Increase in brain serotonin produced by bromocryptine

Treatment of four psychiatric emergencies in the intensive care unit

OBJECTIVES

To review the diagnosis and management of four selected psychiatric emergencies in the intensive care unit: agitated delirium, neuroleptic malignant syndrome, serotonin syndrome, and psychiatric medication overdose.

DATA SOURCES

Review of relevant medical literature.

DATA SYNTHESIS

Standardized screening for delirium should be routine. Agitated delirium should be managed with an antipsychotic and, possibly, dexmedetomidine in treatment-refractory cases. Delirium management should also include ensuring a calming environment and adequate pain control, minimizing benzodiazepines and anticholinergics, normalizing the sleep-wake cycle, providing sensory aids as required, and providing early physical and occupational therapy. Neuroleptic malignant syndrome should be treated by discontinuing dopamine blockers, providing supportive therapy, and possibly administering medications (benzodiazepines, dopamine agonists, and/or dantrolene) or electroconvulsive therapy, if indicated. Serotonin syndrome should be treated by discontinuing all serotonergic agents, providing supportive therapy, controlling agitation with benzodiazepines, and possibly administering serotonin2A antagonists. It is often unnecessary to restart psychiatric medications upon which a patient has overdosed in the intensive care unit, though withdrawal syndromes should be prevented, and communication with outpatient prescribers is vital.

CONCLUSIONS

Understanding the diagnosis and appropriate management of these four psychiatric emergencies is important to provide safe and effective care in the intensive care unit.

Triptans, serotonin agonists, and serotonin syndrome (serotonin toxicity): a review

The US Food and Drug Administration (FDA) have suggested that fatal serotonin syndrome (SS) is possible with selective serotonin reuptake inhibitors (SSRIs) and triptans: this warning affects millions of patients as these drugs are frequently given simultaneously. SS is a complex topic about which there is much misinformation. The misconception that 5-HT1A receptors can cause serious SS is still widely perpetuated, despite quality evidence that it is activation of the 5-HT2A receptor that is required for serious SS. This review considers SS involving serotonin agonists: ergotamine, lysergic acid diethylamide, bromocriptine, and buspirone, as well as triptans, and reviews the experimental foundation underpinning the latest understanding of SS. It is concluded that there is neither significant clinical evidence, nor theoretical reason, to entertain speculation about serious SS from triptans and SSRIs. The misunderstandings about SS exhibited by the FDA, and shared by the UK Medicines and Healthcare products Regulatory Agency (in relation to methylene blue), are an important issue with wide ramifications.

Drug-induced serotonin syndrome: a review

Serotonin syndrome, or serotonin toxicity (ST), is a clinical condition that occurs as a result of an iatrogenic drug-induced increase in intrasynaptic serotonin levels primarily resulting in activation of serotonin(2A) receptors in the central nervous system. The severity of symptoms spans a spectrum of toxicity that correlates with the intrasynaptic serotonin concentration. Although numerous drugs have been implicated in ST, life-threatening cases generally occur only when monoamine oxidase inhibitors are combined with either selective or nonselective serotonin re-uptake inhibitors. The triad of clinical features consists of neuromuscular hyperactivity, autonomic hyperactivity and altered mental status, which may present abruptly and progress rapidly. The awareness of ST is crucial not only in avoiding the unintentional lethal combination of therapeutic drugs but also in recognizing the clinical picture when it occurs so that treatment can be promptly initiated. In this review, the pathophysiology, clinical features, implicated drugs, diagnosis and treatment of ST are discussed.

The serotonin syndrome and its treatment

Serotonin syndrome is caused by drug induced excess of intrasynaptic 5-hydroxytryptamine. The clinical manifestations are mediated by the action of 5-hydroxytryptamine on various subtypes of serotonin receptors. There is no effective drug treatment established. The history of the treatment of serotonin syndrome with 5-hydroxytryptamine blocking drugs is reviewed. A literature search was undertaken using both Medline and a manual search of the older literature. Reports of cases treated with the 5-HT2 blockers cyproheptadine and chlorpromazine were identified and analysed. There is some evidence suggesting the efficacy of chlorpromazine and cyproheptadine in the treatment of serotonin syndrome. The evidence for cyproheptadine is less substantial, perhaps because the dose of cyproheptadine necessary to ensure blockade of brain 5-HT2 receptors is 20-30 mg, which is higher than that used in the cases reported to date (4-16 mg).

