Last winter and early spring (before COVID-19), my office received many calls from patients complaining about a cough that just wouldn’t go away. There was an upper respiratory virus going around that caused people to feel sick for weeks. Many asked for more antibiotics, which wouldn’t have helped. Eventually it subsided. Sometimes, however, a cough may last for many months, even years. The term for this is refractory chronic cough (RCC). Today I would like to discuss the causes, work-up, and treatment of RCC.
The most common causes of RCC are the use of an angiotensin-converting enzyme inhibitor, or ACE inhibitor (i.e. lisinopril), which is used to treat high blood pressure, asthma, chronic obstructive pulmonary disease (COPD, aka emphysema), gastroesophageal reflux disease, or GERD, and upper airway cough syndrome (UACS), usually caused by a post-nasal drip or sinus infection. Less common causes of RCC include aspiration of a foreign body, pneumonia, lung cancer, tuberculosis, bronchitis, sarcoidosis, and idiopathic pulmonary fibrosis (scarring and thickening of the lungs).
When searching for the cause of RCC, several questions need to be asked before ordering any tests. First and obviously, is the patient on an ACE inhibitor? Does the patient smoke or does the patient have an occupational exposure to dust or allergens? Does the patient have heartburn or symptoms of GERD, chronic nasal congestion, or wheezing and shortness of breath? And is there any hemoptysis (coughing up blood), chest pain, or weight loss which might point to lung cancer, especially with a smoking history. Following a physical exam, the first test would be a chest X-Ray. Spirometry, which measures lung volumes and airflow, is helpful in diagnosing asthma and COPD. If there is still no cause found for the cough, nasal endoscopy to diagnose UACS and laryngoscopy are helpful. Likewise, upper endoscopy can reveal the presence of GERD. Several studies have found that about 75% of people with a chronic cough attributable to GERD had no gastrointestinal symptoms.
Infrequently, the work-up and testing reveals no obvious cause of RCC. Sometimes this unexplained chronic cough is thought to come from the nervous system, called a neurogenic cough. In this case, a neuromodulator like gabapentin, pregabalin, amitriptyline, tramadol, or baclofen can be used. Studies have shown them to be about 75% effective for a neurogenic cough. Often, behavioral therapy by a speech pathologist can help suppress the cough, as can laryngeal nerve blocks and the use of botulinum toxin injections. Lastly, narcotics, like morphine and codeine, have a long history of use as a centrally acting cough suppressant, although, given today’s opioid epidemic, introducing the patient to the chronic use of a narcotic can be a very slippery slope.
Lastly, a cough that lasts for more than a week or two should never be ignored, although unexplained chronic cough, or RCC, is common and often its cause remains elusive.
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By Peter Galvin, MD