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PHARMACOLOGY OF RESPIRATORY DRUGS

PHARMACOLOGY OF RESPIRATORY DRUGS

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PHARMACOLOGY OF RESPIRATORY DRUGS

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  1. PHARMACOLOGY OF RESPIRATORY DRUGS by Ma. Elizabeth V. Rey-Matias, M.D., PTRP, PTR, MHPEd, PhD SPED

  2. RESPIRATORY DRUGS Acute, minor problems--nasal congestion, coughing, and seasonal allergies Chronic, serious airway obstructions, such as bronchial asthma, chronic bronchitis, and emphysema

  3. Antitussives suppress coughing related to common cold and other minor throat irritations  often combined with aspirin or acetaminophen to treat cold as well as with other respiratory tract agents

  4. Antitussives – for short-term use in relieving symptomatic coughing. extensive use not advised coughing -defense mechanism that expel mucus and foreign material from the URT.

  5. antitussives -reduce the ability of coughing to raise secretions helpful in treating annoying dry cough but extensive use not justified codeine and similar opiate derivatives suppress the cough reflex by a central inhibitory effect

  6. Other nonopioid antitussives inhibit the irritant effects of histamine on the respiratory mucosa or by a local anesthetic action on the respiratory epithelium. adverse effect of most antitussives is sedation. Dizziness and GI upset may also occur.

  7. Decongestants treat nasal congestion and mucous discharge from the upper respiratory tract- usually alpha-1–adrenergic agonists

  8. bind to alpha-1 receptors located on the blood vessels of the nasal mucosa and stimulate vasoconstriction, drying up the mucosa and decreasing nasal congestion

  9. Alpha-1 agonists used as decongestants Mimic effects of increased sympathetic nervous system activity, and can cause serious cardiovascular and central nervous system (CNS) excitation.

  10. abuse should be avoided adverse effects- headache, dizziness, nervousness, nausea, and cardiovascular irregularities (increased blood pressure, palpitations).

  11. Antihistamines Antihistamines used for sedation or to treat parkinsonism. treat the respiratory allergies

  12. Histamine-endogenous chemical involved in the normal regulation of certain physiologic functions (gastric secretion, CNS neural modulation), hypersensitivity (allergies)

  13. Histamine exerts its effects on four receptor: the H1,H2, H3, and H4 receptors. Antihistamines-are drugs that specifically block the H1 subtype of histamine receptors; that is, the effects of histamine during allergic reactions, respiratory infections,

  14. H2 receptors -regulation of gastric acid secretion. H2 antagonists may help control gastric secretion in peptic ulcer H3 receptor, involved in the local regulation of histamine release from CNS nerve terminals.

  15. Significance of H3 and H4 receptors remains to be determined. antihistamine effects on the upper respiratory tissues -decrease nasal congestion, mucosal irritation and discharge (rhinitis, sinusitis), and conjunctivitis that are caused by inhaled allergens.

  16. Antihistamines decrease the coughing and sneezing associated with cold. do not reverse bronchospasm associated with asthma, used as an adjunct in patients with asthma to help control rhinitis and sinusitis

  17. adverse effects associated with antihistamines are sedation, fatigue, dizziness, blurred vision, and incoordination. “first-generation” antihistamines cross the blood-brain barrier causing CNS-related side effects such as sedation and psychomotor slowing. Newer “second-generation”antihistamines, do not easily cross the bloodbrain barrier, and the risk of sedation and other CNS side effects is reduced

  18. nonsedating antihistamines, include cetirizine (Zyrtec), loratadine (Claritin), desloratidine (Clarinex), and fexofenadine (Allegra) nonsedating antihistamines such as astemizole and terfenadine may be cardiotoxic, and may cause severe ventricular arrhythmias