Freezing of gait in Parkinson's disease is improved by treatment with weak electromagnetic fields

Freezing, a symptom characterized by difficulty in the initiation and smooth pursuit of repetitive movements, is a unique and well known clinical feature of Parkinson's disease (PD). It usually occurs in patients with long duration and advanced stage of the disease and is a major cause of disability often resulting in falling. In PD patients freezing manifests most commonly as a sudden attack of immobility usually experienced during walking, attempts to turn while walking, or while approaching a destination. Less commonly it is expressed as arrest of speech or handwriting. The pathophysiology of Parkinsonian freezing, which is considered a distinct clinical feature independent of akinesia, is poorly understood and is believed to involve abnormalities in dopamine and norepinephrine neurotransmission in critical motor control areas including the frontal lobe, basal ganglia, locus coeruleus and spinal cord. In general, freezing is resistant to pharmacological therapy although in some patients reduction or increase in levodopa dose may improve this symptom. Three medicated PD patients exhibiting disabling episodes of freezing of gait are presented in whom brief, extracerebral applications of pulsed electromagnetic fields (EMFs) in the picotesla range improved freezing. Two patients had freezing both during "on" and "off" periods while the third patient experienced random episodes of freezing throughout the course of the day. The effect of each EMFs treatment lasted several days after which time freezing gradually reappeared, initially in association with "off" periods. These findings suggest that the neurochemical mechanisms underlying the development of freezing are sensitive to the effects of EMFs, which are believed to improve freezing primarily through the facilitation of serotonin (5-HT) neurotransmission at both junctional (synaptic) and nonjunctional neuronal target sites.

Antiparkinsonian dopamine agonists: a review of the pharmacokinetics and neuropharmacology in animals and humans

With the intention of compensating for the deficit of endogenous dopamine (DA) in the basal ganglia of Parkinsonian patients by substitution with agents which directly stimulate central DA receptors, synthetic DA agonists have been introduced almost 20 years ago for the symptomatic treatment of Parkinson's disease. The original expectation that DA agonists would be able to completely restore extrapyramidal motor function in Parkinsonian patients has turned out as too mechanistic and simplicative. However, undoubtedly DA agonists have improved therapeutic possibilities in Parkinson's disease. Thus, clinical evidence from controlled chronic studies in patients indicates that the therapeutic results following the early application of DA agonists in combination with L-DOPA on a long-term base are superior to the respective monotherapy. However, none of the DA agonists currently employed for antiparkinsonian treatment i.e. apomorphine and the ergoline derivatives bromocriptine, lisuride and pergolide, is optimal with respect to pharmacokinetic properties (poor oral bioavailability with considerable intra- and interindividual variation) or pharmacological profiles (low selectivity for DA receptors in case of the ergot agonists). The pathophysiology underlying Parkinson's disease which turned out more complex than initially expected might provide another explanation for the limited therapeutic potential of DA agonists. Therefore, apart from summarizing the pharmacokinetics, biotransformation, neuropharmacology and neurobiochemistry of the DA agonists employed clinically, the present article also reviews physiological aspects of (a) central dopaminergic neurotransmission including the topographical distribution of DA receptor subtypes and their functional significance, (b) the intracellular signal processing in striatal output neurons and (c) the intraneuronal mechanisms which integrate the various neurotransmitter signals converging on the striatal output neuron to a demand-adjusted effector cell response via the cross-talk between the different second messenger systems. Based on these considerations, potential pharmacological approaches for the development of improved antiparkinsonian drugs are outlined. There is a therapeutic demand for more selective and better bioavailable DA agonists. In particular, selective D-1 receptor agonists are highly desirable to provide a more specific probe than SKF 38 393 for clarifying the current controversy on the disparate findings in nonprimate species and monkeys or Parkinsonian patients, respectively, regarding the functional significance of D-1 receptors for the antiparkinsonian action of DA agonists or L-DOPA. The therapeutic importance of D-2 receptor activation is generally accepted; whether DA agonists combining a balanced affinity to both D-1 and D-2 receptors within one molecule (to some extent a property of apomorphine) might be superior to subtype-specific DA agonists remains to be tested clinically.(ABSTRACT TRUNCATED AT 400 WORDS)

Chronic treatment with bromocriptine induces behavioral supersensitivity in rats

Chronic treatment of rotating rats with equipotent doses of the dopamine (DA) agonists apomorphine (APO), 3-(3,4-dihydroxyphenyl)-1-n-propylpyrrolidine hydrobromide (DPPP) and bromocriptine (BRO) for four weeks resulted in marked differences in rotational activity following acute administration of these agonists. Whereas chronic treatment with APO and DPPP failed to produce any significant changes in agonist-induced rotational behavior, chronic BRO treatment induced a progressive increase in rotational activity up to a mean 200% increase over controls at four weeks. These findings may, in part, explain the long-term clinical efficacy of bromocriptine in patients with Parkinson's disease.

