{"id":45614,"date":"2019-08-02T21:17:27","date_gmt":"2019-08-02T20:17:27","guid":{"rendered":"http:\/\/localhost\/wordpress\/?page_id=929"},"modified":"2019-09-16T08:58:25","modified_gmt":"2019-09-16T08:58:25","slug":"agonists-antagonists-and-drug-toxicity","status":"publish","type":"page","link":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/","title":{"rendered":"Agonists, Antagonists and Drug Toxicity"},"content":{"rendered":"\n
\n

A\/Prof. Ken Rodgers School of Life Sciences<\/h1>\n<\/div><\/div>\n\n\n\n
<\/div>\n\n\n\n

Contents<\/strong><\/p>\n\n\n\n

\n

What are agonists and antagonists?<\/a><\/p>\n\n\n\n

Affinity vs efficacy<\/a><\/p>\n\n\n\n

Partial agonists and spare receptors<\/a><\/p>\n\n\n\n

Types of receptor antagonism<\/a><\/p>\n\n\n\n

Desensitization and tachyphylaxis<\/a><\/p>\n\n\n\n

Drug toxicity<\/a><\/p>\n<\/div><\/div>\n\n\n\n

References<\/h2>\n\n\n\n
  • Rang HP, Dale MM, Ritter JM, Flower RJ, Henderson, G (2016) Pharmacology<\/em>, 8th Edition, Churchill Livingstone, Sydney.<\/li>
  • How drugs act: general principles\u2013 Section 1, part 2<\/li><\/ul>\n\n\n\n
    <\/div>\n\n\n\n
    \n

    What are Agonists and Antagonists?<\/h1>\n<\/div><\/div>\n\n\n\n

    What is an agonist?<\/h2>\n\n\n\n
    • Drug, hormone, toxin, autacoid or neurotransmitter that elicits a biological effect when it interacts with receptors \u2013 bethanechol<\/strong> (used for urinary retention) combines with muscarinic ACh receptor<\/li>
    • Bethanechol<\/strong>mimics action of ACh (the neurotransmitter at these receptors)<\/li>
    • Magnitude of signal depends on number of receptors occupied and\/or rate of formation of drug-receptor complexes<\/li>
    • Signal amplified by intracellular mechanism<\/li><\/ul>\n\n\n\n
      • \"\"<\/figure><\/li>
      • \"\"<\/figure><\/li>
      • \"\"<\/figure><\/li>
      • \"\"<\/figure><\/li><\/ul>\n\n\n\n
        <\/div>\n\n\n\n
        • \"\"<\/figure><\/li>
        • \"\"<\/figure><\/li>
        • \"\"<\/figure><\/li><\/ul>\n\n\n\n
          <\/div>\n\n\n\n

          What is an antagonist?<\/h2>\n\n\n\n

          A drug which interacts with a receptor, does not elicit a biological effect and blocks or reverses the effect of an agonist <\/p>\n\n\n\n

          • \"\"<\/figure><\/li>
          • \"\"<\/figure><\/li><\/ul>\n\n\n\n
            <\/div>\n\n\n\n
            • \"\"<\/figure><\/li>
            • \"\"<\/figure><\/li>
            • \"\"<\/figure><\/li><\/ul>\n\n\n\n
              <\/div>\n\n\n\n
              \n

              Agonist v antagonist<\/strong><\/p>\n\n\n\n

              \"\"<\/p>\n\n\n\n

              <\/p>\n<\/div><\/div>\n\n\n\n

              <\/div>\n\n\n\n
              \n

              Affinity vs efficacy<\/h1>\n<\/div><\/div>\n\n\n\n

              Other definitions 1<\/h2>\n\n\n\n
              • What is affinity?<\/strong>
                • Relative tendency of a drug to combine with its receptor<\/li><\/ul><\/li>
                • What is intrinsic activity or efficacy?<\/strong>
                  • Capacity of a drug to produce a pharmacological effect after binding to its receptor ie the maximal possible effect than can be produced by the drug (Emax<\/sub>)<\/li><\/ul><\/li>
                  • Agonists possess?<\/strong>
                    • Affinity and intrinsic activity<\/li><\/ul><\/li>
                    • Antagonists possess?<\/strong>
                      • Affinity but lack intrinsic activity<\/li><\/ul><\/li><\/ul>\n\n\n\n
                        <\/div>\n\n\n\n
                        \"\"<\/figure>
                        \n

