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Biochemistry of Caffeine's Influence On Exercise Performance
Published in Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse, The Routledge Handbook on Biochemistry of Exercise, 2020
Jane Shearer, Robyn F. Madden, Jill A. Parnell
As previously mentioned, caffeine is a non-specific adenosine receptor antagonist. Adenosine receptors are a group of G protein–coupled receptors that mediate the physiological actions of adenosine. There are four main subtypes of adenosine receptors (A1, A2A, A2B, and A3) classified by their differential coupling to adenylyl cyclase that regulate cyclic AMP (cAMP) levels (26, 69). Receptors are distributed throughout the body, with different tissues expressing specific subtypes. Adenosine A1 and A3 receptors are coupled to Gi/o proteins, while adenosine A2A and A2B receptors act upon Gs/olf proteins (25, 69). Binding of adenosine to its receptors results in changes in cAMP levels that initiate a host of cell responses, including ion channels and enzymes. Caffeine has a similar structure to adenosine and therefore binds to the same receptors, essentially blocking the normal effects of adenosine (antagonist). However, caffeine has different affinities for each type of adenosine receptor, explaining why caffeine can produce distinct impacts on tissues depending on the type and level of adenosine receptors present (Table 24.1).
The Fight Against Cancer
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
Antibody-directed therapies take advantage of the unusual morphology of cancer cells, where the altered plasma membrane contains distinctive antigens, which are over expressed. These antigens are much more numerous on cancer cells than normal cells and monoclonal antibodies can be utilised as anti-cancer agents, with the desired mode of action being to activate the body’s immune system to direct killer cells towards the tumour. The antibody can also act as a receptor antagonist.
Synthetic Endotoxin Antagonists
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Daniel P. Rossignol, Lynn D. Hawkins, William j. Christ, Seiichi Kobayashi, Tsutomu Kawata, Melvyn Lynn, Isao Yamatsu, Yoshito Kishi
The central role that lipid A plays in activating cells makes it clear that blocking the cellular “receptor” for lipid A may halt the chain of events leading to systemic inflammatory response and septic shock. A pharmacological receptor antagonist is often best derived from modification of the parent agonistic molecule. For this reason, we have modified lipid A from a variety of bacterial species as lipid A (and LPS) antagonists. Lipid A from E. coli is the toxic principle of the LPS molecule, first isolated by Westphal and Luderitz (6-disaccharide of D-glucosamine as well as phosphates at the anomeric (0–1) and 0–4’ positions (see Fig. 5).
Association between anticholinergic medication uses and the risk of pneumonia in elderly adults: a meta-analysis and systematic review
Published in Annals of Medicine, 2023
Mindan Wu, Zhixuan Li, Wenchuan Zheng, Jia Zhuang, Shuhan Wu, Qipeng Zhou, Junfu Cai, Houzhen Zheng, Guixing Zeng, Weilin Zhang, Shengbin Zhang, Maohuang Lin, Xianyang Zhong, Qichuan Zhang
Recently, more and more attention has been paid to whether medication uses contributes to the higher risk of pneumonia in elderly people, except for the known risk factors. Anticholinergic drugs are frequently prescribed to the elderly adults. Anticholinergic medication includes drugs from a wide range of therapeutic categories which are used in a variety of diseases. Drugs with anticholinergic properties account for 23% of the ambulatory patients and nearly 60% of nursing home residents. They nonselective act on muscarinic receptor antagonist and thus cause many side effects centrally and peripherally. Pharmacokinetic and pharmacodynamic properties are changing related with age, therefore the older patients are more susceptible to anticholinergic drugs. Therefore, the American Geriatric Society 2019 have defined some anticholinergic drugs as inappropriate medications and should be avoided in elderly patients [4].
Current and emerging pharmacotherapeutic strategies for Tourette syndrome
Published in Expert Opinion on Pharmacotherapy, 2022
There are a few recent studies on emerging treatments for TS that modulate histaminergic, noradrenergic, and serotonergic pathways [33]. A trial investigating atomoxetine, a noradrenaline reuptake inhibitor which might improve response inhibition parameters in patients with TS, has been registered. An H3-receptor antagonist called AZD5213 has been assessed for safety and tolerability in patients with TS, however it has not shown any significant difference compared to placebo. Pimavanserin is a serotonin receptor inverse agonist (without dopamine receptor antagonist properties) which is approved for the treatment of Parkinson’s disease psychosis. The results of a recent open-label phase 1 pilot study to evaluate pimavanserin in the treatment of motor and behavioral symptoms in adults with TS were encouraging and warranted further research by larger, placebo-controlled, trials [92]. Of note, the adverse effects of pimavanserin were reported to be common but not severe (headache, bloating, dizziness, drowsiness, nausea, and dysgeusia. A significant degree of tic reduction was demonstrated when D-cycloserine, an antibiotic with learning enhancing properties, was administered to patients with TS undergoing habit reversal training (as compared to patients treated with habit reversal training and placebo) [93]. A follow-up study of D-cycloserine augmented habit reversal training for youth with tic disorders has been registered.
Blinding and expectancy confounds in psychedelic randomized controlled trials
Published in Expert Review of Clinical Pharmacology, 2021
Suresh D. Muthukumaraswamy, Anna Forsyth, Thomas Lumley
Similar to the parallel groups design, but here active treatment is preceded by a pharmacological antagonist (Figure 2g). For example, the opioid receptor antagonist naltrexone has been found to block the antidepressant effects of ketamine [137]. Similarly, lamotrogine blocks some of ketamine’s psychedelic properties [138,139]. For classical psychedelics, the 5HT2A receptor antagonist ketanserin has been shown to block the psychological effects of both LSD and psilocybin in a dose dependent manner – with 20 mg ketanserin leading to partial blockade and 40 mg near complete blockade [140,141]. In a recent dose-response crossover design study of LSD, healthy participants were given LSD doses of 25 μg, 50 μg, 100 μg or 200 μg or 200 μg with ketanserin (40 mg) [142]. Participants were asked to retrospectively identify these conditions – after each session and at the end of the study. Accuracy was generally high, indicating de-masking although notably the +ketanserin condition was most commonly mistaken for 50/25 μg of LSD.