Respiratory Drugs and Medications Q 19

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When administering the methylxanthine theophylline, the nurse can expect:

  

     A. Decreased pulmonary function

     B. Increased pulmonary function

     C. Increased residual volume

     D. Decreased tidal volume

    

    

Correct Answer: B. Increased pulmonary function

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Theophylline will improve ventilation so there will be an overall improvement of pulmonary measurements. Theophylline is a drug derived from methylxanthine (a purine derivative) and has smooth muscle relaxant, bronchial dilation, diuretic, cardiac and central nervous system (CNS) stimulant activities. Other choices are the opposite of what will actually occur with theophylline administration.

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Option A: Theophylline relaxes the smooth muscles located in the bronchial airways and pulmonary blood vessels. It also reduces the airway responsiveness to histamine, adenosine, methacholine, and allergens.

Option C: It acts as a competitive nonselective phosphodiesterase inhibitor (inhibiting type III and type IV phosphodiesterase), which increases the concentration of intracellular cAMP, activates protein kinase A, inhibits TNF-alpha and leukotriene synthesis, and also decreases inflammation and innate immunity.

Option D: It is also a nonselective adenosine receptor antagonist. It acts on A1, A2, and A3 receptors with almost the same affinity, and this possibly explains the cardiac effects of theophylline. Adenosine-mediated channels also increase the contraction force of diaphragmatic muscles by enhancing their calcium uptake.

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