Chronic Cough in Adults

Chronic cough is defined as a cough lasting more than 8 weeks. It sits at the end of a duration-based classification that also includes acute cough (under 3 weeks, usually infectious and self-limited) and subacute or postinfectious cough (persisting after an upper respiratory infection but usually resolving before 8 weeks). Cough receptors are distributed throughout the upper and lower respiratory tract and beyond, which gives chronic cough an unusually broad differential diagnosis — but in a nonsmoker with a normal chest x-ray who is not taking an angiotensin-converting enzyme (ACE) inhibitor, the cause is upper airway cough syndrome, cough-variant asthma, GERD-related cough, or nonasthmatic eosinophilic bronchitis in the large majority of cases.^[1][2] The core management principle is diagnostic, not symptomatic: chronic cough responds best to therapy directed at its underlying cause, and reaching for a nonspecific antitussive before that cause is identified risks masking or delaying the diagnosis of something that needs its own treatment — occasionally something serious.^[3]

How chronic cough actually presents

Chronic cough itself is a single symptom with few distinguishing features on its own — dry or productive, its pattern (worse at night, with meals, with exertion, with position change), and its associated symptoms are what point toward a specific cause rather than the cough itself. A careful history aimed at eliciting those associated symptoms is the single most useful diagnostic tool.

Clues that point toward a specific cause

• Postnasal drainage, throat clearing, nasal congestion or discharge, and a cobblestone appearance of the oropharyngeal mucosa point toward upper airway cough syndrome (UACS, formerly called postnasal drip syndrome).
• Wheeze, chest tightness, or a personal/family history of atopy point toward cough-variant asthma — though classic asthma features are often absent, and cough may be the only symptom.
• Heartburn, regurgitation, or a cough that is worse after meals or when lying flat suggests GERD-related cough — though up to half of GERD-related chronic cough occurs without typical reflux symptoms, so its absence does not rule this out.
• A dry, nonproductive cough beginning anywhere from hours to months after starting an ACE inhibitor, with no other predisposing factor, suggests drug-induced cough — this is a class effect of every ACE inhibitor.
• Minimal or no wheeze with a normal spirometry and negative bronchial challenge test, often in a postinfectious setting, suggests nonasthmatic eosinophilic bronchitis (NAEB).

Cough hypersensitivity

Many patients with chronic cough — whether an underlying cause has been found or not — describe a pattern of exaggerated sensitivity to low-level triggers that would not provoke cough in most people: cold air, perfume, smoke, talking, or laughing. This clinical pattern, termed cough hypersensitivity syndrome, reflects hypersensitivity of the airway's afferent (sensory) nerves combined with central augmentation of the cough reflex, and is the physiologic basis for the neuromodulator therapies used in refractory and unexplained chronic cough.^[1]

• Current or past tobacco or e-cigarette (vaping) use, including cannabis smoking.
• Use of an ACE inhibitor — a class effect, not specific to any one agent.
• Occupational or environmental exposure to irritants or allergens.
• Personal or family history of atopy, allergic rhinitis, or asthma.
• Known or suspected GERD, or risk factors for it (obesity, hiatal hernia).
• Use of a statin or a beta-blocker — both are recognized, less common medication-related causes of chronic cough; a beta-blocker can also aggravate underlying asthma.
• Obstructive sleep apnea — an increasingly recognized association, with some patients responding to continuous positive airway pressure therapy.

History and physical examination

A structured history should specifically cover: cough duration and its variation over the day; onset, severity, and character (wet versus dry); triggers; nocturnal symptoms and impact on quality of life; smoking/vaping history (tobacco and cannabis); current medication use, especially ACE inhibitors and, less commonly, statins or beta-blockers; symptoms of asthma, upper airway disease, and GERD; occupational and environmental exposures; and personal or family history of atopy or asthma. Examination should include the nasal cavities, oropharynx, and ear canals in addition to the respiratory and cardiac systems.^[1]

