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A 12-year-old boy presents with complaints of chronic cough and inability to keep up with his schoolmates during
physical education class. The patient's mother states that he has just recovered from his fourth bout of
pneumonia in the past 5 months. On examination, digital clubbing, hyperresonance to percussion, and basilar
crackles are noted. The boy's sweat chloride concentration is 87 mEq/L. Which of the following agents would
most likely serve to alleviate his chronic signs and symptoms?
A. Dextromethorphan (PO)
B. Ipratropium (aerosolized)
C. N-acetylcysteine (aerosolized)
D. Pentamidine (aerosolized)
E. Vancomycin (IV)
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Explanation:
The correct answer is C. The patient is presenting with signs and symptoms of cystic fibrosis (CF). CF is an
autosomal recessive disorder of the exocrine glands. The pulmonary manifestations include acute and chronic
bronchitis, bronchiectasis, chronic bouts of pneumonia, hemoptysis, and cor pulmonale, which can occur late in
the disease. Other common findings include chronic cough, exercise intolerance, recurrent respiratory
infections, digital clubbing, increased anteroposterior diameter, and basilar crackles. If the pilocarpine sweat
test reveals sodium and chloride levels greater than 80 mEq/L, a diagnosis of CF can be made. The primary
goals of treatment include thinning the mucus secretions, keeping the airways open, and treating recurrent
infections. Thinning of mucus can be achieved with mucolytics such as N-acetylcysteine. N-Acetylcysteine
(Mucomyst) splits the disulfide linkages between these mucoproteins, resulting in a decrease in mucous
viscosity. It is indicated as adjuvant therapy in the treatment of abnormal viscid or inspissated mucus secretions
in CF, chronic lung disease, post-traumatic chest complications, and atelectasis secondary to mucus
obstruction. Inhaled bronchodilators are used to open the airways. Furthermore, prednisone has been shown to
increase pulmonary function and increase body weight. The definitive treatment is lung transplantation.
Dextromethorphan (choice A), a cough suppressant, is contraindicated in patients with CF since it will prevent
the removal of mucus from the lungs.
Ipratropium (choice B) is an anticholinergic that will cause a drying and thickening of the mucus in this patient;
therefore, it is contraindicated.
Pentamidine (aerosolized) (choice D) is an antiprotozoal agent primarily used in the treatment of Pneumocystis
carinii pneumonia in HIV-infected patients.
Vancomycin (choice E) is an anti-infective agent used in the treatment of life-threatening, gram-positive
infections.
