Bronchial Asthma- Stimulants

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1. Allergens

Allergic asthma is dependent on IgE response controlled by T and B

lymphocytes and activated by the interaction of antigen with mast cells-bound

IgE molecule. Most of the allergens are airborne and to induce a state of

sensitivity, they must be reasonably abundant for considerable period of time.

Allergic asthma is frequently seasonal and it is most after observed in

children and young adults. A non-seasonal form may result from allergy to

feathers, animal dander, dust mites, molds and other antigens that are present

continuously in the environment.

2. Pharmacological stimuli

The drugs most commonly associated with the induction of acute

episodes of asthma are aspirin, colouring agents – tartazine, β- adregenic

antagonists, sulfating agent.

Aspirin – sensitive syndrome affects adults through seen in childhood.

The problem usually begins with perennial vasomotor rhinitis that is followed

by a hyper plastic rhino sinusitis with nasal polyps, progressing to asthma.

Indomethacin, fenoprofen, naprocen, zonepirae sodium, ibuprofen, mefanamic

acid and phenylbutazone are particularly important.

β- Adrenergic antagonist regularly obstructs the airway in asthmatics. In

fact, the local use of β- blockers in the eye for the treatment of glaucoma has

been associated with worsening asthma.

Sulfating agents can produce acute airway obstruction in sensitized

individuals. Exposure usually follows ingestion of food and beverages

containing these compounds. e.g. – salads, fresh fruit, potatoes, shell fish &

wine.

3. Environment and Air pollution

Environmental causes of asthma are usually related to climatic

conditions that promote the concentration of atmospheric pollutants and

antigens. These conditions tend to develop heavily industrial or densely

populated urban areas and frequently associated with thermal inversion or other

situation that cause stagnant air masses. The air pollutants known to have this

effect are ozone, nitrogen dioxide & sulphur dioxide.

4. Occupational factors

Occupation – related asthma is a significant health problem and acute

and chronic airway obstructions have been reported to follow exposure to a

large number of compounds used in many types of industrial process.

Broncho constriction can result from working with or being exposed to

metal salts, wood and vegetable dust, husk of grains, flour, castor bean, gum

acacia, karay gum, tragacanth, pharmaceutical agents e.g. antibiotics,

piperazine and cimetidine, industrial chemicals and plastics, biological

enzymes, laundry detergents and pancreatic enzymes, animal & insect dusts,

serum and secretions.

There seems to be three underlying mechanisms

1. In some cases, the offending agent results in formation of significant

IgE.

2. Substances cause direct liberations of broncho constrictor substances.

3. Substances cause direct or reflex stimulation of the airway of latent of

frank asthmatics.

5. Infection

Respiratory infections are the most common of the stimuli that evoke

exacerbations of asthma. In young children, the most important infectious

agents are respiratory syntical virus and para influenza virus. In older children

and adults rhino virus and influenza virus predominate as pathogens.

Streptococcus pneumoniae, H.influenza and viruses are responsible for

infection.

Simple colonization of the tracheo bronchial tree is insufficient to evoke

acute attacks & attack of asthma occurs only when the symptoms of an ongoing

respiratory tract infection are having been present. The mechanism by which

viruses induce exacerbations of asthma may be related to the production of T

lymphocyte derived cytokines that potentiate the infiltration of inflammatory

cell into already susceptible airways.

6. Exercise

Exercise is one of the most common precipitating factors in acute

episodes of asthma. Exercise probably invokes broncho spasm to some extent

in every asthmatic patient, and in some it is the only trigger that produces

symptoms. The mechanisms, by which exercise produce obstruction, may be

related to a thermally produced hyperthermia and engorgement of the

microvasculature of the bronchial wall and doesn’t appear to involve smooth

muscle contraction.

7. Emotional Stress

Psychological factors can interact with the asthmatic diasthesis to

worsen or ameliorate disease process. Changes in airway caliber seem to be

mediated through modification of nasal efferent activity, but endorphins also

may play a role.

8. Food and Drink

Atopic asthmatics may occasionally notice that their symptoms are

provoked by certain foods or drinks and it is worth enquiring of all asthmatic

patients whether they have notices such as association.

The food most frequently suspected the milk, eggs, fish, cereals, nuts

and chocolates. Preservatives such as benzoates, sodium nitrite, and sodium

metabisulphite, anti oxidants, dyes such as tartarzine, flavorings may be found

in many food and may provoke asthma. Red wines contain a number of

congeners which give them their distinctive flavors but which also may

provoke attacks of asthma.

9. Smoking

Smokers appear to be at greater risk of developing asthma and have a

higher prevalence of hyper-reactivity. Children of smokers also seem to have

an increased risk of developing wheeze.

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