Objective testing

• Chest x-ray and complete blood count in essentially every patient with chronic cough.
• Spirometry, pre- and post-bronchodilator, to evaluate for asthma and COPD.
• Methacholine (or other bronchial) challenge testing to detect airway hyperresponsiveness when asthma is suspected but spirometry is nondiagnostic — a positive test supports but does not by itself confirm cough-variant asthma, since false-positive challenge tests occur.
• For suspected GERD: ambulatory pH monitoring is the most sensitive available test but still predicts acid-related cough imperfectly; impedance monitoring can detect nonacid reflux but is not widely available; upper GI series and endoscopy are frequently normal and are not first-line for this indication. A positive response to a therapeutic trial of acid suppression (an H2-receptor antagonist or a PPI) is a practical, widely used way to support the diagnosis when reflux-related cough is suspected.
• For suspected NAEB: induced sputum eosinophilia, exhaled nitric oxide (where available), and a response to inhaled corticosteroids, in a patient with normal spirometry, a normal chest x-ray, and negative bronchial challenge testing.
• Sputum for acid-fast staining and culture, sputum cytology, and CT chest for any patient with hemoptysis — refer to respirology for fibre-optic bronchoscopy.
• Reserve CT chest and bronchoscopy for patients with no identified cause after initial evaluation and after cough remains refractory to empiric therapeutic trials for the common causes, or when a red flag or a specific clinical suspicion (malignancy, chronic infection such as tuberculosis, interstitial lung disease, bronchiectasis, foreign body aspiration, occult left heart failure, irritable larynx syndrome) points toward a less common cause.

Table 1 — Common causes of chronic cough: clinical features and investigations

Reserve the "potential investigations" column for patients with no overt cause identified on initial evaluation, or cough that is refractory to an adequately conducted empiric trial for the most likely common cause.

• Identify the specific underlying cause (or causes — more than one can coexist) and select therapy directed at that cause, rather than defaulting to nonspecific cough suppression.
• Minimize adverse effects of therapy, particularly of empiric trials that may ultimately prove unnecessary.
• Avoid nonspecific cough-suppression therapy that could delay diagnosis of a curable underlying cause.
• Prevent complications of persistent coughing itself — rib fracture, syncope, sleep disruption, aggravation of stress urinary incontinence, exercise intolerance, vomiting, epistaxis, and ocular injury or hemorrhage.
• Ensure that uncommon but serious causes, particularly lung cancer, are not missed by premature closure on a benign diagnosis.

• Advise cessation of all tobacco products and e-cigarettes/vaping in every current user — a temporary worsening of cough can occur after quitting and may persist for several months; counsel patients about this in advance so it is not mistaken for treatment failure.
• Advise avoidance of known allergens and environmental/occupational irritants.
• For GERD-related cough: weight loss if overweight, avoidance of specific trigger foods/beverages, avoiding meals late in the evening, and nocturnal elevation of the head of the bed.
• For UACS from chronic rhinosinusitis or nonallergic rhinitis: regular nasal saline irrigation or spray is a genuine first-line measure, not just an adjunct, and is safe for ongoing use.
• Consider multimodality speech-language pathology therapy for laryngeal dysfunction and for unexplained chronic cough generally.
• Consider suggestion therapy (hypnosis) or behavioural therapy for psychogenic (habit) cough — an uncommon presentation and a diagnosis of exclusion, not a first-line assumption.
• Evaluate for obstructive sleep apnea in patients with suggestive symptoms; continuous positive airway pressure therapy has been associated with cough improvement in this subgroup.

