Chronic fenfluramine administration: some cerebral effects

Sleep deprivation and energy metabolism: to sleep, perchance to eat?

PURPOSE OF REVIEW

Many people currently sleep only 5-6 h per night. Epidemiological studies have demonstrated that self-reported short sleep is associated with an increased incidence of obesity and diabetes, highlighting the importance of this trend for public health. This finding has triggered renewed research into the mechanisms that link the regulation of mammalian sleep and metabolism.

RECENT FINDINGS

In rodents, periods of starvation are accompanied by increased vigilance and sleep loss, presumably to help maximize food finding and energetic survival, whereas sleep deprivation results in increased energy expenditure and weight loss, consistent with a role of sleep in energy conservation and tissue maintenance. Information about the corresponding processes in humans is limited. Available data indicate that despite the presence of qualitative and quantitative differences, human sleep and metabolism also share reciprocal connections.

SUMMARY

Evolution in an environment with limited resources has established bidirectional links between sleep and energy homeostasis, the molecular mechanisms of which are emerging rapidly. Epidemiological data suggest that the unique ability of humans to restrict their sleep voluntarily in an environment that promotes physical inactivity and overeating may have a negative impact on metabolic health. Randomized intervention trials are needed to confirm the validity of this hypothesis.

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.

Effect of fenfluramine on episodic ACTH and cortisol secretion

OBJECTIVE

The central serotoninergic system is known to modulate the activity of the hypothalamic-pituitary-adrenal axis, but the effect of fenfluramine, a serotonin reuptake inhibitor, on ACTH and cortisol secretion is not well understood. We have therefore evaluated its effects on the hypothalamic-pituitary-adrenal axis in healthy controls.

DESIGN

Episodic secretion of ACTH and cortisol was investigated in 6 healthy volunteers under basal conditions and again during treatment with 20 and 60 mg fenfluramine given orally every 8 hours. On all occasions blood samples were obtained at 10-minute intervals for 24 hours and the mode of hormone secretion was analysed by three different methods (PULSAR, CLUSTER, DESADE). In addition ACTH and cortisol responses to CRH were tested at the end of the sampling period.

RESULTS

At the lower dose fenfluramine had no effect on ACTH and cortisol secretion. At the higher dose a significant increase of mean plasma ACTH (+85%) and cortisol (+129%) levels as well as of urinary free cortisol secretion (+44%) was observed. Fenfluramine did not modulate the frequency, but increased the amplitudes of ACTH and cortisol secretory episodes. ACTH and cortisol responses to CRH injection remained unchanged. Maximum plasma levels of d-fenfluramine and d-norfenfluramine were documented 2-4 hours after the ingestion of the drug.

CONCLUSION

Fenfluramine stimulates the activity of the hypothalamic-pituitary-adrenal axis at a suprapituitary level by modulating the amplitude of ACTH and cortisol secretory bursts.

The effects of fenfluramine on sleep and prolactin in depressed inpatients: a comparison of potential indices of brain serotonergic responsivity

The effects of fenfluramine, an indirect serotonergic agonist, on electroencephalographic sleep and prolactin secretion were assessed in 12 unmedicated inpatients with a primary diagnosis of major depressive episode. Compared to prefenfluramine profiles, sleep studies performed following fenfluramine administration showed a statistically significant reduction of slow-wave sleep (SWS) (p < 0.001) and a corresponding increase in percentage of stage-2 sleep (p < 0.007). Automated delta wave counts per min decreased significantly during the first nonrapid eye movement (NREM) period (p = 0.04), and automated rapid-eye movement (REM) counts were also decreased in the second REM period (p = 0.02). These effects on sleep electroencephalogram (EEG) did not correlate significantly with another measure of serotonergic responsivity, namely peak prolactin level following fenfluramine, nor with the severity of depression. The reductions in SWS and REM counts are proposed to be the result of time-dependent changes in serotonergic neurotransmission following the administration of fenfluramine. These findings are consistent with earlier work suggesting a role for serotonin in initiation and regulation of SWS and REM sleep.

Effect of dexfenfluramine on sleep in healthy subjects

The acute effects of dexfenfluramine on nocturnal sleep were studied in ten healthy male subjects by means of sleep EEG recordings and ratings of subjective sleep quality. Four different dosages (3 mg, 7 mg, 15 mg, and 30 mg) were tested, administered over a period of 3 days each. Under 15 mg and 30 mg dexfenfluramine, only slight effects on sleep were observed: 15 mg led to decreased sleep efficiency in the first night of medication, and to reduced percentage of slow wave sleep in the first and third night. A significant lengthening of REM latency was present in the third night under 30 mg dexfenfluramine, without changes in other REM sleep parameters. Daily doses of 3 mg and 7 mg dexfenfluramine did not influence sleep, except for a significant REM latency reduction observed in the first night under 3 mg. Apart from a transient slight impairment under 30 mg, ratings of subjective sleep quality did not mirror any impact of dexfenfluramine. The data suggest that therapeutic dosages of dexfenfluramine only slightly influence nocturnal sleep, which contrasts with the known impact of other anti-obesity agents like the amphetamines. Unlike classical antidepressants, dexfenfluramine does not reduce REM sleep; in light of a hypothetical link between REM sleep reduction and antidepressant action of a drug, dexfenfluramine is not expected to have a pronounced antidepressant effect.