                        Affinity<\/h2>\n\n\n\n
                        • The response of the cell is a product of affinity and efficacy (intrinsic activity)<\/li><\/ul>\n\n\n\n
                          • Drug A fits the receptor better than Drug B<\/li>
                          • Drug A has a greater affinity for this receptor than Drug B<\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                            <\/div>\n\n\n\n
                            \"\"<\/figure>
                            \n

                            Intrinsic activity\/efficacy<\/h2>\n\n\n\n
                            • The response of the cell is due to affinity and <\/strong>intrinsic activity<\/strong><\/li>
                            • Drug C <\/strong>has a greater <\/strong>intrinsic activity<\/strong> at this receptor than <\/strong>Drug A<\/strong><\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                              <\/div>\n\n\n\n
                              \n

                              Partial agonists and spare receptors<\/h1>\n<\/div><\/div>\n\n\n\n
                              \"\"<\/figure>
                              \n

                              Other definitions 2<\/h2>\n\n\n\n
                              • Partial agonist<\/strong>
                                • Compound which interacts with a receptor but produces less than the maximum effect \u2013 less intrinsic activity or efficacy. Even with 100% receptor binding it does not produce a maximal response.<\/li>
                                • Eg. buprenorphine<\/strong> (partial agonist at \u00b5 opioid receptor) produces less analgesia than morphine<\/strong> (full agonist)<\/li><\/ul><\/li>
                                • Spare receptors<\/strong>
                                  • Implied, when the maximum effect is produced with less than 100% receptor occupancy. Requires functional as well as binding studies.<\/li><\/ul><\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                                    <\/div>\n\n\n\n
                                    \n

                                    Biased agonism<\/p>\n\n\n\n

                                    Two agonists bind at the same site on the receptor yet the red agonist is better at evoking response 1 and the green agonist is better at evoking response 2.<\/p>\n\n\n\n

                                    \"\"<\/p>\n<\/div><\/div>\n\n\n\n

                                    <\/div>\n\n\n\n
                                    \n

                                    Types of receptor antagonism<\/h1>\n<\/div><\/div>\n\n\n\n

                                    Type of receptor antagonism<\/h2>\n\n\n\n
                                    • Competitive<\/strong>
                                      • Compete for the binding site
                                        • Reversible<\/li>
                                        • Irreversible<\/li><\/ul><\/li><\/ul><\/li>
                                        • Non-competitive (Allosteric modulation)<\/strong>
                                          • Bind elsewhere eg. Ion channel blockers<\/li><\/ul><\/li><\/ul>\n\n\n\n
                                            • \"\"<\/figure><\/li>
                                            • \"\"<\/figure><\/li>
                                            • \"\"<\/figure><\/li><\/ul>\n\n\n\n
                                              <\/div>\n\n\n\n
                                              \"\"<\/figure>
                                              \n

                                              Types of antagonism 1<\/h2>\n\n\n\n
                                              • Reversible competitive <\/strong>antagonist<\/strong>
                                                • Agonist competes with antagonist for same receptor<\/li>
                                                • \uf0c7 [antagonist] progressively inhibits the agonist response<\/li>
                                                • Parallel shift of dose response (DR)-curve to the right and ED50<\/sub> is altered<\/li>
                                                • But blockade CAN be reversed by a higher dose of agonist<\/li>
                                                • ie the same Emax<\/sub> is reached
                                                  • eg atropine<\/strong> (muscarinic receptor antagonist<\/em>)<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                                                    • \"\"<\/figure><\/li>
                                                    • \"\"<\/figure><\/li>
                                                    • \"\"<\/figure><\/li><\/ul>\n\n\n\n
                                                      <\/div>\n\n\n\n
                                                      \"\"<\/figure>
                                                      \n

