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Cholinergic Antagonists
Published in Sahab Uddin, Rashid Mamunur, Advances in Neuropharmacology, 2020
Vishal S. Gulecha, Manoj S. Mahajan, Aman Upaganlawar, Abdulla Sherikar, Chandrashekhar Upasani
Various physiological studies were carried out to show bronchodilator activity of anticholinergic agents. Bronchodialation is controlled by the cholinergic (parasympathetic) division of the autonomic nervous system (ANS) (Widdicombe, 1979; Nadel, 1980). In this research, the drugs, such as ipratropium, were approved as a bronchodilator by inhalation route as it lacks systemic effects (Brunton et al., 2011). The objectives of the present chapter are to represent the pharmacological aspects of muscarinic antagonist and related drugs. Further, the therapeutic benefits of ganglionic blockers and neuromuscular blocking drugs are discussed.
Antagonists at Muscarinic Cholinergic Receptors
Published in Kenneth J. Broadley, Autonomic Pharmacology, 2017
The changes in heart rate induced by atropine are not usually accompanied by alterations in blood pressure or cardiac output because there is adequate compensatory reflex adjustment. Atropine and hyoscine have little effect upon blood pressure or the calibre of blood vessels since they are under no significant parasympathetic tone. Those blood vessels that receive a sympathetic cholinergic innervation in skeletal muscle (see Chapter 1) do not appear to have a major role in the control of vascular tone and therefore clinical doses of atropine are similarly ineffective. Larger doses approaching toxic levels, however, cause an anomalous peripheral vasodilatation and fall in blood pressure. Cutaneous blood vessels, particularly in blush areas, are dilated to produce a profound flushing of the skin. The mechanism for this remains obscure, but it is unrelated to muscarinic receptor blockade and is not produced by other muscarinic antagonists. It may be due to a direct vasodilator action or related to the inhibition of sweating that accompanies atropine administration and compensation for the consequent increase in skin temperature. The latter, however, would be expected to occur with other M3 antagonists. The dry flushed skin is a characteristic sign of belladonna poisoning, together with the rapid but weak pulse.
A randomized trial comparing physostigmine vs lorazepam for treatment of antimuscarinic (anticholinergic) toxidrome
Published in Clinical Toxicology, 2021
George Sam Wang, Keith Baker, Patrick Ng, Gregory C. Janis, Jan Leonard, Rakesh D. Mistry, Kennon Heard
Overdose of antimuscarinic xenobiotics, such as antihistamines, is a common scenario in medical toxicology. In 2018, the American Association of Poison Control Centers’ National Poison Data System (NPDS) reported 14,139 antihistamine ingestion, which had the third greatest rate increase in exposures over the past 10 years, at a mean of 1,018 (CI 934, 1102) per year [1]. In addition to antihistamines, several medications and natural products are competitive muscarinic antagonists, including antipsychotics and plants such as Datura stramonium (Jimson Weed) [2,3]. The result of antagonizing muscarinic receptors is a constellation of signs and symptoms (toxidrome) which can consist of mydriasis, decreased sweat, decreased bowel sounds, agitation, delirium, hallucinations, urinary retention, tachycardia, flushed skin and seizures [2,3].
Tiotropium in asthma – perspectives for the primary care physician
Published in Postgraduate Medicine, 2021
Asthma management involves a control-based cycle of assessing symptoms, adjusting treatment, and reviewing response [1]. Building on a base of inhaled corticosteroids (ICS), either alone or in combination with long-acting beta2-agonists (LABAs) as preferred controller options, the Global Initiative for Asthma (GINA) strategy document outlines a stepwise pharmacological approach to achieve good symptom control and to minimize future risk of exacerbations [1]. Besides increasing the dose of ICS+LABA, using additional controller options may be helpful for the management of asthma [1]. However, these controller options (leukotriene receptor antagonists [LTRAs] and theophylline) are often limited by their reduced efficacy and risk of side effects compared with ICS [3,4], the need for phenotype assessment (biologics) [1], and systemic side effects (oral corticosteroids [OCS]) [1]. Long-acting muscarinic antagonists (LAMAs) have been successfully used in the management of chronic obstructive pulmonary disease (COPD) for many years. Treatment with LAMA alone or as part of dual or triple therapy with LABA or LABA+ICS, respectively, is recommended by the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines [5]. The need for new treatment options for managing patients with asthma led to the use of long-acting muscarinic LAMAs [1,6], which have traditionally been used in the management of COPD [5].
Cognitive and mood side effects of lower urinary tract medication
Published in Expert Opinion on Drug Safety, 2019
A. Elif Muderrisoglu, Klaus F. Becher, Stephan Madersbacher, Martin C. Michel
Adverse effects of muscarinic antagonists as a class are highly plausible mechanistically based on the known function of muscarinic receptors in the CNS [45–47]. Whether such effects occur in a given patient treated with a given drug appears to depend on three factors: the vulnerability of the patients as indicated by permeability of his/her blood-brain-barrier [5] and/or cognitive baseline state; the CNS penetration of the drug [49]; and the subtype-selectivity of the drug. Thus, adverse effects on CNS function can in principle occur with any muscarinic antagonist with oral formulations of oxybutynin apparently having the greatest risk. The only muscarinic antagonist apparently free of that risk is trospium. The latter conclusion is not only based on specific clinical studies [16,19,20,44] but also on the concept that trospium as a quarternary amine does not pass the blood-brain-barrier. The latter has been confirmed in a dedicated study in which oral treatment of elderly volunteers with therapeutic doses of trospium did not result in detectable drug levels in the CNS [50]. These data make trospium the muscarinic antagonist with the smallest potential to disturb CNS function; however, the very same property of being a quarternary amine also causes a limited and highly variable bioavailability [89], which makes prediction of drug exposure in target tissue difficult.