The lactation-blocking drug bromocriptine and its application to studies of weaning and behavioral development

An experimental method for blocking maternal lactation is reviewed and the possible application of this technique for experimentally manipulating weaning is considered. Maternal milk production can be inhibited using the prolactin-suppressing drug bromocriptine. The suitability of bromocriptine for use in behavioural experiments is considered. The pharmacology of bromocriptine (CB 154) is briefly outlined and a compilation of the reported lactation-inhibiting doses for various species is presented. The possible endocrine and behavioral side-effects and the toxicity of the drug are discussed. It is concluded that, in most species studied so far, the drug is relatively free from significant side-effects at the low doses needed to suppress lactation. Guidelines for the practical use of bromocriptine are suggested. Finally, some ideas about the possible application of the drug to the study of behavioral development and parent-offspring relationships are discussed.

Inhibition of neurotransmitter receptor binding by ergot derivatives

Bromocriptine, lergotrile, lisuride, metergoline, and the Sandoz ergot derivatives 25-397, 29-712, and 29-717 have been tested for their ability to inhibit the synaptic receptor binding of spiroperidol, 5-hydroxytryptamine (5-HT), d-lysergic acid diethylamide (LSD), quinuclidinyl benzilate (QNB), WB.4101, and gamma-aminobutyric acid (GABA). Only GABA binding was not affected, and QNB binding was decreased only by lergotrile and metergoline at high concentrations. The most potent inhibitors of the other ligands were bromocriptine and lisuride for spiroperidol (1-2 nMM), metergoline for 5-HT (29 nM), lisuride for LSD (15 nM), and lergotrile for WB.4101 (17 nM). The direct receptor effects of the ergot derivatives in vitro may contribute to understanding their in vivo effects on behavior and in predicting their therapeutic potential in neurological and neuroendocrine disorders.

Effects of ergot drugs on serotonergic function: behavior and neurochemistry

Several new ergot drugs were tested for behavioral and neurochemical effects related to serotonergic function. Lergotrile and bromocriptine potentiated the so-called "5-HT syndrome", a set of behaviours associated with increased serotonergic neurotransmission consequent to monoamine oxidase inhibition and tryptophan loading. Metergoline antagonized this behavior. In studies of receptor binding using 3H-5-HT or 3H-LSD, metergoline was the most potent at displacing specific ligand binding. Since the ergots also affect dopaminergic function, these results are discussed for their information on both dopaminergic and serotonergic actions of these drugs and their implications for clinical use of ergots.

Effects of morphine, physostigmine and raphe nuclei stimulation on 5-hydroxytryptamine release from the cerebral cortex of the cat

1. The release of 5-hydroxytryptamine (5-HT) from the cerebral cortex and caudate nucleus of brainstem-transected cats and from the cerebral cortex of rats anaesthetized with urethane was determined by radioenzymatic and biological assay. 2. The stimulation of nucleus linearis intermedius of raphe doubles the basal 5-HT release in the caudate nucleus and increases it 3 fold in the cerebral cortex. The effects of the electrical stimulation of the raphe are potentiated by chlorimipramine. 3. Brain 5-HT release is greatly increased by morphine hydrochloride (6 mg/kg i.v.) and by physostigmine (100 microgram/kg i.v.), but not by DL-DOPA (50 mg/kg i.v.). 4. It is suggested that the 5-HT releasing action of physostigmine can contribute to some of its pharmacological effects such as the analgesic effect so far attributed exclusively to its indirect cholinomimetic activity. 5. The 5-HT releasing action of physostigmine seems unrelated to its anticholinesterase activity.

