Acute Bronchitis

Acute bronchitis is the acute onset of cough, with or without sputum production, present for less than 3 weeks, caused by transient inflammation of the trachea and major bronchi.^[1] Viral infection accounts for over 90% of cases; there is no strong evidence that a distinct "acute bacterial bronchitis" exists in adults without underlying lung disease. No routine pharmacologic treatment is indicated — management is supportive, and antibiotics do not meaningfully change the course of illness in an otherwise healthy patient.^[2] Symptoms resolve in a median of 18 days, but cough can persist up to 8 weeks in a substantial minority; for cough lasting longer than 8 weeks, manage per the Chronic Cough in Adults pathway.

Typical presentation

Acute cough (<3 weeks), productive or dry, often preceded or accompanied by nasal congestion, mild constitutional symptoms, and sometimes wheezing. Green or discoloured sputum reflects peroxidase release from leukocytes and indicates inflammation, not necessarily bacterial infection — it is not, on its own, a reason to prescribe an antibiotic.

Course

Transient bronchial hyper-responsiveness is the predominant mechanism underlying persistent cough. Cough resolves in a median of 18 days; up to 50% of patients still have cough at 3 weeks, and cough can persist up to 8 weeks in about half of cases due to viral-triggered airway hyper-reactivity, not ongoing infection.

• Recent upper respiratory tract infection or known exposure to a person with a similar illness.
• Tobacco or e-cigarette use, or second-hand smoke exposure — both a risk factor for the presentation and a target for counselling regardless of outcome.
• Known pertussis outbreak in the area, incomplete immunization, or recent travel to an outbreak area.
• Underlying pulmonary disease (asthma, COPD) — changes the differential and management, not a risk factor for acute bronchitis itself.
• Occupational or environmental exposure to inhaled irritants.

Distinguishing acute bronchitis from its mimics

Acute bronchitis is a diagnosis of exclusion at the bedside — there is no confirmatory test. The entire clinical task is ruling out the conditions below, all of which are managed completely differently.

History

• Cough character (productive or dry), duration, and trajectory — improving, static, or worsening.
• Sputum colour — discoloured sputum reflects inflammation, not necessarily infection, and should not by itself drive an antibiotic decision.
• Associated symptoms: nasal congestion, mild constitutional symptoms, wheeze, tachypnea, respiratory distress, hypoxemia.
• Vaccination history, travel history, tobacco/e-cigarette use, second-hand smoke exposure, underlying pulmonary disease, and comorbidities.
• In children with a prolonged cough, consider reactive airway disease instead of acute bronchitis (see Asthma in Infants and Children). Consider pertussis specifically when a spasmodic cough pattern, a known local outbreak, or prior travel to an outbreak area is elicited.

Examination

• Vital signs: heart rate, respiratory rate, oral temperature — a normal heart rate (<100/min), normal respiratory rate (<24/min in adults), oral temperature <38°C, and absence of localized chest findings together carry a 96-100% negative predictive value for pneumonia in adults, eliminating the need for chest x-ray.
• Auscultation for localized findings (crackles, bronchial breath sounds, dullness to percussion) that would suggest pneumonia instead.

Investigations

• There is no role for routine chest x-ray, viral culture, serologic assays, sputum culture, Gram stain, or spirometry in uncomplicated acute bronchitis.
• Consider COVID-19 testing per current local testing guidance.
• Procalcitonin can help distinguish bacterial from other infection in cases of genuine diagnostic uncertainty, but availability is a major practical limitation.

• Rule out serious illness — pneumonia, an asthma/COPD exacerbation, pertussis.
• Minimize symptoms with supportive care.
• Limit unnecessary antibiotic use.

Nonpharmacologic care is the mainstay of management, not an adjunct to it:

• Patient education on the expected course — a 2-3 week "chest cold," with cough occasionally persisting up to 8 weeks — sets expectations and is itself an evidence-based intervention.
• Avoidance of tobacco smoke and other pulmonary irritants.
• Strict hand hygiene and covering coughs to limit transmission.
• Increased humidity may help reduce cough.
• Increased fluid intake may prevent dehydration in children; evidence in adults is insufficient to recommend this specifically, though general hydration is reasonable.
• Rest to support recovery.

