2nd phase of bronchial asthma can be prevented by:

Ans: b (Steroids) Ref: OP Ghai, 6th ed, p. 354Second phase or late phase of bronchial asthma is inhibited by premedication with steroid and it suggests that airway narrowing is mainly due to an inflammatory reaction and mucosal oedema. This phase is not prevented by premedication with a2 agonists.Inhalation of an allergen leads to a biphasic response with early and late reaction ultimately causing bronchoconstriction.Early reactionIt starts within 10 minutes of exposure to the allergenit is characterized by release of histamine, leukotrienes C, D. E. prostaglandins, platelet activating factor and bradykinin from mast cells that follows the interactions of allergen with specific mast cell bound IgE.This phase is inhibited by a2 agonist drugs.Late phaseIt occurs 3-4 hours later with peak at 8-12 hours.This phase is inhibited by steroids and cannot be prevented by a2 agonist drugs.This phase presents as clinical asthma.