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respiratory system drugs

respiratory system drugs


    Drugs affecting the respiratory system





    I- Overview

    Drugs can be deliverd to the lung by
    inhalation : preferred as
    The drug is deliverd directly to the target tissues
    Effective in doses do not cause significant systemic side effects
    oral route
    parenteral route



    Main mechanisms of action
    Relaxing bronchial smooth muscles
    Modulating the inflammatory response



    II- Drugs used to treat asthma


    Asthma is a chronic disease characterised by episodes of acute bronchoconstriction causing
    Shortness of breath
    Cough
    Chest tightness
    Wheezing
    Rapid respirations

    The goal of the therapy is to
    Relieve symptoms
    Prevent recurrence of asthmatic attacks if possible


    Role of inflammation in asthma

    Airflow obstruction in asthma is due to bronchconstriction resulting from
    contraction of bronchial smooth muscle
    inflammation of the bronchial wall
    increased mucous secretions



    Asthmatic attacks may be related to
    Recent exposure to allergans
    Inhaled irritants
    leading to bronchial hyperactivity and inflammation of the airway mucosa


    The symptoms of asthma may be effectively treated by several drugs but none of them provide a cure for this obsructive lung disease




    A-Adrenergic agonists



    Inhaled B2 agonists(as direct bronchodilators) ..are drug of choice for mild asthma (occurs occasionaly with intermittent symptoms)
    Have no anti-inflammatory effects
    Should not be used as the sole therapeutic agents for patient with chronic asthma



    Short acting : used as a rescue agents to combat acute
    bronchoconstriction

    ex :terbutaline - albuterol - pirbuterol
    Onset : rapid (15-30)minutes
    Duration : (4-6)hours



    Long acting drugs

    ex:salmetrol
    Onset :slow so should not be used in acute asthmatic attack
    Duration : at least 12 hours



    Prescriped only for administration at regular intervals and not to relieve symptoms



    B- Corticosteroids


    ex : beclomethazone - triamcinolone


    Drug of first choice in patients with moderate to severe asthma who require inhalation of B2 agonists more than once daily
    To be effective in controlling inflammation ,glucocorticoid must be taken continuously




    Actions on the lung

    Inhaled glucocorticoids decrease the number and activity of cells involved in airway inflammation
    Prolonged(several months)inhalation of steroids reduces the hyperresponsiveness of the airway smooth muscle to a variety of bronchoconstriction stimuli such as
    allergans - irritants - cold air - exercise


    The most common adverse effect associated with the use of inhaled glucocorticoids is oropharyngeal candidiasis = oral thrush




    C- Cromolyn & nedcromil - inhalations


    Effective prophylactic anti-inflammatory agents
    Not useful in management of acute ashmatic attack because they are not direct bronchodilators
    Pretreatment with cromolyn blocks bronchoconsriction induced from allergans and exercise
    Useful in reducing symptoms of allergic rhinitis




    D- Cholinergic antagonists


    ex: ipratropium

    Has slow onset and nearly free of side effects
    Less effective than B agonists but useful in patients unable to tolerate them



    E- Theophylline

    Relieves airflow obstruction in chronic asthma
    Previously,it was the main stay of asthma therapy but now it is largely replaced with B agonists and corticoids
    Has a narrow therapeutic window so overdose of it may cause seizures or potentially fatal arrythmias





    III- Drugs used to treat allergic rhinitis



    Rhinitis : an inflammation of the mucous membranes of the nose and is characterized by
    Sneezing -nasal itching - watery rhinorrhea - congestion




    A- Antihistamines = H1 receptor blockers


    ex : diphenhydramine - chlorpheniramine - loratadine - terfenadine - astemizole


    Useful in treating the symptoms of allergic rhinitis
    When congestion is a feature of rhinitis , combination with decongestants is effective





    B- Alpha adrenergic agonists = nasal decongestants


    ex: phenylephrine - oxymetazoline

    Constrict dilated arterioles in nasal mucosa and reduce airway resistance
    Should not be used no longer than several days because rebound nasal congestion often occurs upon discontinuence of these drugs




    C- corticosteroids


    Topical steroids may be more effective than antihistamines in relieving the nasal symptoms of both allergic and non allergic rhinitis
    Treatment of chronic rhinitis may not result in improvement until 1 to 2 weeks after starting therapy



    D- Cromolyn

    Intanasal cromolyn may be useful particularly when administerd before contact with an allergan





    IV- Drugs used to treat chronic obstructive pulmonary disease COPD



    It is a chronic irreversible obstruction of airflow
    Smoking is the greatest risk factor for COPD
    This disease may respond to
    Anticholinergic agents


    B adrenergic agents e.g : impratropium

    Theophylline

    These three classes does not cure the disease or even significantly slow its progress
    Glucocorticoids : may be helpful in the treatment of acute exacerbations in some patients





    V- Drugs used to treat cough



    ex : codeine -hydrocodone -hydromorphone

    at doses lower than required for analgesia they can
    decrease the sensitivity of the CNS cough centers to peripheral stimuli
    decrease mucosal secretion


    Dextromethorphane : synthetic derivative of morphine


    Supress the response of the cough center
    Has no analgesic or addictive potential
    Less constipating than codeine


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