The effects of an occlusal splint on the electromyographic activities of the temporal and masseter muscles during maximal clenching in patients with a habit of nocturnal bruxism and signs and symptoms of craniomandibular disorders

The effects of a full arch maxillary plane occlusal splint on the level of electromyographic (EMG) activity in the anterior temporal and masseter muscles during maximal clenching were studied in 31 patients with a habit of nocturnal bruxism and signs and symptoms of craniomandibular disorders, before and after occlusal splint therapy. The results showed, before treatment, that the occlusal splint changed significantly (in 71% of patients) the level of EMG activity during maximal clenching. However, these changes were not consistent and differed between patients and even, in some patients, between muscles. After long-term occlusal splint therapy and improvement of the signs and symptoms of craniomandibular disorders, the number of patients who had an identical level of EMG activity during maximal clenching in the intercuspal position and on the occlusal splint tended to increase. Moreover, in these patients the level of symmetry of action in pairs of muscles during maximal clenching was strong, and the splint did not change this level of symmetry.

Effects of paroxetine on human sleep

In a first double-blind, balanced order study, 12 subjects, mean age 57 years, took placebos at bedtime on 2 nights, paroxetine 15 mg on 2 nights and paroxetine 30 mg on 2 nights. In a second study, 12 subjects, mean age 56 years, took placebos on 2 mornings and paroxetine 30 mg on 2 mornings. Electrophysiological measures of all-night sleep were made on each night subsequent to medication. Paroxetine caused more frequent awakenings, reduced total sleep and strongly suppressed REM sleep, especially the 30 mg dosage. When it had been taken in the morning, paroxetine additionally delayed sleep onset and increased slow-wave sleep.

A clinical and electromyographic study of the long-term effects of an occlusal splint on the temporal and masseter muscles in patients with functional disorders and nocturnal bruxism

The postural activity of the temporal and masseter muscles in thirty-one patients with signs and symptoms of functional disorders were studied: before, during and after 3-6 months of occlusal splint therapy. The fluctuating signs and symptoms, as well as the postural activity of the temporal and masseter muscles were significantly reduced after treatment. Further, the coefficients of correlation within pairs of postural activity of the right and left muscles increased significantly. After cessation of the splint therapy the signs and symptoms recurred to the pre-treatment level within 1-4 weeks in about 80% of the patients. The results indicate that an occlusal splint can eliminate or diminish signs and symptoms of functional disorders and re-establish symmetric and reduced postural activity in the temporal and masseter muscles, which can facilitate procedures, such as functional analysis and occlusal adjustment.

Experimental neurotoxicity of the anorectic fenfluramine. I. A fine structural model for cerebral lysosomal storage and neuroglial reaction

Fenfluramine, an amphophilic compound which is a halogenated derivative of amphetamine, is still used as an anorectic agent for weight reduction, as it acts on the satiety center of the hypothalamus. Holtzman strain rats aged 6 days were daily injected s.c. fenfluramine hydrochloride at the dose of 75 mg/kg body weight. The animals were killed at different time intervals between days 7 and 40, and different parts of the brain were examined by light and electron microscopy. About half of the animals showed intralysosomal membrano-cytoplasmic bodies in the oligodendroglia, neurons, and neuropil, maximally in the animals receiving 8-19 injections. They were seen as concentrically arranged, single-layered lamellae; small dense bodies; or larger heterogeneous bodies. The mechanism of production of such inclusions could be the formation of complexes of this amphophilic compound with tissue phospholipids, or some enzyme-inhibiting action. A marked prominence of dark cells, predominantly oligodendroglia, was also noticed in the brains of experimental animals. Some of these cells appeared to be dark neurons, probably resulting from the serotonin-depleting effect of fenfluramine. A few dark cells were identified as resting microglial cells, while macrophagic "reactive microglia" were detected in the brains of very young animals. Fenfluramine appears to provide a model for studying neuroglial reactions.

Drug-induced psychiatric disorders

This article is a review of the principal drug-induced psychiatric symptoms that are likely to be encountered in daily clinical practice as a result of drug abuse, overdoses or side effects of drugs prescribed for treatment. Many categories of medication have the potential to produce psychiatric symptoms, but antitubercular drugs, hypotensive agents and steroids have the highest incidence in clinical practice. Additionally, the problems of alcohol are all too frequently overlooked. The variety and frequency of secondary psychiatric symptoms which may be drug-related emphasise the importance of a careful consideration of all drugs taken by a patient with psychiatric complaints, to determine causal association with symptoms.

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.

The anorectic and hypotensive effect of fenfluramine in obesity

A trial is reported of the hypotensive and anorectic effect of fenfluramine in general practice when combined with Yudkin's modification of the Marriott diet. The results confirm the anorectic effect and show that the maximum reduction of blood pressure occurs during the first four weeks of treatment.

Dreaming, fenfluramine, and vitamin C

The effect of increasing doses of fenfluramine on dream patterns was studied in 20 patients receiving a reducing diet with or without a controlled dietary intake of vitamin C daily. The dream pattern was unchanged in six patients and dreams disappeared in another who normally dreamed often. In 13 patients dreams increased in frequency and intensity, and in five the dreams assumed frightening proportions. There was a significant straight-line relation between response and the size of the dose. When placebo tablets were given to four patients their dreams disappeared or assumed their pretreatment normal pattern. Absence of vitamin C from the diet did not significantly affect the dream pattern. That fenfluramine has dose-related cerebral effects should be remembered in patients with a history of mental illness.

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.

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.

Drugs of dependence though not of abuse: fenfluramine and imipramine

Measures of subjective feeling used by five patients indicated that depression of mood occurred about four days after fenfluramine withdrawal. An experiment in which another 11 patients took fenfluramine 80 mg for 28 days confirmed the depression, maximal on the fourth withdrawal day. It also indicated that in the first week of administration there was some mood elevation, but with feelings of impaired ability to concentrate. The drug reduced appetite and weight. A comparison is drawn with imipramine, which was found to induce initial and withdrawal changes of subjective experience (of dreaming) in six volunteers. It is suggested that certain mood-influencing drugs may not be drugs of abuse because of some unpleasant initial effects, though they can be drugs of dependence.