DRUGS ACTING ON THE RESPIRATORY SYSTEM 

CHAPTER FIVE

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Learning Objectives
At the end of the chapter the students will be able to learn:

• Detail description of drug used to treat bronchial asthma, cough, nasal congestion as a result of some disorders and allergic condition.
• Broad classification of drugs used to treat bronchial asthma
• The pharmacokinetics, mechanism of action, side effects of each group of drugs used to treat bronchial asthma.

INTRODUCTION
The respiratory system includes the upper airway passages, the nasal cavities, pharynx and trachea as well as the bronchi and bronchioles. Respiration is the exchange of gases between the tissue of the body and to outside environment. It involves breathing in of an air through the respiratory tract, uptake of oxygen from the lungs, transport of oxygen through the body in the blood stream, utilization of oxygen in the metabolic activities (cells and removal of carbon dioxide from the body.

Drug therapy of pulmonary disorders is generally directed towards altering a specific physiologic function. The chapter will focus on drugs used to treat some of the more common disorders affecting the respiratory system particularly bronchial asthma, allergies and congestions associated with certain respiratory disorders.

Bronchial Asthma
Asthma is physiologically characterized by increased responsiveness of the trachea and bronchi to various stimuli and by wide spread narrowing of the airways that changes in severity either spontaneously or as a result of therapy.

Impairment of airflow in bronchial asthma is caused by three bronchial abnormalities.

• Contraction of airway smooth muscles
• Thickening of bronchial mucosa from edema and cellular infiltration
• Inspissations in the airway lumen of abnormally thick, viscid plugs of excessive mucus.

Exercise

1. What are the drugs used to treat bronchial asthma and how are they classified?
2. Explain mechanism of action and pharmacokinetic properties of methylxanthines.
3. What are the side effects and contraindications of glucocorticoids?
4. What are differences between antitussives and expectorants? Give example.
5. Give examples of decongestant drugs and their side effects.