Pregnancy

Data on the prevalence, causes, and treatment of chronic cough specifically in pregnancy are limited, and several of the common causes can be worsened by pregnancy — most notably GERD, given smooth-muscle relaxation and increased abdominal pressure. Start with lifestyle modification and antacids for GERD-related cough in pregnancy; H2-receptor antagonists have extensive reassuring safety experience in pregnancy, and PPI data, while less extensive, are also reassuring (see the Gastroesophageal Reflux Disease chapter for specific agent selection and dosing). The therapeutic approach to UACS and to cough-variant asthma is minimally changed by pregnancy — short-acting bronchodilators and inhaled corticosteroids are used per the Asthma in Adults and Adolescents chapter, and most intranasal corticosteroids are considered safe in pregnancy, though triamcinolone should be avoided given a possible association with congenital malformations; first-generation oral antihistamines are considered safe in pregnancy, and nasal saline is safe and effective throughout pregnancy and breastfeeding.^[11] Avoid an oral decongestant (pseudoephedrine) in the first trimester specifically — case-control data have linked first-trimester oral decongestant use to a small increase in specific birth defects, including gastroschisis; a short-acting intranasal decongestant is preferred if a decongestant is genuinely needed early in pregnancy. If an antitussive is needed, dextromethorphan is considered compatible with pregnancy and breastfeeding, while morphine and codeine carry recognized fetal and neonatal risks and should be avoided as a routine choice.

Breastfeeding

Antacids, H2-receptor antagonists, and PPIs (particularly omeprazole and pantoprazole) are considered safe during breastfeeding — see the Gastroesophageal Reflux Disease chapter. Most intranasal corticosteroids and nasal saline are safe in breastfeeding. Pseudoephedrine can reduce milk supply and should be used cautiously, favouring a short course or an intranasal alternative. Opioid antitussives (morphine, codeine) carry recognized infant toxicity risk during breastfeeding and should be avoided when an alternative is reasonable.

Older adults

Avoid routine use of first-generation antihistamines (e.g., diphenhydramine) for UACS in older adults — the 2023 AGS Beers Criteria specifically recommend against this class in this population given markedly increased anticholinergic toxicity, confusion, delirium, and fall risk.^[4] Use pseudoephedrine cautiously given increased cardiovascular sensitivity in this population. Gabapentin, pregabalin, and opioid antitussives all carry higher sedation and fall risk in older adults — start at the low end of the dose range and titrate more slowly.

Renal impairment

Gabapentin and pregabalin are both renally cleared and require dose reduction in renal impairment — consult product-specific renal dosing before starting or continuing either agent as chronic kidney disease progresses. Codeine and morphine active metabolites can accumulate in significant renal impairment, increasing the risk of oversedation and respiratory depression — use the lowest effective dose with close monitoring, or avoid.

Pediatrics

This chapter covers chronic cough in adults specifically; the diagnostic and treatment approach in children differs meaningfully and is not addressed here. First-generation antihistamines are not recommended in children under 6 years of age. Opioid-containing cough and cold products (codeine, hydrocodone) are restricted by Health Canada to patients 18 years of age and older and must not be used in children or younger adolescents.

• ACE inhibitor withdrawal trial: reassess at 1 week and again at 4 weeks — most patients improve within 1 week, but allow the full 4 weeks before concluding the ACE inhibitor was not the cause.
• PPI trial for GERD-related cough: assess response no sooner than 8 weeks (see the Gastroesophageal Reflux Disease chapter).
• Inhaled corticosteroid trial for NAEB: assess response at 2-4 weeks; escalate dose or add montelukast if incomplete.
• Gabapentin for refractory/unexplained chronic cough: monitor closely for sedation, ataxia, and other adverse effects at each dose titration; formally reassess efficacy at 6 months, and taper toward the lowest effective dose or discontinuation if the cough has responded and remained stable.
• Morphine trial: response, when present, is typically rapid — reassess at 1-2 weeks and discontinue if no benefit has occurred by then, rather than continuing to escalate the dose.
• At every follow-up, confirm that the cough attributed to a given cause has genuinely resolved or substantially improved, not simply that a course of therapy was completed — an incompletely treated cause is a common reason for apparent treatment failure.

