Possible development of the serotonin syndrome in man

Serotonin syndrome: a case of fatal SSRI/MAOI interaction

The author discusses a relatively new syndrome in which toxic hyperserotonergic states can result from the interaction of different classes of antidepressant drugs. He also distinguishes between this "serotonin syndrome" and neuroleptic malignant syndrome. Using case examples, he demonstrates the potential lethality of SS.

Newer aspects of the reversible inhibitor of MAO-A and serotonin reuptake, brofaromine

1. The reasons for developing second-generation MAOI are outlined. The expected advantage of reversibility as a safety valve with respect to tyramine potentiation is discussed. 2. Earlier data from in vitro and some ex vivo experiments had suggested an irreversible interaction of brofaromine with MAO-A, whereas the short duration of action, the absence of cumulation of effect and the displaceability by endogenously released substrates indicated reversibility. This apparent conflict could be solved by the demonstration that brofaromine behaves as a tight-binding reversible inhibitor. 3. In in vivo binding experiments with [3H]brofaromine given i.v., clorgyline, brofaromine and moclobemide were shown to dose-dependently displace the radioligand from MAO-A in the rat brain when administered after it. In corresponding experiments in the rat intestine in which the radioligand was administered p.o., similar results were obtained. Moreover, tyramine given orally in pressor doses after the radioligand also displaced it, confirming the idea that reversibility could act as a safety valve. 4. The evidence from animal and human experiments is presented that brofaromine is safer than classical MAO inhibitors with respect to tyramine potentiation. 5. Based on computer simulations, it is suggested that reduced liability of the new MAO reversible inhibitors to cause tyramine potentiation may potentially be linked to a reduced therapeutic efficacy. 6. The evidence is discussed that 5-HT uptake inhibition by brofaromine is relevant in its therapeutic effect in humans and may synergize with MAO-A inhibition, thus enhancing the impact of the latter on serotonergic transmission.

Fluoxetine: adverse effects and drug-drug interactions

This overview summarizes the major and minor side effects and drug interactions of fluoxetine. The adverse reactions include the "serotonin syndrome", cardiovascular complications, extrapyramidal side effects such as akathisia, dyskinesias, and parkinsonian-like syndromes and an apparently increased risk of suicidality. Fluoxetine-induced mania and hypomania, seizures and sexual disorders are evaluated along with minor symptoms of allergic reactions, stuttering, hematological changes, psoriasis, and inappropriate secretion of the antidiuretic hormone. The major fluoxetine-drug interactions involve the amino acids L-dopa and L-tryptophan, anorexiants, anticonvulsants, antidepressants, anxiolytics, calcium channel blockers, cyproheptadine, lithium salts, and drugs of abuse. The underlying mechanism and the paradoxical effects of fluoxetine are addressed.

Fluoxetine and suicidal behaviour. Some clinical and theoretical aspects of a controversy

“In the practical decisions of life it will scarcely ever be possible to go through all the arguments in favour of or against one possible decision, and one will therefore always have to act on insufficient evidence” Werner Heisenberg (1962).

The development of selective serotonin (5-hydroxytryptamine, 5-HT) reuptake inhibitors (SSRIs) has added a new dimension to the pharmacotherapy of depression. Their lack of sedative and anticholinergic effects together with relative safety in overdose, has led some authors to suggest that the older tricyclic antidepressants (TCAs) should not now be considered a first-line treatment (Montgomery, 1988). However, since a report by Teicher et al (1990) of suicidal preoccupation associated with fluoxetine treatment, there has been both intense media interest and animated correspondence in clinical and scientific journals (O'Donnell, 1991).

Mania associated with fluoxetine treatment in adolescents

Fluoxetine, a selective serotonin reuptake inhibitor, is gaining increased acceptance in the treatment of adolescent depression. Generally safe and well tolerated by adults, fluoxetine has been reported to induce mania. The cases of five depressed adolescents, 14-16 years of age, who developed mania during pharmacotherapy with fluoxetine, are reported here. Apparent risk factors for the development of mania or hypomania during fluoxetine pharmacotherapy in this population were the combination of attention-deficit hyperactivity disorder and affective instability; major depression with psychotic features; a family history of affective disorder, especially bipolar disorder; and a diagnosis of bipolar disorder. Further study is needed to determine the optimal dosage and to identify risk factors that increase individual vulnerability to fluoxetine induced mania in adolescents.