                                                      Types of antagonism 1<\/h2>\n\n\n\n
                                                      • Reversible competitive <\/strong>antagonist<\/strong>
                                                        • Agonist competes with antagonist for same receptor.<\/li>
                                                        • Parallel shift of DR-curve to the right and ED50<\/sub> is altered.<\/li>
                                                        • But blockade CAN be reversed by a higher dose of agonist.<\/li>
                                                        • The same Emax<\/sub> is reached
                                                          • eg atropine<\/strong> (muscarinic receptor antagonist<\/em>)<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n<\/div><\/div>\n\n\n\n

                                                            Types of antagonism 3<\/h2>\n\n\n\n
                                                            • Irreversible competitive<\/strong> antagonist<\/strong>
                                                              • Antagonist binds at same site.<\/strong><\/li>
                                                              • Antagonist dissociates slowly, or not <\/strong>at all, from the receptors \u2013 irreversible bond (eg covalent bond)<\/li>
                                                              • No change in the antagonist occupancy takes place when the agonist is applied.<\/li>
                                                              • Thus blockade CANNOT be reversed by higher dose of agonist<\/li>
                                                              • Prevent agonists from producing any effect \u2013 Emax<\/sub> is \uf0c8 but the agonist acts normally at the unoccupied receptors<\/li>
                                                              • Thus no shift in DR-Curve ie. no change in ED50<\/sub> for agonist
                                                                • eg. methysergide<\/strong> (5-HT receptor antagonist<\/em>) used in Rx<\/sub> of migraine<\/li>
                                                                • eg. \u03b1-neurotoxins<\/strong> from snake venom (nicotinic receptor antagonist<\/em>)<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n\n
                                                                  <\/div>\n\n\n\n

                                                                  Types of antagonism 4<\/h2>\n\n\n\n
                                                                  • \"\"<\/figure><\/li>
                                                                  • \"\"<\/figure><\/li><\/ul>\n\n\n\n
                                                                    <\/div>\n\n\n\n
                                                                    \"\"<\/figure>
                                                                    \n

                                                                    Types of antagonism 3 <\/h2>\n\n\n\n
                                                                    • Irreversible competitive antagonist<\/strong>
                                                                      • Antagonist dissociates slowly, or not at all, from the receptors \u2013 irreversible bond (eg covalent bond)<\/li>
                                                                      • No change in the antagonist occupancy takes place when the agonist is applied<\/li>
                                                                      • Thus blockade CANNOT be reversed by higher dose of agonist<\/li>
                                                                      • Prevent agonists from producing any effect \u2013 Emax<\/sub> is \uf0c8 but the agonist acts normally at the unoccupied receptors<\/li>
                                                                      • Thus no shift in DR-Curve ie. no change in ED50<\/sub> for agonist
                                                                        • eg. methysergide<\/strong> (5-HT receptor antagonist<\/em>) used in Rx<\/sub> of migraine<\/li>
                                                                        • eg. \u03b1-neurotoxins<\/strong> from snake venom (nicotinic receptor antagonist<\/em>)<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                                                                          <\/div>\n\n\n\n

                                                                          Types of antagonism 5<\/h2>\n\n\n\n
                                                                          • Non-competitive antagonism or allosteric modulation of receptor function<\/strong>
                                                                            • Bind at a site close to but distinct from the agonist receptor site<\/li>
                                                                            • Only have an effect on receptors that are activated<\/li>
                                                                            • May be an ion channel or G-protein linked to the receptor ie block in receptor-effector linkage since it acts at different site
                                                                              • Eg. suxamethonium<\/strong>(depolarising muscle relaxant)desensitises nicotinic receptor ion channel<\/li>
                                                                              • Eg. calcium antagonists <\/em>(eg verapamil<\/strong> and nifedipine<\/strong>) non-specific block of contractions by other drugs<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n\n

