychosocial stress due to the suffering and disability associated with illness. These psychosocial factors may in themselves precipitate episodes of depression. Due to these complicating factors, sophisticated study designs are required to confirm an aetiological role for medications as risk factors for depression. Unfortunately, adequate studies have rarely been conducted, and much of the literature consists of case reports and clinical observations. Consequently, clinicians are frequently required to make clinical judgements about the aetiology of patients' depressive symptoms in the absence of definitive scientific information about the role of drugs. Nevertheless, a knowledge of the relevant literature will assist clinicians in making reasoned judgements about the aetiology, prevention and management of these disorders.

Abnormal behavioral responses to fenfluramine in patients with affective and personality disorders. Correlation with increased serotonergic responsivity

Serotonergic responsivity was assessed in 20 psychiatric patients by the prolactin response to a fenfluramine challenge test. During the fenfluramine challenge 6 of 20 patients (30%) spontaneously reported psychopathologic reactions that included: increased anxiety/agitation, psychotic symptoms, illusions, mood elevation, and anergia. The time of peak behavioral symptoms (2.5 +/- 0.8 hrs) corresponded closely to the time of peak increase in prolactin levels (3.0 +/- 1.1 hr). Abnormal behavioral responders had statistically significant greater increases in prolactin 1 to 4 hr after fenfluramine when compared to normal responders. Patients who developed an abnormal psychopathologic response to fenfluramine were characterized by higher levels of anxiety and agitation at the time of admission to the hospital but otherwise were not distinguishable on the basis of severity of other psychiatric symptoms. This study suggests that increased serotonergic transmission may trigger anxiety, psychosis, and mood elevation in specific vulnerable individuals, whereas other patients with similar psychiatric illnesses are not affected.

Can drugs cause depression? A review of the evidence

Drug-induced depressive disorders are classified in the DSM-III-R as organic mood syndrome, depressed type. The ability of certain drugs to cause depression is of clinical relevance because organic mood syndrome is a component of the differential diagnosis of depressive symptoms. Consequently, psychiatric textbooks often provide different lists of drugs thought to be capable of causing depression. Strong evidence supporting the existence of causal associations is often lacking. There is no specific drug for which there is definitive evidence of a causal association with depressive symptoms or depressive disorders. Nevertheless, for a number of drugs, the evidence is suggestive, although not conclusively, of a causal association. Despite this, rational decisions about the continuation or discontinuation of drugs can often be made. In this paper, the literature is reviewed and guidelines are suggested for the management of patients with depressive symptoms which may be related to drugs.

Assessment of sleep in hospital patients: a review of methods

Since sleep and healing appear to be associated, achieving the optimum quality of sleep among hospital patients should be a priority for both clinical nurses and researchers. This paper discusses various methods of sleep assessment which may be used by those intending to conduct research in this field.

Viloxazine, sleep, and subjective feelings

The sleep of eight volunteers (mean age 55) was recorded electrophysiologically while viloxazine 200 mg was taken daily for 3 weeks, preceded and followed by a week of matching blanks. The volunteers also made ratings of their feelings on visual analogue scales. Another 15 volunteers (mean age 34) took viloxazine 300 mg daily for 3 weeks, preceded and followed by 3 weeks of matching blanks, and they also made daily ratings of feelings. The drug diminished sleep duration and caused more frequent and longer transitions into wakefulness and drowsiness. Slow-wave sleep decreased and stage 2 increased. REM sleep was markedly reduced, especially initially, and there was a withdrawal rebound. Viloxazine impaired subjective concentration mood, and quality of sleep. Three volunteers, however, had striking mood elevation. The drug caused a small loss of weight, which correlated with gastrointestinal symptoms. Three older subjects experienced withdrawal vomiting and prostration. Viloxazine shares properties with imipramine and with amphetamines.

Anorectic drugs: use in general practice

The treatment of obesity is one of the major measures available today in the field of preventive medicine. In particular, the coronary epidemic of Western civilisation would be halted, and most cases of maturity-onset diabetes prevented, if obesity were to be treated effectively. Anorectic drugs act mainly on the satiety centre in the hypothalamus to produce anorexia. They also have various metabolic effects involving fat and carbohydrate metabolism, but many of these may be secondary to loss of weight. Most of the drugs are related directly or indirectly to amphetamine and in addition act by increasing general physical activity. Anorectic drugs tend to lose their effect after some months, and part of this reduction in effect may be due to chemical alterations produced by the drugs in the brain. All the drugs, with the exception of fenfluramine, have a stimulant effect on the central nervous system in some individuals, resulting in restlessness and nervousness, irritability and insomnia. Fenfluramine commonly produces drowsiness in normal doses, but has stimulant effects with overdosage. Dexamphetamine, phenmetrazine and benzphetamine all tend to cause euphoria and the risk of addiction is therefore considerable. Euphoria occasionally occurs with diethylpropion, phentermine and chlorphentermine, but to a much lesser extent. Side-effects also occur due to sympathetic stimulation and gastro-intestinal irritation. These side-effects may cause some individuals to stop taking the drug, but are never serious or dangerous. Drug interactions may occur with monoamine oxidase inhibitors and to a clinically unimportant extent, with antihypertensive drugs. The anorectic drugs have a very definite part to play in the treatment of obesity, mainly for those individuals who have altered their eating habits but have come to a plateau of weight which they find difficult to get below. The drugs are best given in a long-acting form and can safely be continued as long as weight loss persists, provided that the clinician exercises careful supervision. Dexamphetamine, phenmetrazine and benzphetamine should rarely be used because of the danger of addiction, and chlorphentermine is potentially hazardous for long-term use. Diethylpropion emerges as the drug of first choice, as fenfluramine has a tendency to cause depression and has a higher incidence of side-effects. Fenfluramine is mainly useful for people who are especially tense and for obese maturity-onset diabetics who have been unable to lose weight with the biguanides. Mazindol and phentermine appear to be useful as alternative drugs.

