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A cough is considered chronic if it persists for longer than 3 weeks. In the nonsmoker with a chronic cough who is not taking angiotensin-converting enzyme (ACE) inhibitors and who has a normal chest radiograph, one of three diagnoses is likely: postnasal drip syndrome (PNDS), asthma, or gastroesophageal reflux disease (GERD). Many patients have more than one cause (1,2,3 and 4).

I. Cough due to postnasal drip.

Singly or in combination with other conditions, PNDS is the most common cause of all chronic cough. This syndrome is due to a variety of upper airway conditions including the common cold, allergic rhinitis, vasomotor rhinitis, postinfectious rhinitis, rhinitis due to environmental or medication irritants, and acute and/or chronic (bacterial) sinusitis. These various entities overlap and may best be called rhinosinusitis.

There are no definitive diagnostic criteria for PNDS. A favorable response to therapy is the best way to make the diagnosis. Allergy testing can be helpful in some patients, but positive skin tests do not prove that allergy is the cause. Direct nasolaryngoscopy may also be useful. A four-view sinus radiograph or, preferably, a sinus coronal CT scan will show the presence of chronic sinusitis, provided it is obtained at least 6 weeks after an acute episode to avoid false positives (3).

Empirical therapy for PNDS should be tried before beginning an extensive diagnostic workup. For vasomotor or postinfectious rhinitis, the older generation of antihistamine/decongestants has been shown to be effective (4). To reduce side effects, initiate therapy at bedtime. The newer generation antihistamines, either alone or in combination with pseudoephedrine, have not been shown to reduce cough associated with the common cold. The use of ipratropium or azelastine nasal sprays (2 sprays in each nostril bid) may also be effective. For PNDS due to allergic rhinitis, all oral antihistamines, nasal cromolyn, and nasal steroids are effective. Nasal steroids are the drug of choice and their administration may be necessary for at least 3 months. Antibiotics used to treat chronic sinusitis include amoxicillin (Amoxil) 500 mg tid, trimethoprim–sulfamethoxazole (Septra DS) bid, or erythromycin (Erythromycin Filmtab) 250 mg qid (all for 3 weeks); or azithromycin (Zithromax), two 250-mg tablets on day 1, followed by one tablet daily on days 2–5, with the regimen repeated after 1 week off. (See Chapter 8.5.) Nasal washes may also be helpful.

II. Cough variant asthma. (See also Chapter 10.1.)

This entity is easily overlooked because breathlessness or wheezing may be minimal. A viral respiratory illness or a bacterial or atypical bronchitis may initiate this cough variant asthma. This postinfectious type of cough variant asthma is a common clinical occurrence. Seasonal or specific allergies can also precipitate this syndrome. The cough is usually nonproductive and occurs throughout the day and night.

III. Cough due to GERD

Many patients with cough have typical gastrointestinal (GI) symptoms, such as sour taste, heartburn, and regurgitation. However, some have no GI complaints, and the reflux is only discovered upon workup (5).

In patients with typical GI symptoms or those in whom a GI cause is suspected, 24-hour ambulatory esophageal pH monitoring is the best test. But first ask about a time of cought, if it is bedtime, you should think, GERD.

The H2 antagonists, such as cimetidine (Tagamet) 800 mg qd or ranitidine (Zantac) 150 mg bid, are the mainstays of drug therapy (4). As some patients' symptoms may not improve for 2–3 months, long-term treatment may be necessary. Interestingly, both cough symptoms and reflux continue to be suppressed for more than 6 weeks after H2 blockers are stopped. Proton pump inhibitors, such as omeprazole (Prilosec) 20 mg qd to 40 mg bid, are also used and may be tried if there is no response to or poor toleration of H2 blockers. It is difficult to predict which patients will respond to therapy. Antireflux surgery, now frequently done by laparoscopy, is reserved for patients with continued symptoms who fail medical therapy, including proton pump inhibitors.

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