A 32-year-old woman complains of a "nagging" dry cough over the last 8 weeks. The cough is present during the day and awakens her at night. There is no associated shortness of breath, chest pain, or wheezing. The patient's past medical history is significant for chronic rhinorrhea and an occasional itching skin rash. She takes no medications. Chest x-ray shows no abnormalities. One week of treatment with chlorpheniramine significantly improves her symptoms. Decrease in which of the following is most likely responsible for her symptom relief?

Question

A 32-year-old woman complains of a "nagging" dry cough over the last 8 weeks.  The cough is present during the day and awakens her at night.  There is no associated shortness of breath, chest pain, or wheezing.  The patient's past medical history is significant for chronic rhinorrhea and an occasional itching skin rash.  She takes no medications.  Chest x-ray shows no abnormalities.  One week of treatment with chlorpheniramine significantly improves her symptoms.  Decrease in which of the following is most likely responsible for her symptom relief?

Quizplus · Accepted Answer

The 3 most common causes of chronic cough (lasting >8 weeks) are upper-airway cough syndrome (postnasal drip), asthma, and gastroesophageal reflux disease (GERD). Upper-airway cough syndrome is caused by rhinosinus conditions including allergic, perennial nonallergic, and vasomotor rhinitis; acute nasopharyngitis; and sinusitis. Cough is caused by mechanical stimulation of the afferent limb of the cough reflex in the upper airway in these conditions. Based on her history, this patient's dry cough is most likely due to postnasal drip associated with allergic rhinitis. The diagnosis is confirmed by the improvement of the nasal discharge and cough with the use of first-generation antihistamines. Chlorpheniramine is a specific H1 antihistaminic receptor blocker that reduces the action of histamine on H1 receptors, decreasing the allergic response. In addition to blocking H1 histamine receptors, chlorpheniramine exhibits anti-inflammatory effects by blocking histamine release from mast cells and limiting the secretory response to inflammatory cytokines. (Choice A) Acid reflux can irritate the cough reflex and is also a common cause of chronic cough. Empiric therapy of GERD includes dietary and lifestyle modifications and proton pump inhibitors, which suppress stomach acid secretion. Antihistamines would not help the cough associated with GERD. (Choices B and D) Asthma can also cause chronic cough. It is characterized by variable and recurring symptoms, airflow obstruction, bronchial inflammation, and airway hyperreactivity. Empiric treatment involves inhaled corticosteroids, which reduce airway inflammation, and β-adrenergic agonists, which dilate bronchial smooth muscle. Antihistamines have no role in asthma management. (Choice C) About 5%-20% of patients treated with an angiotensin-converting enzyme (ACE) inhibitor develop dry cough due to ACE inhibition causing decreased degradation of bradykinin and substance P. Accumulation of these substances causes cough. Cough improves only with discontinuation of an ACE inhibitor and not with antihistamines. Educational objective: The 3 most common causes of chronic cough are upper-airway cough syndrome (postnasal drip), asthma, and gastroesophageal reflux disease. The diagnosis of upper-airway cough syndrome is confirmed by the elimination of nasal discharge and cough with the use of H1 histamine receptor antagonists. References: Chronic upper airway cough syndrome secondary to rhinosinus diseases (previously referred to as postnasal drip syndrome): ACCP evidence-based clinical practice guidelines. (http://www.ncbi.nlm.nih.gov/pubmed/16428694)

A 32-Year-Old Woman Complains of a "Nagging" Dry Cough Over