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Concept: Serotonin syndrome


Clinical symptoms of acute 3,4-methylenedioxymethamphetamine (MDMA) intoxication and malignant hyperthermia have many similarities. At present, however, there is contradictory evidence concerning the malignant hyperthermia trigger potency of MDMA.

Concepts: Medical terms, Symptom, Hypothermia, Hyperthermia, Malignant hyperthermia, Serotonin syndrome


A series of C7-substituted chromone (1-benzopyran-4-one) derivatives were synthesized and evaluated as inhibitors of recombinant human monoamine oxidase (MAO) A and B. The chromones are structurally related to a series of C7-functionalized coumarin (1-benzopyran-2-one) derivatives which has been reported to act as potent MAO inhibitors. The results of the current study document that the chromones are highly potent reversible inhibitors of MAO-B with IC(50) values ranging from 0.008 to 0.370μM. While the chromone derivatives also exhibit affinities for MAO-A, with IC(50) values ranging from 0.495 to 8.03μM, they are selective for the MAO-B isoform. Structure-activity relationships (SAR) show that 7-benzyloxy substitution of chromone is suitable for MAO-B inhibition with tolerance for a variety of substituents and substitution patterns on the benzyloxy ring. It may be concluded that 7-benzyloxychromones are appropriate lead compounds for the design of reversible and selective MAO-B inhibitors. With the aid of modeling studies, potential binding orientations and interactions of selected chromone derivatives in the MAO-A and -B active sites are examined.

Concepts: Enzyme inhibitor, Antidepressant, Xanthine oxidase inhibitor, Monoamine oxidase, Monoamine oxidase inhibitor, Monoamine oxidase A, Serotonin syndrome, Phenethylamine


Adiponectin production during adipocyte differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) can be used to evaluate the pharmacological activity of anti-diabetic drugs to improve insulin sensitivity. Monoamine oxidase (MAO) inhibitors such as phenelzine and pargyline inhibit adipogenesis in murine pre-adipocytes. In this study, however, we found that selective MAO-A inhibitors, moclobemide and Ro41-1049, and a selective MAO-B inhibitor, selegiline, promoted adiponectin production during adipocyte differentiation in hBM-MSCs, which suggested the anti-diabetic potential of these drugs. In contrast, non-selective MAO inhibitors, phenelzine and tranylcypromine, inhibited adipocyte differentiation of hBM-MSCs. Concomitant treatments of MAO-A and MAO-B selective inhibitors did not change the stimulatory effect on adiponectin production in hBM-MSCs. Taken together, the opposite effects of isotype-selective MAO inhibitors on adiponectin production during adipogenesis in hBM-MSCs may not be directly associated with the inhibitory effects of MAO, suggested that the structure of MAO inhibitors may contain a novel anti-diabetic pharmacophore.

Concepts: Stem cell, Mesenchymal stem cell, Bone marrow, Xanthine oxidase inhibitor, Monoamine oxidase, Monoamine oxidase inhibitor, Serotonin syndrome, Monoamine oxidase inhibitors


Introduction: Monoamine oxidase (MAO) inhibitors, despite the initial pharmacological interest, are used in clinic for their antidepressant effect and in the management of Parkinson symptoms, due to the established neuroprotective action. Efficacy and tolerability emerged from large-scale and randomized clinical trials. Areas covered: Thirty-six patents range from April 2012 to September 2014. The number of chemotypes with inhibitory effects on MAO is truly high (40 synthetic compounds, 22 natural products and 6 plant extracts reported and licensed), and the present review is comprehensive of all compounds, which have been patented for their relevance to clinical medicine in this period range (27 patents). Moreover, some of the collected patents deal with new formulations of compounds endowed with MAO inhibitory properties (two patents) and new therapeutic options/drug associations for already known MAO inhibitors (seven patents). Expert opinion: The patents reported in this review showed that the interest in this field is constant and mainly devoted to the study of selective MAO-B inhibitors, used as drugs for the treatment of neurological disorders. The development of novel human MAO inhibitors took advantage of the discovery of new therapeutic targets (cancer, hair loss, muscle dystrophies, cocaine addiction and inflammation), the recognized role of MAOs as molecular biomarkers and their activity in other tissues.

Concepts: Pharmacology, Effectiveness, Neurology, Neurotransmitter, Monoamine oxidase, Patent, Monoamine oxidase inhibitor, Serotonin syndrome


The serotonin (5-hydroxtryptamine, 5-HT) system plays a role in analgesia and emesis. The aim of this study was to test whether opioids or ketamine inhibit the human 5-HT transporter and whether this increases free plasma 5-HT concentrations. HEK293 cells, stably transfected with the human 5-HT transporter cDNA, were incubated with morphine, hydromorphone, fentanyl, alfentanil, pethidine (meperidine), tramadol, ketamine, and the reference substance citalopram (specific 5-HT transporter inhibitor). The uptake of [(3)H]5-HT was measured by liquid scintillation counting. In a second series of experiments, study drugs were incubated with plasma of ten healthy blood donors and change of 5-HT plasma-concentrations were measured (ELISA). The end point was the inhibition of the 5-HT transporter by different analgesics either in HEK293 cells or in human platelets ex vivo. Tramadol, pethidine, and ketamine suppressed [(3)H]5-HT uptake dose-dependently with an IC50 of 1, 20.9, and 230 μM, respectively. These drugs also prevented 5-HT uptake in platelets with an increase in free plasma 5-HT. Free 5-HT concentrations in human plasma were increased by citalopram 1 μM, tramadol 20 μM, pethidine 30 μM, and ketamine 100 μM to 280 [248/312]%, 269 [188/349]%, and 149 [122/174]%, respectively, compared to controls without any co-incubation (means [95 % CI]; all p < 0.005). No change in both experimental settings was observed for the other opioids. Tramadol and pethidine inhibited the 5-HT transporter in HEK293 cells and platelets. This inhibition may contribute to serotonergic effects when these opioids are given in combination, e.g., with monoamine oxidase inhibitors or selective serotonin reuptake inhibitors.