  19. Mucolytics and Expectorants Mucolytic -decrease the viscosity of respiratory secretions. Expectorant –facilitate production and ejection of mucus. Prevent accumulation of thick, viscous secretions that can clog respiratory passages and lead to pulmonary problems. Expectorants and mucolytics are used in acute disorders ranging from the common cold to pneumonia, as well as in chronic disorders such as emphysema and chronic bronchitis. often used in combination with other agents (e.g., antitussives, decongestants, bronchodilators). The primary mucolytic drug currently in use is acetylcysteine (Mucomyst, Mucosil). MUCOLYTIC drug Work by splitting the disulfide bonds of respiratory mucoproteins, thus forming a less viscous secretion. This drug has antioxidant effects, and some of acetylcysteine’s benefits may be due to its ability to decrease free-radical damage in the respiratory tissues. Acetylcysteine is usually administered directly to the respiratory mucosa by inhalation or intratracheal instillation (through a tracheostomy). Primary adverse effects with this drug include nausea, vomiting, inflammation of the oral mucosa (stomatitis), and rhinorrhea. Several expectorant agents have been used in the past, but guaifenesin is the only drug currently acknowledged by the FDA to have evidence of therapeutic effects. increase the production of respiratory secretions, thus encouraging ejection of phlegm and sputum. Guaifenesin usually administered orally in some form of syrup or elixir, is often combined with other agents in over-the-counter preparations, which are known by many different trade names. primary adverse effect associated with Guaifenesin is gastrointestinal upset,

  20. Expectorants and mucolytics used to treat common cold, pneumonia, and chronic disorders such as emphysema and chronic bronchitis. often used in combination with other agents (e.g., antitussives, decongestants, bronchodilators).

  21. The primary mucolytic drug currently in use is acetylcysteine (Mucomyst, Mucosil). splitting the disulfide bonds of respiratory mucoproteins, thus forming a less viscous secretion.

  22. has antioxidant effects, and some of acetylcysteine’s benefits may be due to its ability to decrease free-radical damage in the respiratory tissues. Acetylcysteine is usually administered directly to the respiratory mucosa by inhalation or intratracheal instillation (through a tracheostomy). Primary adverse effects with this drug include nausea, vomiting, inflammation of the oral mucosa (stomatitis), and rhinorrhea. Several expectorant agents have been used in the past, but guaifenesin is the only drug currently acknowledged by the FDA to have evidence of therapeutic effects. increase the production of respiratory secretions, thus encouraging ejection of phlegm and sputum. Guaifenesin usually administered orally in some form of syrup or elixir, is often combined with other agents in over-the-counter preparations, which are known by many different trade names. primary adverse effect associated with Guaifenesin is gastrointestinal upset,

  23. adverse effects -nausea, vomiting, inflammation of the oral mucosa (stomatitis), and rhinorrhea. guaifenesin -only drug acknowledged as expectorant by the FDA to have evidence of therapeutic effects.

  24. increase the production of respiratory secretions, thus encouraging ejection of phlegm and sputum. Guaifenesin usually administered orally in some form of syrup or elixir, often combined with other agents in over-the-counter preparations

  25. primary adverse effect associated with Guaifenesin is gastrointestinal upset

  26. Drugs Used to Maintain Airway Patency in COPD primary goal –prevent/ reverse bronchial constriction and obstruction of airways by • bronchodilators(beta-adrenergic agonists, xanthine derivatives, anticholinergics) • anti-inflammatory agents (glucocorticoids, others). Beta-Adrenergic Agonists Rationale for Use and Mechanism of Action Respiratory smooth-muscle cells contain the beta-2 subtype of adrenergic receptors. Stimulation of these beta-2 receptors results in relaxation of bronchiole smooth muscle. drugs that stimulate these beta-2 adrenergic receptors (i.e., betaadrenergic agonists) produce bronchodilation and can be used to prevent or inhibit airway obstruction in bronchospastic diseases. Beta-adrenergic agonists are believed to induce smooth-muscle relaxation by, stimulation of the beta-2 receptor increases activity of the adenyl cyclase enzyme. This enzyme increases the production of intracellular cyclic adenosine monophosphate (cAMP). The cAMP acts as an intracellular second messenger, which then increases the activity of other enzymes such as protein kinase. The increased protein kinase activity ultimately inhibits smooth-muscle contraction, probably by adding a phosphate group to specific contractile proteins. Specific Agents and Method of Administration Beta-adrenergic agonists used to induce bronchodilation some drugs are nonselective and stimulate alpha and beta receptors fairly equally. Other agonists are more selective and preferentially stimulate the beta-adrenergic receptors. Finally, the beta-2–specific agents are the most selective and tend to bind preferentially to beta-2 receptors. Beta-2–selective agonists when administered systemically - less chance of side effects caused by stimulation ofNother adrenergic receptors located on other tissues (e.g., beta-1 receptors on the myocardium). When administered via inhalation, however, the issue of adrenergic receptor selectivity becomes less important because the drug is applied directly to the respiratory drugs (formoterol, salmeterol) - long-acting beta-adrenergic agonists. may provide more stable and sustained bronchodilation in conditions such as asthma. Beta-adrenergic drugs can be administered orally, subcutaneously, or by inhalation. Inhalation of these drugs is often the preferred method of administration in treating respiratory disorders. Inhalation allows the drug to be delivered directly to the respiratory tissues with a minimum of systemic side effects because of its absorption into the systemic circulation. 4 The onset of action is also more rapid with inhalation. Oral or subcutaneous administration is usually associated with more side effects. However, when administered orally or subcutaneously, beta agonists may reach the more distal branches of the airway to a greater extent. The bronchioles are usually constricted during an asthmatic attack, and the drug may not reach the distal respiratory passages when administered by inhalation. Several beta agonists are available in metereddose inhalers (MDIs) for inhalation administration. Another method of inhaling beta agonists is through a nebulizer

