Pulmonary system bronchial asthma

Sympathomimetics (drugs that mimic the sympathetic nervous system) are used primarily to treat reversible airway obstruction caused by bronchospasm associated with acute and chronic bronchial asthma, exercise-induced bronchospasm, bronchitis, emphysema, bronchiectasis (abnormal condition of the bronchial tree), or other obstructive pulmonary diseases. 

The drngs generally are administered as eye drops and have an onset in approximately 30 minutes with a duration of 12 to 24 honrs. While topically administered P-blockers usnally are well tolerated, systemic absorption can lead to adverse cardiovascular and pulmonary effects in susceptible patients. They, therefore, should be used with great caution in glaucoma patients at risk for adverse systemic effects of p-receptor antagonists (e.g., patients with bronchial asthma, or those with bradyarrhythmias). 

The primary route of exposure to H2S is inhalation. Hydrogen sulfide is classified as a chemical asphyxiant. A single breath of HjS at a concentration of 1000 ppm is sufficient to kill an individual. Prolonged exposure at 250 ppm levels can cause pulmonary edema (the lungs filling with fluid), which can lead to death. However, even at low concentrations (less than 10 ppm), H2S may cause irritation of the eye and respiratoiy system (including the nose, mouth, and bronchial tubes). The effect of hydrogen sulfide can be exacerbated if the individual already suffers from such a pulmonaiy disease as asthma. 

Bronchodilation is another property of belladonna alkaloids of potential usefulness. Due to relaxation of the smooth musculature of bronchial passageways, this effect has found applications in asthma and other pulmonary obstructive conditions. At one time the smoking of cigarettes made of stramonium leaves was popular. More recently, atropine, quater-nized with isopropyl bromide (Ipratropium, Fig. 8-13) has been introduced as an aerosol for inhalation. This renewed interest in antimuscarinics resulted in part from clarifications of the role of the parasympathetic system in bronchial obstructions. The availability of a potent agent such as atropine in a poorly absorbed form (i.e., quatemized) would minimize systemic effects following inhalation. Ipratropium bromide does not cross the BBB. It is longer acting and more bronchoselective than atropine methylbromide and exhibits no CNS effects. 

---