Concepts: Opioid, Serotonin, Morphine, Analgesic, Selective serotonin reuptake inhibitor, Pethidine, Tramadol, Serotonin syndrome


In 2006, the US Food and Drug Administration (FDA) issued an advisory warning on the risk of serotonin syndrome with concomitant use of triptans and selective serotonin reuptake inhibitor (SSRI) or selective norepinephrine reuptake inhibitor (SNRI) antidepressants, but the true risk of serotonin syndrome in these patients remains unknown.

Concepts: Pharmacology, Serotonin, Antidepressant, Selective serotonin reuptake inhibitor, Tricyclic antidepressant, Norepinephrine reuptake inhibitor, Reuptake inhibitor, Serotonin syndrome


Studies establishing the use of new antidepressants often rely simply on proving efficacy of a new compound, comparing against placebo and single compound. The advent of large online databases in which patients themselves rate drugs allows for a new Big Data-driven approach to compare the efficacy and patient satisfaction with sample sizes exceeding previous studies. Exemplifying this approach with antidepressants, we show that patient satisfaction with a drug anticorrelates with its release date with high significance, across different online user-driven databases. This finding suggests that a systematic reevaluation of current, often patent-protected drugs compared to their older predecessors may be helpful, especially given that the efficacy of newer agents relative to older classes of antidepressants such as monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs) is as yet quantitatively unexplored.

Concepts: Illness, Antidepressant, Selective serotonin reuptake inhibitor, Monoamine oxidase, Tricyclic antidepressant, Monoamine oxidase inhibitor, Serotonin syndrome, Trimipramine


3,4-Methylenedioxymethamphetamine (MDMA, “ecstasy”) is a recreational club drug with supposed neurotoxic effects selectively on the serotonin system. MDMA users consistently exhibit memory dysfunction but there is an ongoing debate if these deficits are induced mainly by alterations in the prefrontal or mediotemporal cortex, especially the hippocampus. Thus, we investigated the relation of verbal memory deficits with alterations of regional cerebral brain glucose metabolism (rMRGlu) in recreational MDMA users.

Concepts: Brain, Cerebral cortex, Cerebrum, Hippocampus, Serotonin, Amphetamine, Psychedelic drug, Serotonin syndrome


MDMA (Ecstasy) is an illicit drug used by young adults at hot, crowed “rave” parties, yet the data on potential health hazards of its abuse remain controversial. Here, we examined the effect of MDMA on temperature homeostasis in male rats under standard laboratory conditions and under conditions that simulate drug use in humans. We chronically implanted thermocouple microsensors in the nucleus accumbens (a brain reward area), temporal muscle, and facial skin to measure temperature continuously from freely moving rats. While focusing on brain hyperthermia, temperature monitoring from the two peripheral locations allowed us to evaluate the physiological mechanisms (i.e., intracerebral heat production and heat loss via skin surfaces) that underlie MDMA-induced brain temperature responses. Our data confirm previous reports on high individual variability and relatively weak brain hyperthermic effects of MDMA under standard control conditions (quiet rest, 22-23°C), but demonstrate dramatic enhancements of drug-induced brain hyperthermia during social interaction (exposure to male conspecific) and in warm environments (29°C). Importantly, we identified peripheral vasoconstriction as a critical mechanism underlying the activity- and state-dependent potentiation of MDMA-induced brain hyperthermia. Through this mechanism, which prevents proper heat dissipation to the external environment, MDMA at a moderate nontoxic dose (9 mg/kg or ∼1/5 of LD50 in rats) can cause fatal hyperthermia under environmental conditions commonly encountered by humans. Our results demonstrate that doses of MDMA that are nontoxic under cool, quiet conditions can become highly dangerous under conditions that mimic recreational use of MDMA at rave parties or other hot, crowded venues.

Concepts: Physiology, Drug, Heat, Drug addiction, Techno, Amphetamine, Illegal drug trade, Serotonin syndrome


Serotonin syndrome is a toxic state, caused by serotonin (5HT) excess in the central nervous system. Serotonin syndrome’s main feature is neuro-muscular hyperexcitability, which in many cases is mild but in some cases can become life-threatening. The diagnosis of serotonin syndrome remains challenging since it can only be made on clinical grounds. Three diagnostic criteria systems, Sternbach, Radomski and Hunter classifications, are available. Here we test the validity of four assumptions that have become widely accepted: (1) The Hunter classification performs clinically better than the Sternbach and Radomski criteria; (2) in contrast to neuroleptic malignant syndrome, the onset of serotonin syndrome is usually rapid; (3) hyperthermia is a hallmark of severe serotonin syndrome; and (4) serotonin syndrome can readily be distinguished from neuroleptic malignant syndrome on clinical grounds and on the basis of medication history.

Concepts: Central nervous system, Nervous system, Brain, Diagnosis, Serotonin, Dopamine, Neuroleptic malignant syndrome, Serotonin syndrome