  27. Beta-Adrenergic Agonists Stimulation of beta-2 receptors results in relaxation of bronchiole smooth muscle. betaadrenergic agonists produce bronchodilation and can be used to prevent or inhibit airway obstruction in bronchospastic diseases.

  28. Beta-adrenergic agonists Stimulation of beta-2 receptor increases activity of the adenylcyclase enzyme. This enzyme increases the production of intracellular cyclic adenosine monophosphate (cAMP).

  29. The cAMP acts as an intracellular second messenger, which increases the activity of protein kinase. increased protein kinase activity ultimately inhibits smooth-muscle contraction

  30. some drugs are nonselective and stimulate alpha and beta receptors fairly equally. the beta-2–specific agents are the most selective and tend to bind preferentially to beta-2 receptors.

  31. Beta-2–selective agonists when administered systemically - less chance of side effects Do not stimulate other adrenergic receptors located on other tissues (e.g., beta-1 receptors on the myocardium).

  32. drugs (formoterol, salmeterol) - long-acting beta-adrenergic agonists provide more stable and sustained bronchodilation Beta-adrenergic drugs can be administered orally, subcutaneously, or by inhalation.

  33. Inhalation-often the preferred method of administration in treating respiratory disorders. -allows the drug to be delivered directly to the respiratory tissues with less side effects -onset of action is also more rapid with inhalation.

  34. Oral or subcutaneous administration is associated with more side effects.

  35. when administered orally or subcutaneously, beta agonists may reach the more distal branches of the airway to a greater extent. The bronchioles are usually constricted during an asthmatic attack, and the drug may not reach the distal respiratory passages when administered by inhalation.

  36. Several beta agonists are available in metereddose inhalers (MDIs) for inhalation administration. Another method of inhaling beta agonists is through a nebulizer.

  37. Nebulizers- useful alternative for those who cannot master MDI delivery. beta-2 drugs can be delivered via a dry powder inhaler (DPI). DPIs may be easier for certain patients who lack the coordination and timing needed to use an MDI.

  38. Side Effects excessive use of beta-2 drugs promote airway irritation, thus increasing the incidence and severity of bronchospastic attacks. Prolonged use of beta-2 drugs cause tolerance; the dose must be increased to achieve therapeutic effects when this occurs.

  39. Adrenergic agonists stimulate beta-1 receptors may cause cardiac irregularities if given through the systemic circulation. stimulation of CNS adrenergic receptors -nervousness, restlessness, and tremor.

  40. Adverse effects are less when beta-adrenergic agonists are used locally via inhalation.

  41. Xanthine derivatives theophylline, caffeine, theobromine Theophylline produce bronchodilation in asthma and other forms of reversible airway obstruction (bronchitis, emphysema)

  42. Theophylline and caffeine -potent CNS stimulants side effects -related to CNS excitation enhance bronchodilation by inhibiting the phosphodiesterase (PDE) enzyme In bronchial smooth-muscle cells.

  43. PDE breaks down cAMP; inhibiting this enzyme results in higher intracellular cAMP concentrations. cAMP -second messenger that brings about respiratorysmooth-muscle relaxation and subsequent bronchodilation.

  44. By inhibiting PDE, theophylline prolongs effects of second messenger and increase bronchodilation. PDE inhibition decrease function of inflammatory cells and inhibit production of inflammatory mediators --theophylline has anti-inflammatory properties

  45. theophylline’s benefits are the anti-inflammatory properties rather than to a direct bronchodilating effect. Theophylline -act as an adenosine antagonist. Adenosine bind to receptors on the smooth-muscle cells and cause contraction.