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Antihistamines
Published in Sarah H. Wakelin, Howard I. Maibach, Clive B. Archer, Handbook of Systemic Drug Treatment in Dermatology, 2015
Tabi A. Leslie, Clive E. Grattan
Acting on H1 receptors in the skin, histamine induces vasodilation, increased vascular permeability, itching and smooth muscle contraction as well as in the respiratory and gastrointestinal (GI) tracts. All H1 antihistamines reversibly act on H1 receptors as inverse agonists. Some of the sedating (first-generation) antihistamines have additional antimuscarinic, antiadrenergic, antiserotonergic antagonizing or local anaesthetic effects.
Anticholinergic and Neuroleptic Drugs
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
As noted earlier, the SSRIs have a higher therapeutic ratio than TCAs, and O.D. due solely to SSRIs is rare. Yet, the more serious of the acute toxic reactions, either idiosyncratic or due to excessive quantities, are the serotonin syndrome and development of seizures. Treatments for these conditions are similar and approached as with O.D. from TCAs. Cardiac monitoring, administration of activated charcoal (1 g/kg orally), and sodium bicarbonate (used for electrocardiogram QRS prolongation) are featured modalities. Patients should be observed for complications, focusing particularly on cardiac integrity and vital signs, for at least 6 h post ingestion. In addition, the serotonin syndrome is managed with cyproheptadine, an antihistaminic drug used as an antiserotonergic agent in this situation. A dose of 4 to 8 mg orally is repeated every 2 h until a favorable response is noted, followed by 4 mg orally every 6 h for 48 h. Necessarily, all other antidepressants are discontinued, and supportive care is optimized. Benzodiazepines, such as diazepam, are used to relieve muscle rigidity and pain. Discontinuation syndrome is managed primarily by avoiding abrupt discontinuation or withdrawal of the medication. The serotonin syndrome, as well as complications and adverse reactions resulting from interactions with other drugs of similar classes, can be avoided by incorporating a wash-out period of at least 1 to 2 weeks. Because of the SSRIs’ long half-life, this practice of using a wash-out period prevents possible competition of the different classes for the same metabolic enzymes, thus alleviating unpredictable shifts in drug plasma concentrations.
Focussing on the fundaments – assessing and treating Clozapine Induced Gastrointestinal Hypomotility
Published in International Journal of Psychiatry in Clinical Practice, 2020
Graham Blackman, Adisha Kapila, Charlotte Maria Grosskopf, Luiz Dratcu
Clozapine has been demonstrated to be the most effective antipsychotic in treatment-resistant schizophrenia (Meltzer 1992); however, it is also recognised as having several serious and potentially fatal side-effects. These include haematological and cardiac complications, such as agranulocytosis (Alvir et al. 1993) and myocarditis (Haas et al. 2007) necessitating close monitoring with blood tests and electrocardiograms. Relative to these, Clozapine Induced Gastrointestinal Hypomotility (CIGH) has gained little attention despite affecting an estimated 80% of patients (Citrome et al. 2016; Every-Palmer et al. 2016) and being identified as the commonest cause of clozapine-related death (Ellis et al. 2006). Early clinical features of CIGH include constipation, vomiting, nausea and paradoxical diarrhoea (Flanagan and Ball 2011), with progression to paralytic ileus, obstruction and, in severe cases, bowel perforation (Levin et al. 2002; Hibbard et al. 2009). The cause of CIGH remains to be fully elicited, yet anticholinergic, antiadrenergic and antiserotonergic effects of clozapine are thought to play an important role, with risk factors including older age, male gender and higher daily dose of clozapine (West et al. 2017). Inpatients are at particularly high risk due to their limited mobility and severity of mental illness.
Can therapeutic strategies prevent and manage dyskinesia in Parkinson’s disease? An update
Published in Expert Opinion on Drug Safety, 2019
Valentina Leta, Peter Jenner, K. Ray Chaudhuri, Angelo Antonini
The atypical neuroleptic, clozapine, is an antidopaminergic, antiserotonergic, antimuscarinic, antiadrenergic, and antihistaminergic agent. It is an efficacious anti-dyskinetic drug according to a single randomized double-blind, placebo-controlled study (N = 50). Indeed, Clozapine 39.4 ± 4.5 (SEM) mg/day significantly reduced the duration of ‘on’ periods with LID at 10 weeks as assessed by patient diary compared with placebo [156]. Although the drop-out rate was higher for the placebo than the active group (14% versus 10%) and no agranulocytosis was observed in the active group, the potential risk of serious adverse events limits the use of clozapine in clinical practice.
Making sleep easier: pharmacological interventions for insomnia
Published in Expert Opinion on Pharmacotherapy, 2018
Lukas Frase, Christoph Nissen, Dieter Riemann, Kai Spiegelhalder
Pharmacological interventions targeting the ARAS could in theory include substances with inhibiting properties in either of the mentioned neurotransmitter systems. In fact, some of the most commonly used non-hypnotic sleep medications have been identified by demonstrating sedating side effects. Available medication includes anticholinergic, antihistaminergic, antidopaminergic, antiserotonergic, and antinoradrenergic substances, e.g. sedating antidepressants, antipsychotics, or antihistamines. The most novel substances, so called dual orexin receptor antagonists, decrease orexinergic transmission thereby diminishing wakefulness [23].