Fluoxetine-induced suicidality, serotonin, and seasonality

In spite of the complexities involved in suicide, fluoxetine has been prematurely and simplistically blamed for inducing this phenomenon. A variety of variables must be factored into such an interpretation. Nevertheless, given the complicated psychobiological circumstances involved, acute and rapid changes in serotonin (5-HT) function appear to be important to the understanding of changes in suicidal behavior. Such a mechanism may also explain the robust seasonal peak of suicides in spring.

The functional approach of biological research in psychiatry

When neurobiological investigation looks beyond nosological perspectives into the search for correlations between isolated symptoms or specific behaviour patterns (some of which may be normal) and laboratory findings, many controversies seem to become clear. A paradigm of this approach is the Serotonin (5-HT) involvement in a wide range of psychiatric disorders and specific behaviour patterns all of them characterized by a poor control of impulses. Psychopharmacotherapy with substances able to interfere with the metabolism of this neurotransmitter, mostly antidepressants, are able to compensate what appear to be very dissimilar conditions. Therefore, the hypothesis that Serotonin is important for the control of impulses is a key to the interpretation of many findings and to the penetration of the complex field of biological substrate of psycho (patho) logy.

Clomipramine: a tricyclic antidepressant effective in obsessive compulsive disorder

Clomipramine hydrochloride, a chlorinated analog of imipramine, is a widely used antidepressant recently approved for use in the U.S. for the treatment of obsessive-compulsive disorder (OCD), a potentially incapacitating affliction. Its primary pharmacologic action is blockade of the reuptake of the neurotransmitter serotonin. Its metabolite, desmethylclomipramine, is a potent norepinephrine reuptake inhibitor. Significant first-pass metabolism reduces oral bioavailability to less than 62 percent. The drug is widely distributed throughout the body (volume of distribution 9-25 L/kg) and is 90-98 percent protein-bound. Clomipramine follows first-order elimination pharmacokinetics, with a plasma half-life of 20-24 hours. Recent double-blind controlled clinical trials have demonstrated the drug's effectiveness in the treatment of OCD. Response is most often associated with doses greater than 75 mg/d, with 250 mg the maximum recommended daily dose. Relapse upon withdrawal is frequently reported. The adverse effect profile of clomipramine is similar to other tricyclic antidepressants, with anticholinergic, cardiovascular, sexual, and central nervous system effects the most prominent.

Clinical features, pathogenesis and management of drug-induced seizures

Many classes of pharmacological agents have been implicated in cases of drug-induced seizures. The list includes antidepressant drugs, lithium salts, neuroleptics, antihistamines (H1-receptor antagonists), anticonvulsants, central nervous system stimulants, general and local anaesthetics, antiarrhythmic drugs, narcotic and non-narcotic analgesics, non-steroidal anti-inflammatory drugs, antimicrobial agents, antifungal agents, antimalarial drugs, antineoplastic drugs, immunosuppressive drugs, radiological contrast agents and vaccines. For each of these classes of drugs, this article offers a revision of the literature and emphasises in particular the frequency of the adverse reaction, its clinical presentation, its presumed epileptogenic mechanism and the therapeutic strategy for the management of drug-induced seizures. An attempt is also made to distinguish seizures induced by standard dosages from those provoked by accidental or self-induced intoxication. For some classes of drugs such as antidepressants, neuroleptics, central nervous system stimulants (e.g. theophylline, cocaine, amphetamines) and beta-lactam antibiotics, seizures are a well recognised adverse reaction, and a large body of literature has been published discussing exhaustively the major aspects of the issue; sufficient data are available also for the other classes of pharmacological agents mentioned above. In contrast, several other drugs [e.g. allopurinol, digoxin, cimetidine, protirelin (thyrotrophin releasing hormone), bromocriptine, domperidone, insulin, fenformin, penicillamine, probenecid, verapamil, methyldopa] have not been studied thoroughly under this aspect, and the only source of information is the occasional case report. This review does not address the issue of seizures induced by drug withdrawal.