                                                                                Types of antagonism 6<\/h2>\n\n\n\n
                                                                                \"non-comp<\/figure><\/div>\n\n\n\n
                                                                                \"\"<\/figure>
                                                                                \n

                                                                                Types of antagonism 7<\/h2>\n\n\n\n
                                                                                • Physiological Antagonism<\/strong>
                                                                                  • Blockade of an effect due to production of an effect in the opposite direction (acts via separate cells or separate physiological systems or opposing receptors)<\/li>
                                                                                  • Eg. In gut \u2013 ACh contraction mediated through muscarinic receptor antagonised by noradrenaline (Nad) relaxation mediated through beta receptor<\/li><\/ul><\/li>
                                                                                  • Weak partial agonists can also seem to be like competitive antagonists<\/li>
                                                                                  • If receptors are constitutively active the addition of a weak agonist can actually decrease receptor activation these are known as \u2018inverse agonists\u2019<\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                                                                                    <\/div>\n\n\n\n
                                                                                    \n

                                                                                    Desensitization and tachyphylaxis<\/h1>\n<\/div><\/div>\n\n\n\n

                                                                                    Desensitization and tachyphylaxis 1<\/h2>\n\n\n\n
                                                                                    • Synonymous terms \u2013 a drug effect which gradually diminishes over a few seconds to minutes<\/li><\/ul>\n\n\n\n
                                                                                      • Causes<\/strong>
                                                                                        • Change in receptors
                                                                                          • Receptor resulting in tight binding of agonist without opening of ion channel<\/li><\/ul><\/li>
                                                                                          • Exhaustion of mediators
                                                                                            • Depletion of neurotransmitters or second messengers<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n\n
                                                                                              <\/div>\n\n\n\n

                                                                                              Tolerance (days or weeks to develop)<\/h2>\n\n\n\n
                                                                                              • Causes<\/strong>
                                                                                                • Increased metabolic degradation
                                                                                                  • Induction of metabolic enzymes eg barbiturates\/ethanol in liver<\/li><\/ul><\/li>
                                                                                                  • Physiological adaptation
                                                                                                    • Eg. side effects (nausea, sleepiness) sometimes tend to subside<\/li><\/ul><\/li>
                                                                                                    • Translocation of receptors (hours)
                                                                                                      • Receptors may be internalised by endocytosis and degraded in lysosomes eg. gonadotrophin-releasing hormone inhibits gonadotrophin release by continuous receptor stimulation (usually pulsatile) used in prostatic cancer.<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n\n
                                                                                                        <\/div>\n\n\n\n
                                                                                                        \n

                                                                                                        Drug Toxicity<\/h1>\n<\/div><\/div>\n\n\n\n
                                                                                                        \"\"<\/figure>
                                                                                                        \n

                                                                                                        Drug toxicity 1<\/h2>\n\n\n\n
                                                                                                        • \u201cAll things are poisons, nothing is without poisonous qualities. It is only the dose which makes a thing a poison<\/em>\u201d<\/li><\/ul>\n\n\n\n

                                                                                                          Paraphrased from Paracelsus (1493-1541)<\/p>\n\n\n\n

                                                                                                          • Potency provides little information about the dose of drug at which toxic effects manifest themselves<\/li>
                                                                                                          • Determined from the LD50<\/sub> (median lethal dose)
                                                                                                            • Dose of drug that is lethal to 50% of subjects<\/li><\/ul><\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                                                                                                              \"\"<\/figure>
                                                                                                              \n

