Clinical features and treatment of overdosage of monoamine oxidase inhibitors and their interaction with other psychotropic drugs

Phenelzine (monoamine oxidase inhibitor) increases production of nitric oxide and proinflammatory cytokines via the NF-κB pathway in lipopolysaccharide-activated microglia cells

Phenelzine is a potent monoamine oxidase inhibitor that is used in patients with depression. It is also well known that nitric oxide (NO) synthase inhibitors show preclinical antidepressant-like properties, which suggests that NO is involved in the pathogenesis of depression. The purpose of this study was to determine if phenelzine affects the production of NO and tumor necrosis factor-alpha (TNF-α) in activated microglia cells. BV-2 microglia cells and primary microglia cells were cultured in DMEM and DMEM/F12 and then cells were treated with LPS or LPS plus phenelzine for 24 h. The culture medium was collected for determination of NO, TNF-α, and IL-6 and cells were harvested by lysis buffer for Western blot analysis. Phenelzine increased the lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS), as well as the release of TNF-α and IL-6 in BV-2 microglia cells. It is also confirmed that phenelzine increased the levels of NO, TNF-α and IL-6 in LPS-activated primary microglia cells. Phenelzine increased nuclear translocation of NF-κB by phosphorylation of IκB-α in LPS-activated microglia cells. These findings suggest that high doses of phenelzine could aggravate inflammatory responses in microglia cells that are mediated by NO and TNF-α.

Emergency management of hypertension in children

Systemic arterial hypertension in children has traditionally been thought to be secondary in origin. Increased incidence of risk factors like obesity, sedentary life-styles, and faulty dietary habits has led to increased prevalence of the primary arterial hypertension (PAH), particularly in adolescent age children. PAH has become a global epidemic worldwide imposing huge economic constraint on health care. Sudden acute increase in systolic and diastolic blood pressure can lead to hypertensive crisis. While it generally pertains to secondary hypertension, occurrence of hypertensive crisis in PAH is however rare in children. Hypertensive crisis has been further subclassified depending on presence or absence of end-organ damage into hypertensive emergency or urgency. Both hypertensive emergencies and urgencies are known to cause significant morbidity and mortality. Increasing awareness among the physicians, targeted at investigation of the pathophysiology of hypertension and its complications, better screening methods, generation, and implementation of novel treatment modalities will impact overall outcomes. In this paper, we discuss the etiology, pathogenesis, and management of hypertensive crisis in children. An extensive database search using keywords was done to obtain the information.

The development of a whole-cell based medium throughput screening system for the discovery of human aldosterone synthase (CYP11B2) inhibitors: old drugs disclose new applications for the therapy of congestive heart failure, myocardial fibrosis and hypertension

Cytochrome P450 enzymes play an important role in steroid hormone biosynthesis of the human adrenal gland, e.g., the production of cortisol and aldosterone. Aldosterone, the most important human mineralocorticoid, is involved in the regulation of the salt and water homeostasis of the body and thus in the regulation of blood pressure, whereas cortisol is the most important glucocorticoid of the human body. CYP11B-dependent steroid hydroxylases are drug development targets, and since they are very closely related enzymes, the discovery of selective inhibitors has been subject to intense investigations for several years. Here we report the development of a whole-cell medium throughput screening technology for the discovery of CYP11B2 inhibitors. The new screening system displayed high reproducibility and was applied to investigate a library of pharmacologically active compounds. 1268 compounds were investigated during this study which revealed 5 selective inhibitors of CYP11B2 (after validation against CYP11B1). The new inhibitors of CYP11B2 are already existing drugs that could be used either in the treatment of hyperaldosteronism-related diseases or as lead compounds that could further be optimised to achieve safer and selective inhibitors of aldosterone synthase. Article from the Special issue on 'Targeted Inhibitors'.

Acute myocarditis after massive phenelzine overdose

BACKGROUND

Monoamine oxidase inhibitors (MAOIs) are uncommonly used due to their high frequency of adverse effects, including tachycardia and hypertension. Recently, there has been renewed interest in the role of this class of drugs in treating a variety of psychiatric disorders. The clinical features of MAOI overdose are poorly characterised. This paper describes a novel cardiac complication of phenelzine toxicity in a previously healthy young adult with no history of cardiovascular disease.

METHODS

A 23-year-old woman presented to hospital after massive phenelzine overdose, and the clinical features and pathological findings are discussed in light of existing literature.

RESULTS

Clinical features of phenelzine toxicity included reduced consciousness level, seizures, and tachycardia, in keeping with previous reports. Unexpectedly, the patient developed severe and unexplained hypotension and impaired left ventricular function, and died 3 days after initial presentation. Post-mortem examination confirmed high serum phenelzine concentrations (4.1 mg/L) and histopathological features that were consistent with drug-induced acute myocarditis.