1. Confirm the empiric trial that was tried was actually adequate — full recommended dose, for the full recommended duration (e.g., a genuine 4-week ACE inhibitor washout, a genuine 8-week PPI trial, a genuine 2-4 week inhaled corticosteroid trial) — before concluding it failed.
2. Reconsider whether more than one cause is present. Coexisting causes are common; continue any therapy that produced partial improvement while investigating for an additional contributing cause, rather than discontinuing it.
3. Move to the next most likely cause in the diagnostic sequence rather than declaring the cough unexplained after only one trial.
4. If the common causes have been adequately investigated and treated or excluded, and no red flag is present, proceed to less common causes (obstructive sleep apnea, chronic infection, structural/interstitial lung disease, occult heart failure, irritable larynx syndrome, foreign body) with CT chest and consideration of bronchoscopy referral.
5. If no cause is found after a complete evaluation (unexplained chronic cough) or an identified cause does not respond to appropriate cause-directed treatment (refractory chronic cough), refer to a cough specialty clinic and consider a neuromodulator approach targeting cough hypersensitivity — gabapentin first, then pregabalin or low-dose sustained-release morphine.
6. For a patient responding well to neuromodulator therapy, attempt a taper to the lowest effective dose, or a trial off therapy, at around 6 months.

• Starting an antitussive or mucolytic before completing a cause-directed workup — mucolytics in particular have no proven role in chronic cough, and premature symptom suppression can delay diagnosis of a treatable (or serious) cause.
• Missing an ACE inhibitor as the cause because the cough started long after the drug was initiated — onset can occur anywhere from hours to months after starting the drug, so temporal distance alone does not rule it out.^[7]
• Stopping an ACE inhibitor trial before 4 weeks and concluding it was not the cause, when resolution can take up to that long even though most patients improve within 1 week.
• Starting empiric PPI therapy for chronic cough when GERD investigations are genuinely negative — current evidence does not support this, and it exposes the patient to unnecessary long-term acid suppression.^[5]
• Treating a red flag (hemoptysis, significant smoking history with a new/changed cough pattern, systemic symptoms) with an empiric trial instead of urgent imaging or referral.
• Routine use of a first-generation antihistamine in an older adult for UACS, rather than a nonsedating alternative or an intranasal corticosteroid.
• Prescribing or recommending a codeine- or hydrocodone-containing product to a patient under 18 years of age.
• Assuming a patient with unexplained chronic cough has no treatable option once initial testing is unrevealing — cough-hypersensitivity-targeted neuromodulator therapy (gabapentin first-line) is a real, evidence-based option, not a dead end.
• Overestimating the efficacy of over-the-counter cough suppressants for chronic cough specifically — trial evidence for classic antitussives in this setting is limited, and they have, at most, a minor adjunctive role.

How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.

Upper airway cough syndrome — intranasal corticosteroids

First-line for UACS regardless of allergic or nonallergic cause; also first-line for chronic-rhinosinusitis-driven UACS alongside nasal saline.

Upper airway cough syndrome — oral antihistamines and decongestant

Nonsedating antihistamines are preferred, particularly in older adults; the first-generation antihistamine plus decongestant combination is reserved for empiric therapy when the specific UACS cause cannot be identified.

Cough-variant asthma and GERD-related cough

Managed per the Asthma in Adults and Adolescents chapter and the Gastroesophageal Reflux Disease chapter respectively — dosing is not repeated here to avoid duplicating or drifting from that chapter's guidance.

Nonasthmatic eosinophilic bronchitis (NAEB)

A 2-4 week trial is both diagnostic and therapeutic; a positive response supports the diagnosis.

ACE inhibitor-induced cough — substitution agents (angiotensin receptor blockers)

Not associated with cough. Select the agent and target dose based on the original indication (hypertension, heart failure, post-MI, diabetic nephropathy) that required renin-angiotensin system blockade.

Refractory or unexplained chronic cough — neuromodulators

Reserved for confirmed refractory or unexplained chronic cough after red flags, ACE inhibitor use, and the common causes above have been addressed. Gabapentin is first-line; pregabalin and morphine are alternatives with a less favourable adverse-effect profile.

Nonspecific antitussives

Limited role in chronic cough overall; reserve for short-term, adjunctive symptom relief (e.g., to enable sleep) once a cause-directed workup is underway, never as a substitute for it. Use with caution in productive cough, since suppressing an effective cough can cause mucus retention. Not useful for ACE inhibitor-induced cough.