Blockade of photically induced epilepsy by 'dopamine agonist' ergot alkaloids

The effect of the intravenous administration of ergot alkaloids on epileptic responses to intermittent photic stimulation )IPS) has been studied in adolescent baboons, Papio papio, from Senegal. Ergocornine, 1--2 mg/kg, produced marked autonomic and behavioural effects, slowed the EEG, and abolished myoclonic responses to IPS for 30--90 min. Ergometrine, 1 mg/kg, activated the EEG and blocked the induction of myoclonic responses for 1--3 h. Bromocriptine, 0.5--4 mg/kg, did not consistently prevent myoclonic responses to IPS. After pretreatment with a subconvulsant dose of allylglycine (180--200 mg/kg), lysergic acid diethylamide, 0.1 mg/kg, retained the capacity to block myoclonic responses to IPS, and ergocornine 1 mg/kg reduced such responses. The convulsant effect of allylglycine was enhanced, however, so that prolonged seizure sequences began 19--96 min after ergocornine administration. The protective action of ergot alkaloids against epileptic responses induced by sensory stimulation is interpreted in terms of effects at several sites, including dopaminergic and serotoninergic synapses.

The effect of bromocriptine on locomotor activity and cerebral catecholamines in rodents

The locomotor activity in mice induced by bromocriptine was suppressed by drugs inhibiting both dopaminergic and noradrenergic pre- and post-synaptic actions. The onset of locomotor activity was preceded by a period of decreased activity which lengthened with increasing dose. Both increased and decreased turnover of noradrenaline and decreased turnover of dopamine was shown by measurement of the dopamine metabolites homovanillic acid, dihydroxyphenylacetic acid (DOPAC) and the noradrenaline metabolite MOPEG-SO4 and following pretreatment of animals with α-methyl-p-tyrosine. The increased activity caused by bromocriptine did not correlate with a consistent biochemical change, but the period of behavioural suppression appeared to be associated with an increased noradrenaline turnover. Bromocriptine potently inhibited the noradrenaline-stimulated adenylate cyclase system from mouse limbic forebrain suggesting that the increased in vivo turnover of noradrenaline may be due to a post-synaptic receptor blockade. The involvement of cerebral dopamine receptors was substantiated by the ability of bromocriptine to displace [3H]haloperidol from binding sites in rat striatal preparations. The findings are interpreted as indicating a complex involvement of both noradrenaline and dopamine pre-and post-synaptic components in the locomotor activity produced by bromocriptine, possibly due to the involvement of a partial agonist action or an active metabolite.

The influence of bromocriptine on serotonin neurons

Bromocriptine (CB-154) is regarded as a dopamine agonist, hence is used in the treatment of Parkinson's disease. In the paper presented a possibility of the influence of bromocriptine on central serotonin neurons has been studied. It was demonstrated that CB-154, like tryptophan, 5-hydroxytryptophan, LSD or fenfluramine in previous experiments, potentiates the flexor reflex of the spinal rat, and this effect of CB-154 is prevented by serotonin antagonists--cryproheptadine and danitracen. CB-154, like fenfluramine used as a comparative serotonergic agent, rises the body temperature in rabbits. The hyperthermic effect of CB-154 is prevented by cyproheptadine, danitracen and mianserin. Haloperidol prevents the hyperthermia caused by a lower dose of CB-154 or on fenfluramine-induced hyperthermia. The results obtained indicate that CB-154, besides a dopaminomimetic action, possesses central serotonin actions as well.

Effects of nomifensine (HOE 984) upon psychomotor activity and intracranial self-stimulation in the rat

The effects of nomifensine maleate (HOE 984) were evaluated using two behavioral tasks. The drug produced dose related increases in both psychomotor activity and operant responding for brain stimulation reward. These results may point to possible psychostimulant properties for the drug.

Correlation of behavioural inhibition or excitation produced by bromocriptine with changes in brain catecholamine turnover

The dopamine agonist, bromocriptine, produced either inhibition or stimulation of motor behaviour in rats depending upon the dose and time after administration. Stimulation of motor activity occurred only with high doses after a 1-2 h delay. Both inhibition and stimulation were associated with decreased turnover of dopamine in the brain. Release of noradrenaline in brain and noradrenaline plus adrenaline in adrenal varied with motor activity. It is suggested that low doses of bromocriptine inhibit behaviour by activating an inhibitory presynaptic receptor, resulting in reduced synthesis and release of dopamine, whilst high doses cause behavioural excitation by activating the post-synaptic dopamine receptor.