CONCLUSION

Acute myocarditis was attributed to phenelzine in the absence of any plausible alternative explanation. This possible complication should be considered in patients who develop unexplained hypotension after phenelzine overdose.

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).

Serotonin syndrome: history and risk

This review focuses on the history of investigations into the behavioural reaction resulting from excess stimulation of post-synaptic 5-hydroxytryptamine receptors and the relative risk of this occurring with different combinations of drugs. Other aspects, particularly treatment with 5-hydroxytryptamine receptor antagonists, are reviewed in a recent separate paper [44]. The first human case was in 1955 and animal work had defined the characteristic features by 1958, and established they were lessened by chlorpromazine. Substantial evidence of a 'dose-effect' relationship existed by 1984. The relative risk with different drug combinations is assessed from available evidence and argued to be strongly associated with the degree of elevation of 5-hydroxytryptamine, which is greatest following combinations of irreversible inhibitors of monoamine oxidase A and B with potent serotonin reuptake inhibitors. The various serotonergic drugs that may be implicated in serotonin syndrome are tabulated and discussed in relation to the relative risk. It is suggested that the proposed 'diagnostic criteria' for serotonin syndrome are inappropriate since there is a continuous spectrum from side effects to toxicity. The term 'serotonin syndrome' may encourage the presumption that it is an idiosyncratic response, as neuroleptic malignant syndrome is usually considered to be. The terms 'toxic serotomimetic reaction' or 'toxic serotonin syndrome' may be preferable alternatives. The differences between serotonin syndrome and neuroleptic malignant syndrome are highlighted with examples from difficult or questionable cases in the recent literature. It is proposed that more systematic national collection of toxicity data is essential in order to quantify the relative risk of serotonin syndrome with various combinations of serotonergic drugs.

Dangerous monoamine oxidase inhibitor interactions are still occurring in the 1990s

The clinical course is described of a 28-year-old woman who was severely ill following ingestion of a Do-Do tablet (which consists of ephedrine, caffeine and theophylline), 24 h after discontinuing phenelzine treatment. Signs and symptoms were delayed for 8 h after which she developed encephalopathy, neuromuscular irritability, hypotension, sinus tachycardia, rhabdomyolysis and hyperthermia. Her illness was complicated by pneumonia and adult respiratory distress syndrome (ARDS). The management of monoamine oxidase inhibitor (MAOI) toxicity, which can arise from interactions and overdoses, is discussed. It should be remembered that, despite the increase in use of alternative and safer antidepressants, MAOI interactions still occur and unless they are managed appropriately, are potentially fatal. Patients need to be warned that restrictions apply for up to 2 weeks after stopping the medication, and doctors need to be aware that serious interactions can occur in this time period.

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.

Phenelzine poisoning

A 46-year-old female with severe phenelzine poisoning was managed successfully by alpha blockade and fluid loading, with the aid of invasive haemodynamic monitoring. The pathophysiology was documented, showing elevated plasma and urinary catecholamines, cardiovascular abnormalities and a contracted blood volume. Most of these changes were reversed following treatment.

Monoamine oxidase inhibitor overdose

Described is the clinical course of a 26-year-old woman who died following an overdose of the MAO inhibitor phenelzine. Signs and symptoms of toxicity were delayed in onset. Initial findings of excessive neuromuscular activity were followed by severe hyperthermia, coma, cardiovascular collapse, acute renal failure, hemolysis, rhabdomyolysis, and disseminated intravascular coagulation. A review of the literature suggests that these features are not unusual following MAO inhibitor overdosage. The pathophysiology and management of MAO inhibitor poisoning are discussed.

Tranylcypromine ('Parnate') overdose: measurement of tranylcypromine concentrations and MAO inhibitory activity and identification of amphetamines in plasma

A case of tranylcypromine overdose is reported. Tranylcypromine, amphetamine methamphetamine and phenylethylamine were detected in the plasma by gas chromatography and their identity confirmed by mass spectrometry. The data suggested that the amphetamines were metabolic products of tranylcypromine. Platelet monoamine oxidase activity was more than 95% inhibited during the 72 h after the overdose despite complete clinical recovery by that time. The possible role of amphetamines and phenylethylamine in causing the clinical manifestations of tranylcypromine overdose is discussed.

A study of refractory cases of depressive illnesses and their response to combined antidepressant treatment

Opinions differ on the effectiveness and the risk involved in treating depressive illnesses with combinations of monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants. Some authorities, including the Food and Drug Administration in the United States, the former Witts Committee in this country, and the pharmaceutical firms producing antidepressants, have given serious warnings against combining MAOIs with tricyclic antidepressants. These warnings have been repeated more recently by Beck (1967), Malitz (1966) and Shepherd et al. (1968).