                                                                                                              Drug Toxicity 2<\/h2>\n\n\n\n
                                                                                                              • Thus therapeutic index (LD50<\/sup>\/ED50<\/sub>) gives an idea of the relative margin of safety of a drug<\/li>
                                                                                                              • Greater this ratio the safer the drug
                                                                                                                • Must be >1.0 to be therapeutic agent, <2.0 typically see toxicity at therapeutic dose<\/li><\/ul><\/li>
                                                                                                                • Therapeutic index:
                                                                                                                  • Digoxin<\/strong> (Rx<\/sub> heart failure)= 1.5-2.0, vs.<\/li>
                                                                                                                  • Penicillin<\/strong> (antibiotic) >100 (non-allergic patients)<\/li><\/ul><\/li><\/ul>\n<\/div><\/div>\n\n\n\n
                                                                                                                    \n

                                                                                                                    \"\"<\/p>\n<\/div><\/div>\n\n\n\n

                                                                                                                    Drug Toxicity 2<\/h2>\n\n\n\n
                                                                                                                    • Thus therapeutic index (LD50<\/sup>\/ED50<\/sub>) gives an idea of the relative margin of safety of a drug<\/li>
                                                                                                                    • Greater this ratio the safer the drug and must be >1.0 to be therapeutic agent, <2.0 typically see toxicity at therapeutic dose<\/li>
                                                                                                                    • Therapeutic index:
                                                                                                                      • Digoxin<\/strong> (Rx<\/sub> heart failure) = 1.5-2.0, vs.<\/li>
                                                                                                                      • Penicillin<\/strong> (antibiotic) >100 (non-allergic patients)<\/li><\/ul><\/li>
                                                                                                                      • Depends on therapeutic use \u2013 certain situations (eg. anaesthesia) may require higher dose of drugs than other situations (eg. sedation, sleep)<\/li>
                                                                                                                      • Since the ED50<\/sub> goes up while the LD50<\/sub> remains unchanged, the therapeutic index goes down (ie greater risk of toxicity)<\/li><\/ul>\n\n\n\n
                                                                                                                        <\/div>\n\n\n\n

                                                                                                                        Therapeutic Index<\/h2>\n\n\n\n
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li>
                                                                                                                        • \"\"<\/figure><\/li><\/ul>\n\n\n\n
                                                                                                                          <\/div>\n\n\n\n
                                                                                                                          \n

                                                                                                                          Drug targets: receptors<\/p>\n\n\n\n

                                                                                                                          \"\"<\/p>\n<\/div><\/div>\n\n\n\n

                                                                                                                          \n

                                                                                                                          Drug targets: enzymes<\/p>\n\n\n\n

                                                                                                                          \"\"<\/p>\n<\/div><\/div>\n\n\n\n

                                                                                                                          \n

                                                                                                                          Drug targets: enzymes<\/p>\n\n\n\n

                                                                                                                          \"\"<\/p>\n<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"