The proposed role of neurotransmitter receptors in the pathophysiology of human myoclonic disorders

The hypothesis that central neurotransmitter receptor abnormalities are the basis of human myoclonic disorders is novel. Receptor abnormalities in any of several different neurotransmitter systems implicated in myoclonus may be genetic or the consequence of various brain injuries. These abnormalities might define pharmacologic subgroups of possible relevance to the clinical, neurophysiologic, and pathologic heterogeneity of myoclonus. Receptor abnormalities may be the primary pathophysiologic defect, involving the surface recognition site or effector-transducer mechanisms in the defect, involving the surface recognition site or effector-transducer mechanisms in the post-synaptic cell. Alternatively, changes in receptor density or affinity may be adaptive (recovery of function) or maladaptive (supersensitivity, subsensitivity, dysregulation). Drug treatments, then, could be targeted at the receptor changes, reversing abnormalities and enhancing compensatory mechanisms. Current therapy may inadvertently have such an effect. Polytherapy may be justified to target more than one component of the "pharmacologic receptor". Identification of receptor abnormalities in human post-mortem brain may have diagnostic and therapeutic significance. New advances in the pharmacologic selectivity of receptor agonists and antagonists and in the measurement of receptors should be applied to the problem of myoclonus.

Serotonin in involuntary movement disorders

Several recent studies have emphasized that serotonergic pathways in the CNS are intimately involved in the modulation of motor behavior, and in the pathophysiology of human involuntary movement disorders. These observations are supported by recent reports demonstrating large serotonergic innervation of the striatum and substantia nigra, and a close interaction between the activity of serotonergic neurons with the dopamine system in the striatum and nigra. In the following communication we summarize evidence demonstrating defective serotonergic functions in a number of human movement disorders and discuss their management with serotonergic drugs.

Is monoamine oxidase inhibitor induced myoclonus serotoninergically mediated?

In the present study a single case observation of myoclonus during sleep-wave transition was monitored in a depressed patient treated with the monoamine oxidase inhibitor, phenelzine. The myoclonus had a rhythm of 1 c/second and lasted for two years, the duration of phenelzine treatment. Myoclonus appeared neither during wakefulness nor during sleep, but at wake-sleep-wake transitions. This "switch" myoclonus was associated with phasic muscle hyperactivity during REM sleep. Methysergide a 5-HT suppressor, decreased the switch myoclonus frequency and the REM muscle hyperactivity, indicating serotoninergic involvement in the mechanism of phenelzine induced myoclonus.

Myoclonus, hyperreflexia and diaphoresis in patients on phenelzine-tryptophan combination treatment

Three cases are presented on patients on an MAOI who developed a transient syndrome of myoclonus, hyperreflexia, jaw quivering, teeth chattering and diaphoresis after L-Tryptophan was added. Caution is advised when considering the addition of a serotonergic agent to MAOI's.

Effects of tranylcypromine treatment on neuroendocrine, behavioral, and autonomic responses to tryptophan in depressed patients

Effects of intravenous administration of the serotonin precursor tryptophan (TRP) on serum prolactin, neuromotor function, subjective mood, and blood pressure and pulse were determined in nine depressed patients before and during placebo-controlled treatment with the monoamine oxidase inhibitor (MAOI) tranylcypromine. Tranylcypromine significantly increased the prolactin response to TRP. Four patients developed a distinctive neuromotor syndrome following TRP during tranylcypromine, but not placebo, treatment. Symptoms included hyperreflexia, ankle clonus, nystagmus, incoordination, tremor, myoclonic jerks, and nausea. There were no differences in peak prolactin, mood, or autonomic responses between patients with and without the syndrome, but those with the syndrome had received active tranylcypromine for a significantly shorter duration. Tranylcypromine had little effect on TRP-induced changes in mood or autonomic function, except for a modest enhancement of the TRP-induced rise in diastolic blood pressure. These results suggest that tranylcypromine treatment may enhance serotonin function in depression.

Correlation of changes in alpha 2-adrenoceptor number and locomotor responses to clonidine following clorgyline discontinuation

[3H]-clonidine binding in vitro and the locomotor response to clonidine in vivo were studied over an eight week period following four weeks of treatment with the monoamine oxidase-inhibiting antidepressant, clorgyline (1 mg kg-1 day-1). Long-term clorgyline administration caused decreases in responsiveness to clonidine and in the number of alpha 2-adrenoceptors; these changes reverted towards pretreatment values very gradually over an eight week period following discontinuation of the drug. This study provides some of the first detailed evidence regarding the slow return of adaptional changes following discontinuation of an antidepressant drug in animals and has implications for understanding some delayed drug interactions associated with MAO-inhibiting antidepressants in man.