Inflammation
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What is an antacoid?
Mediators of inflammation produced locally around the site of stimulus to inflammation
What are the conceptual challenges in developing new anti-inflammatory drugs?
Cost Lack of oral availability
How do histamine a fulfil Dale’s criteria for a pharmacological mediator?
Present in histaminergic neurones Store in granules Upon antigen-IgE cross-linking, granules are released Effects shown at H receptors Terminated by histaminase
How does histamine contribute to a local inflammatory response?
Causes vasodilation of the small arteriolar and precapillary sphincters Causes the release of CGRP and other vasodilatory by anti-dromic impulses in sensory nerve fibres
How does histamine contribute to anaphylaxis?
Causes smooth muscle contraction in bronchi
Name 3 chemical mediators which regulate acid secretion from parietal cells
Histamine (+) Gastric (+) Prostaglandins E(2) and I(2) (-)
Describe ranitidine.
H(2) antagonist Heals duodenal ulcers
Describe terfenidine.
H1 non sedative antagonist No entry to CNS
Describe diphenhydramine.
H1 antagonist Used to treat motion sickness Can cross BBB
What is an eicosanoid?
Locally produced lipids Work in the 10(-12)M range Small t(1/2) Metabolised into active prostaglandin
Describe the biosynthesis of PGE(2)
Phospholipid is converted into arichidonic acid by phospholipase A(2) arichidonic acid is converted to PGG(2) by cyclooxygenase PGG(2) converted to PGH(2) by cycloendoperoxides PGH(2) converted to PGE(2) by PG isomerise reductase
How is the biosynthesis of PGE(2) targeted by anti-inflammatory drugs?
Lipocortin inhibits phospholipase A(2) NSAIDS inhibit cyclooxygenase
What are the main side-effects of NSAIDs?
Gastro-intestinal bleeding
What is the biological mechanism behind NSAID gastrointestinal bleeding?
NSAIDs block cox-1, inhibiting PGE(2) production Reducing PGE(2) increases acid production Acid irritates gastrin mucosa increasing susceptibility to ulceration They prolong bleeding by reducing the platelet stickiness
How do cox-2 inhibitors avoid gastrointestinal bleeding?
Cox-2 doesn’t affect platelet stickiness
Why is aspirin used for platelet inhibition and not other NSAIDs?
Aspirin is the only NSAID which irreversibly inhibits cyclooxygenase. This means much lower doses can be used and less frequently
Uses of prostaglandin analogues.
Abortion Labour induction Postcoital contraception Peptic ulcer treatment
Main causative agents of peptic ulcer formation.
H. pylori NSAIDs Stress Diet
What is the HPA axis?
Hypothalamic- pituitary- adrenal axis A complex set of direct feedback interactions among the 3 endocrine glands Regulates glucocorticoids i.e cortisol
How does the HPA axis contribute to the regulation of inflammation?
Glucocorticoids are anti-inflammatory They suppress the production of antacoids Inhibitor of induction and effector phases of immune response
Omeprazole
Proton pump inhibitor Treats peptic ulcers Inhibits H/K ATPase of parietal cell Decreases gastric acid secretion
Aluminium hydroxide.
Antacid Neutralises gastric acid
Sucralfate.
Coating agent Provides protection to GI epithelium
Misoprostol.
Prostaglandin Inhibits acid production