                                                                                                                          Contents References Rang HP, Dale MM, Ritter JM, Flower RJ, Henderson, G (2016) Pharmacology, 8th Edition, Churchill Livingstone, Sydney. How drugs act: general principles\u2013 Section 1, part 2 What is an agonist? Drug, hormone, toxin, autacoid or neurotransmitter that elicits a biological effect when it interacts with receptors \u2013 bethanechol (used for urinary retention) combines with muscarinic ACh […]<\/p>\n","protected":false},"author":4934,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"page-template\/generic-template.php","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-45614","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"\nAgonists, Antagonists and Drug Toxicity - UTS Pharmacology<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Agonists, Antagonists and Drug Toxicity - UTS Pharmacology\" \/>\n<meta property=\"og:description\" content=\"Contents References Rang HP, Dale MM, Ritter JM, Flower RJ, Henderson, G (2016) Pharmacology, 8th Edition, Churchill Livingstone, Sydney. How drugs act: general principles\u2013 Section 1, part 2 What is an agonist? Drug, hormone, toxin, autacoid or neurotransmitter that elicits a biological effect when it interacts with receptors \u2013 bethanechol (used for urinary retention) combines with muscarinic ACh […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/\" \/>\n<meta property=\"og:site_name\" content=\"UTS Pharmacology\" \/>\n<meta property=\"article:modified_time\" content=\"2019-09-16T08:58:25+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-content\/uploads\/sites\/8\/2019\/09\/bethanechol-00.png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"6 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/\",\"url\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/\",\"name\":\"Agonists, Antagonists and Drug Toxicity - UTS Pharmacology\",\"isPartOf\":{\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-content\/uploads\/sites\/8\/2019\/09\/bethanechol-00.png\",\"datePublished\":\"2019-08-02T20:17:27+00:00\",\"dateModified\":\"2019-09-16T08:58:25+00:00\",\"breadcrumb\":{\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#primaryimage\",\"url\":\"https:\/\/wordpress-futures-prod.s3.ap-southeast-2.amazonaws.com\/wp-content\/uploads\/sites\/8\/2019\/09\/03125836\/bethanechol-00.png\",\"contentUrl\":\"https:\/\/wordpress-futures-prod.s3.ap-southeast-2.amazonaws.com\/wp-content\/uploads\/sites\/8\/2019\/09\/03125836\/bethanechol-00.png\",\"width\":2022,\"height\":311},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Agonists, Antagonists and Drug Toxicity\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/#website\",\"url\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/\",\"name\":\"UTS Pharmacology\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/educationexpress.uts.edu.au\/pharmacology\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Agonists, Antagonists and Drug Toxicity - UTS Pharmacology","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/","og_locale":"en_US","og_type":"article","og_title":"Agonists, Antagonists and Drug Toxicity - UTS Pharmacology","og_description":"Contents References Rang HP, Dale MM, Ritter JM, Flower RJ, Henderson, G (2016) Pharmacology, 8th Edition, Churchill Livingstone, Sydney. How drugs act: general principles\u2013 Section 1, part 2 What is an agonist? Drug, hormone, toxin, autacoid or neurotransmitter that elicits a biological effect when it interacts with receptors \u2013 bethanechol (used for urinary retention) combines with muscarinic ACh […]","og_url":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/","og_site_name":"UTS Pharmacology","article_modified_time":"2019-09-16T08:58:25+00:00","og_image":[{"url":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-content\/uploads\/sites\/8\/2019\/09\/bethanechol-00.png","type":"","width":"","height":""}],"twitter_card":"summary_large_image","twitter_misc":{"Est. reading time":"6 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/","url":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/","name":"Agonists, Antagonists and Drug Toxicity - UTS Pharmacology","isPartOf":{"@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/#website"},"primaryImageOfPage":{"@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#primaryimage"},"image":{"@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#primaryimage"},"thumbnailUrl":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-content\/uploads\/sites\/8\/2019\/09\/bethanechol-00.png","datePublished":"2019-08-02T20:17:27+00:00","dateModified":"2019-09-16T08:58:25+00:00","breadcrumb":{"@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#primaryimage","url":"https:\/\/wordpress-futures-prod.s3.ap-southeast-2.amazonaws.com\/wp-content\/uploads\/sites\/8\/2019\/09\/03125836\/bethanechol-00.png","contentUrl":"https:\/\/wordpress-futures-prod.s3.ap-southeast-2.amazonaws.com\/wp-content\/uploads\/sites\/8\/2019\/09\/03125836\/bethanechol-00.png","width":2022,"height":311},{"@type":"BreadcrumbList","@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/agonists-antagonists-and-drug-toxicity\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/"},{"@type":"ListItem","position":2,"name":"Agonists, Antagonists and Drug Toxicity"}]},{"@type":"WebSite","@id":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/#website","url":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/","name":"UTS Pharmacology","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"}]}},"_links":{"self":[{"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/pages\/45614","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/users\/4934"}],"replies":[{"embeddable":true,"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/comments?post=45614"}],"version-history":[{"count":59,"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/pages\/45614\/revisions"}],"predecessor-version":[{"id":46652,"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/pages\/45614\/revisions\/46652"}],"wp:attachment":[{"href":"https:\/\/educationexpress.uts.edu.au\/pharmacology\/wp-json\/wp\/v2\/media?parent=45614"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}