Fenfluramine: a review of its pharmacological properties and therapeutic efficacy in obesity

Fenfluramine has been used for a number of years as a short-term adjunct to diet in the management of obesity. Controlled studies and clinical experience have shown that it possesses anorectic activity at least as good as that of other therapeutically useful drugs of its type, but like these drugs it has only a limited role in the overall management of obesity. Tolerance to the anorectic effects of fenfluramine may possibly develop more slowly than to other chemically related drugs in patients with refractory obesity. The mechanism of its anorectic action is probably by an effect on the appetite control centres in the hypothalamus, rather than by an effect on glucose and lipid metabolism. However, its effect in enhancing glucose uptake into skeletal muscle may be of advantage in diabetes mellitus, preliminary studies suggesting that it is of potential use in maturity-onset obese diabetics who cannot be adequately controlled by dietary measures alone. The starting dosage in obesity of 40mg daily should be increased gradually over 2 to 4 weeks to 60 to 120mg. In general, little extra benefit is gained by higher dosage. When a course of therapy is to be discontinued, fenfluramine dosage should be reduced gradually over a period of 2 to 4 weeks in order to avoid mood depression which has occurred in some patients on abrupt withdrawal of the drug. With these recommendations, the majority of patients tolerate fenfluramine satisfactorily, although some patients may have to discontinue the drug because of troublesome gastro-intestinal problems, diarrhoea, drowsiness or dizziness. Unlike other amphetamine-derived anorectics, fenfluramine is not a central stimulant in therapeutic doses, and it probably has little abuse potential.

A study of the factors affecting the sleeping time following intracerebroventricular administration of pentobarbitone sodium: effect of prior administration of centrally active drugs

1 Injection of pentobarbitone sodium into a lateral cerebral ventricle of rats produced a loss of righting reflex. The duration of anaesthesia was dose-dependent.2 The optimum dose of pentobarbitone to allow study of the factors affecting the sleeping time was considered to be 650 mug injected in 25 mul water.3 In a study of the effect of age and sex on the sleeping time, the youngest rats used (88 g body weight) were found to be the most sensitive to barbiturate. Female rats were more sensitive than male animals.4 The duration of anaesthesia was not affected by induction or inhibition of hepatic drug-metabolizing enzyme activity.5 Prior administration (acute) of central nervous system depressant drugs shortened the latent period and prolonged the duration of sleep. Prior administration of stimulant drugs antagonized the effect of pentobarbitone.6 Animals withdrawn following chronic administration of a number of drugs, barbitone, barbitone/bemegride mixture, Mandrax (methaqualone: diphenhydramine; 10: 1), chlordiazepoxide, nitrazepam, chlorpromazine or ethanol, exhibited a significant tolerance to intracerebroventricularly administered pentobarbitone.7 Withdrawal of amphetamine, morphine, methyprylon or diazepam did not result in tolerance to intracerebroventricularly administered pentobarbitone.8 Chronic administration of all drugs except amphetamine and morphine induced a tolerance to intraperitoneally administered hexobarbitone (100 mg/kg).9 The usefulness of sleeping time determination following intracerebroventricular administration of pentobarbitone as an assessment of central nervous system excitability is discussed. It is concluded that this method gives a valid indication of the sensitivity of the central nervous system to barbiturate and of the level of excitability in general. The method is particularly applicable in situations where the activity of hepatic drug-metabolizing enzyme activity may be altered.

Withdrawal depression in obese patients after fenfluramine treatment

Measurements of subjective feeling in 20 patients receiving fenfluramine alternating with placebo and in 19 patients receiving phentermine alternating with placebo indicated that depression of mood occurred four days after fenfluramine withdrawal but no such depression was seen with phentermine.

On the slowness of action of tricyclic antidepressant drugs

It is widely believed that tricyclic antidepressants such as imipramine bring little benefit for ten days, that three or four weeks are needed to be sure, and that five or six weeks are needed to get the patient really back to health. Why should it take so long? Is it even true? If true it seems remarkable that such a challenge should have been largely ignored by theorists content to rest their arguments upon acute experiments with animals.

Chronic fenfluramine administration: some cerebral effects

Human cerebral function was monitored electrophysiologically during sleep over a period of months before, during, and after the intake of fenfluramine, 40-120 mg/day. Effects included dose-related reduction of paradoxical sleep, increase of intra-sleep restlessness, and changes in E.E.G. slow-wave sleep. It is hypothesized that weight loss may be associated with increase of the last. Grinding of teeth (bruxism) also was noted.Long-term studies make it possible to demonstrate changing central effects with time, including tolerance phenomena. Withdrawal abnormalities are related to the time taken for the drug to be eliminated-in the present case reaching a maximum four days after withdrawal.