Autacoids and antagonists

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Autacoids and antagonists

  1. 1. Drugs acting to stop pain andinflammation
  2. 2. Drugs acting to stop pain andinflammation Pain, inflammation and fever is mainly triggered by Autacoids The major autacoids involved in pain, fever and inflammation are histamines and prostaglandins
  3. 3. Autacoids The word autacoids comes from the Greek "Autos" (self) and "Acos" (relief, i.e. drug). Autacoids are biological factors which act like local hormones, have a brief duration, act near the site of synthesis, and are not blood borne
  4. 4. Introduction Agents that may induce release of autacoids include - Chemical irritants - UV light - Trauma - bacterial toxins - immune irritants
  5. 5. Major classes of autacoids Class Example Histamine Biogenic Amines Serotonin (5 HT) Prostaglandins (Eicosanoids) , leukotrienes, Phospholipids Thromboxanes, Platelet activating factors Derived (PAF) Angiotensin and Kinins (Bradykinin and Polypeptides Kallikidin)
  6. 6. Stopping pain, fever andinflammation There are two main groups of pain killers -Autacoids antagonists -CNS acting nerve blockers (alpha 2 adrenergic drugs) AntihistaminesAutacoids antagonists Prostaglandin Synthesis inhibitors
  7. 7. Antihistamines (Antagonists) Antihistamines act by blocking histamine receptors There are four Histamine receptors designated as H1 H2, H3, and H4, each with different function Only H1 is involved with pain All Histamines antagonists are competitive blockers of histamine receptors
  8. 8. Histamine Receptors blockersType Examples Main functionsH1 receptor Diphenhydramine To treat Mepyramine maleateblockers Promethazine allergic hydrochloride reactions Pheniramine maleate AntazolineH2 receptor Cimetidine To reduce Burimamideblockers Metiamide Gastric acid Ranitidine releaseH3 receptor Burimamide To treat Impromidine neurodegenerativeblockers Theoperamide conditionsH4 blockers Thioperamide UI
  9. 9. Non-Steroidal AntiinflammatoryDrugs (NSAIDs) These are basically prostaglandin (PG) synthesis inhibitors Remember that prostaglandin is an autacoid that will engineer pain stimuli
  10. 10. How is prodtaglandin synthesized
  11. 11. How is prodtaglandin synthesized
  12. 12. Common PG synthesis inhibitors Aspirin Acetaminophen Phenylbutazone Dipyrone
  13. 13. Morden NSAIDs Naproxen Flunixin meglumine (banamine) Meclofenamic acid Ibuprofein and indomethacin Orgotein Dimethyl sulphoxide (DMSO) Polysulfated glycosaminoglycans (Adequan)
  14. 14. Mechanisms of Action of NSAIDs Binding (reversibly and irreversibly) to cyclo-oxygenase (PG synthase) - Aspirin – Irreversibly - Acetaminophen – reversibly - Phenylbutazone – Irreversibly - Dipyron- Irreversibly - Naproxein – Irreversibly - Flunixin – Irreversibly - Meclofenamic acid - Irreversibly
  15. 15. Mechanisms of Action of NSAIDs Other mechanisms Orgotein – Breaks down superoxide free radicals to peroxides DMSO – It also trap free radicals like superoxides Adequan – Inhibits the loss of cartilaginous mucopolysaccharides
  16. 16. Alpha2-Adrenergic Agonists Xylazine Detomidine

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