DRUGS ACTING ON THE RESPIRATORY ORGANS 43 



Strychnine and atropine are respiratory stimulants ; atropine is indi- 

 cated where exudation is abundant, while ammonium carbonate is pre- 

 scribed to increase secretion. Certain drugs sometimes cause in latge 

 doses Cheyne-Stokes breathing in animals, e.g., opium, chloral, bromides, 

 digitalis, ammonium carbonate and strychnine, owing to disturbance of 

 the respiratory centre. Drugs depressing the respiratory centre are not 

 used for this purpose but because they also relieve cough. 



Drugs Relaxing Spasm of the Bronchial Muscular Tunic and 

 Relieving Cough. 



LOCALLY. 



White of egg Linseed tea 



Mucilage Syrups 



External counter-irritation and heat. 



SYSTEMICALLY. 



Opium Nitrites 



Codeine Chloral 



Heroin Bromides 



Hyoscyamus Chloroform 



Stramonium Phenacetin 



Cannabis Indica Adrenalin 



Uses of Drugs Allaying Spasm and Cough., 



Coughing is a reflex act following irritation of sensory nerve endings 

 in any part of the respiratory tract (usually of afferent vagal branches), 

 in the pharynx, pleura, ears, teeth, stomach and liver. Sensory impulses 

 conveyed to the reflex centre for coughing, — near the respiratory centre 

 in the medulla, — are there transformed into motor impulses and result in 

 coughing. Drugs may stop coughing by acting locally to relievfe conges- 

 tion and irritation (demulcents) or they may exert a topical sedative 

 action on the nerve endings. They also act systemically by quieting the 

 reflex centre for coughing, or the sensory or motor ner-ve endings; also 

 by abating congestion in promoting secretion (expectorants), or in influ- 

 encing the circulation. 



Cough may be beneficial when it assists the expulsion of exudation, 

 but is not so when it is constant and ineffective, as in congestion of the 

 trachea, bronchial mucous membranes, lungs or pleura; in pulmonary 

 consolidation; and in coughs originating outside of the respiratory tract. 

 We should try to arrest coughing by agents removing the cause (conges- 

 tion or irritation), such as counter-irritants, expectorants, local applica- 

 tions (sprays, inhalations) and heart stimulants, but if these are inefiicient 

 and coughing is immoderate, we may resort to the use of sedative agents. 

 Some preparation of opium is most frequently employed to stop coughing, 

 but should be avoided if cyanosis exists, since inspiratory and expulsive 

 efforts are weakened by the drug. Belladonna, on the other hand, stimu- 

 lates the respiratory centres and arrests cough by depressing both the 

 afferent and efferent vagal terminations in the lungs, while — like opium — 

 lessening secretion. These drugs are often combined. When spasm of 

 the bronchioles exists, as in asthma, adrenalin is particularly valuable. 



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