Natural health products

• Honey was more effective than diphenhydramine, salbutamol, and placebo (though not better than dextromethorphan) for cough frequency and severity in a Cochrane review of adults and children.^[5] Use only pasteurized honey, and only in immunocompetent children over 1 year of age, because of the risk of infant botulism below that age.
• Pelargonium sidoides (umckaloabo) has shown possible symptom benefit in some low-quality trials; it is generally well tolerated, though allergic skin reactions, GI upset, and liver toxicity have been reported. Evidence in children is emerging but currently insufficient to recommend routine use.
• There is insufficient evidence to recommend Chinese medicinal herbs, and no direct evidence for North American ginseng or Tropaeolum majus specifically in acute bronchitis.

Pregnancy

Manage supportively as in the nonpregnant patient. Fever, headache, and discomfort can be managed safely with acetaminophen. Avoid NSAIDs in the third trimester (risk of premature ductus arteriosus closure) and after 20 weeks' gestation (potential reduction in amniotic fluid). If cough control is needed, dextromethorphan is reasonable; opioids should be used cautiously near term.

Breastfeeding

Health Canada and the FDA advise limiting codeine in breastfeeding patients because of a risk of CNS and respiratory depression in the infant from variable maternal metabolism to morphine; the interpretation of the underlying case reports remains debated, but the cautious approach is to avoid codeine while breastfeeding when an alternative is reasonable. Inhaled short-acting beta2-agonists are considered safe in pregnancy and breastfeeding, but the modest symptomatic benefit should be weighed against side effects before use.

Children

Opioid-containing cough and cold products (codeine, hydrocodone) are not recommended by Health Canada for anyone under 18 years of age.^[6] NSAIDs and acetaminophen should be used only in the presence of fever, not for cough itself. Persistent cough in a child may indicate reactive airway disease rather than acute bronchitis — reassess for asthma. Dextromethorphan is not recommended under 6 years of age.

Smokers

There is no evidence that people who smoke, but do not have underlying lung disease, benefit more from antibiotics than nonsmokers — smoking status alone is not a reason to prescribe.

Set expectations up front: average cough duration is 18 days, and up to 8 weeks in about half of patients, even though many feel substantially better within the first week. Follow up if symptoms have not started improving after 3 weeks from onset. Offer annual influenza vaccination to all patients over 6 months of age, and follow current NACI recommendations for pneumococcal and COVID-19 vaccination in high-risk groups as primary prevention for future episodes.

1. Reassess for a missed diagnosis — pneumonia, asthma/COPD exacerbation, or pertussis — rather than assuming this is simply a slow-resolving acute bronchitis.
2. For cough persisting beyond 3 weeks, actively reconsider the differential; for cough beyond 8 weeks, transition to the Chronic Cough in Adults pathway.
3. For frequent or recurrent bouts of "bronchitis," evaluate for underlying asthma, COPD, bronchiectasis, GERD, or a medication cause (e.g., ACE-inhibitor-induced cough).
4. If pertussis is suspected (paroxysmal cough, whoop, post-tussive vomiting, known exposure), obtain PCR/culture and notify public health rather than continuing symptomatic acute bronchitis management.

• Prescribing an antibiotic because sputum is discoloured — this reflects inflammation, not necessarily bacterial infection, and is not an indication on its own.
• Prescribing an antibiotic to satisfy a patient's expectation — patient satisfaction depends on the quality of communication, not on receiving a prescription.^[3]
• Ordering a chest x-ray, sputum culture, or spirometry routinely when vital signs and exam are reassuring — this adds cost and delay without changing management.
• Using a short-acting beta2-agonist routinely without evidence of airflow obstruction — no benefit, real adverse effects (NNH=2).^[7]
• Prescribing codeine- or hydrocodone-containing products to a patient under 18 years of age.
• Missing pertussis in a patient with a paroxysmal cough pattern, especially with a known local outbreak.
• Continuing to call it "bronchitis" when the real driver is unrecognized asthma, GERD, or an ACE inhibitor.

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.

Analgesics/antipyretics

For fever, headache, myalgia, or chest discomfort.

Antitussives

For sleep-disrupting or bothersome cough only — not for routine use.

Short-acting beta2-agonists

Not recommended for routine use — reserve for patients with wheeze, bronchial hyper-responsiveness, or FEV1 under 80% predicted; no benefit shown in children without airflow obstruction.

Natural health products

Modest evidence base; discuss expectations honestly with the patient.