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PHARMACOLOGY OF RESPIRATORY DRUGS

PHARMACOLOGY OF RESPIRATORY DRUGS. Susanne Young May 04’. content. Physiology/ sites of action Review drugs in use Main considerations in anaesthesia. Control of bronchial tone+++. ß2. Muscarinic ACh. Ad Cyclase. G.Cyclase. +. _. GTP. ATP. cAMP. Kinases. cGMP. PDE. 5’AMP.

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PHARMACOLOGY OF RESPIRATORY DRUGS

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  1. PHARMACOLOGY OF RESPIRATORY DRUGS Susanne Young May 04’

  2. content • Physiology/ sites of action • Review drugs in use • Main considerations in anaesthesia

  3. Control of bronchial tone+++ ß2 Muscarinic ACh Ad Cyclase G.Cyclase + _ GTP ATP cAMP Kinases cGMP PDE 5’AMP

  4. Prostaglandin Synthesis Phospholipids PLA2 Arachidonic Acid Lipoxygenase COX PGG2 5HPETE Leukotrienes IgE TXA2 PGI2

  5. Common Respiratory Drugs • ß2 agonists • Long acting ß2 agonists • Anti-cholinergics • Inhaled steroids

  6. Less common • Leukotriene receptor antagonist • Methylxanthines • Sodium cromoglycate

  7. ß2 AGONISTS • Salbutuamol, Bricanyl, Terbutaline • Less selective in hi dose- get ß1effect • 100mcg per puff lasts 4hrs or so. • Salmeterol, Eformoterol • Last 12 hrs or so • 15x more potent at ß2 than Salbutamol

  8. Side Effects • ß2 Muscle tremor • Hypokalaemia (Na+/K+ ATPase) • ß1 Anxiety • Nausea and vomitting • Hypertension • Tachyarryhthmias • Dizziness/ Headache

  9. Anticholinergics • 200 yrs ago Datura plants were smoked! • Atropine later • Then more selective agents • Ipatropium • Peak effect 30-60 mins • Lasts 6hrs or so • Spireva= Tiotropium- longer acting o.d egg

  10. Inhaled steroids • Becotide/ Flixotide/ Pulmicort • Dose range 100 mcg to 1g per day • Peak effect 6-12hrs • Anti- inflammatory • Sensitise ß2 receptors • Prevent tachyphlaxis

  11. Methylxanthines • Caffeine related! • In use since 1930 • Very alkaline- never give im • Therapeutic range 10-20mg/l • Half life increased in: CCF, elderly • Decreased in smokers, enzyme induction • Side Effects incl: • Inc HR, FOC, arrythmias. • Inc GORD. Hypokalaemia, seizures

  12. Methylxanthines (cont) • Proposed mechanisms: • PDE Inhibition • Adenosine (causes mast cell degranulation) Receptor Antagonism • Prostaglandin Inhibition • Endogenous CA release

  13. Leukotriene Receptor Antagonists • Good in rhinitis • Not better than but additive to steroids • Steroid sparing • Preventer

  14. Sodium Cromoglycate • Mast cell stabiliser, closes Ca++ channels • May be of use in allergic asthma in kids • Preventer, but • Not as effective as inhaled steroid

  15. Considerations/ Conclusions • ? Avoid Histamine releasing drugs • ? Avoid NSAID’s • ß2 agonists, corticosteroids, Theophylline (and Sux) all cause Hypokalaemia • Arrythmias are potentiated by hypoxia

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