Acute Bronchitis

Clinical Snapshot

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.

Recognize the Condition

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.

Etiology

Viral (>90%)

The dominant organisms vary by age — under 1 year: RSV, parainfluenza, coronavirus (including SARS-CoV-2); 1-10 years: parainfluenza, enterovirus, RSV; over 10 years: influenza, parainfluenza, RSV, rhinovirus, and less commonly adenovirus, coronavirus, enterovirus.

Bacterial (5-10%)

Only Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Bordetella pertussis/B. parapertussis have been shown to cause acute bacterial bronchitis. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis are not established causes of acute bronchitis in adults without underlying lung disease.

Noninfectious

Chemical and fume inhalational exposures, including tobacco and other pulmonary irritants — not well studied, but should be part of the history.

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.

Risk Factors

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.

Red Flags & Refer

Reconsider the diagnosis and investigate further if any of the following are present — these should prompt reassessment for pneumonia, an asthma/COPD exacerbation, pertussis, or another cause rather than continued management as uncomplicated acute bronchitis.

Oral temperature >38°C or heart rate >100/min (adults) — the best clinical predictors of pneumonia along with abnormal breath sounds.^[3]
Respiratory rate above age-specific thresholds in children (2-12 months: >60/min; 1-5 years: >40/min; >5 years: >20/min).
Localized findings on chest auscultation (crackles, bronchial breath sounds, dullness).
Stridor (consider foreign body aspiration, epiglottitis, or croup instead).
Respiratory distress or hypoxemia.
Spasmodic/paroxysmal coughing fits, an inspiratory whoop, or post-tussive vomiting (consider pertussis, especially with a known local outbreak or in an incompletely immunized patient).
Symptoms persisting beyond 3 weeks without improvement.

Assessment & Diagnosis

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.

Feature	Acute bronchitis	Community-acquired pneumonia	Asthma/COPD exacerbation	Pertussis
Vital signs	Normal — heart rate <100/min, respiratory rate <24/min (adults), oral temperature <38°C	Fever >38°C and/or tachypnea are the best clinical predictors	May have tachypnea, hypoxemia, accessory muscle use	Usually afebrile or low-grade
Auscultation	Clear, or transient rhonchi that clear with cough — no localized findings	Localized crackles, bronchial breath sounds, dullness to percussion	Diffuse wheeze, prolonged expiration	Usually clear between paroxysms
Cough pattern	Productive or dry, gradually improving, median 18 days, up to 8 weeks	Productive, associated with systemic illness	Associated with dyspnea and wheeze, not isolated	Paroxysmal, staccato coughing fits, inspiratory "whoop," post-tussive vomiting; can last 6-10 weeks
Key history clue	Preceding upper respiratory symptoms; no risk factors for pneumonia	Rigors, pleuritic chest pain, more unwell than expected for "a cold"	Known asthma/COPD, trigger exposure, prior exacerbations	Known outbreak or exposure, incomplete immunization, symptoms >2 weeks with paroxysms
Confirms/next step	Clinical diagnosis; no imaging or culture needed if vitals and exam are reassuring	Chest x-ray if suspected on history/exam	Peak flow/spirometry if available; treat per the relevant asthma/COPD pathway	PCR or culture from nasopharyngeal swab; notify public health
1st-line management	Supportive care only; antibiotics not recommended	Antibiotics per the Community-Acquired Pneumonia pathway	Bronchodilator/controller escalation per the relevant asthma/COPD pathway	Macrolide antibiotic (reduces transmissibility, may not shorten symptoms if started late) plus public health notification and contact prophylaxis

A normal heart rate (<100/min), normal respiratory rate (<24/min in adults), oral temperature <38°C, and absence of localized chest findings together have a negative predictive value of 96-100% for pneumonia in adults — when all four are present, chest x-ray is not needed.

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.

Treatment Targets

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

Choose Initial Treatment

Direct treatment rule

1st line supportive, symptomatic care only — patient education, hydration, humidity, and over-the-counter symptom relief as needed.

Routine antibiotics are not recommended, even when a bacterial cause is suspected in an otherwise healthy, clinically stable patient with no signs of pneumonia.^[4] A Cochrane review of 17 trials in almost 5,100 patients found antibiotics reduce cough duration by at most half a day, a benefit offset by adverse effects and antibiotic resistance (number needed to harm = 24).^[4]

Move to a different pathway — not "second-line acute bronchitis therapy" — the moment pneumonia, an asthma/COPD exacerbation, or pertussis is suspected; treat those conditions on their own pathway rather than escalating acute bronchitis treatment.

Non-Pharmacologic Treatment

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.

Pharmacologic Treatment Options

Drug / intervention	Role	Dose / use	Important adverse effects	Teaching points
Acetaminophen Preferred	Fever, headache, myalgia, chest discomfort	Adults/children >12y: 325-650 mg PO Q4-6H PRN, max 4 g/day. Children: 10-15 mg/kg PO Q4-6H PRN, max 5 doses/day or 75 mg/kg/day or adult dose, whichever is less	Well tolerated; rare GI upset; severe hepatotoxicity with overdose	Use with caution in hepatic impairment. In children, use only for fever.
Ibuprofen Preferred	Fever, headache, myalgia, chest discomfort (has not been shown to reduce cough severity/duration itself)	Adults: 200-400 mg PO TID-QID PRN, max 2.4 g/day. Children: 5-10 mg/kg PO Q6-8H PRN, max 40 mg/kg/day or adult dose, whichever is less	GI upset, epigastric pain, heartburn; possible increased blood pressure or GI bleed	Avoid in active peptic ulcer disease, IBD, ASA/NSAID intolerance. In children, use only for fever.
Dextromethorphan Alternative	Cough suppression	Adults/children >12y: 30 mg PO Q6-8H PRN, max 120 mg/day. Children 6-12y: 15 mg PO Q6-8H, max 60 mg/day	Rare nausea, drowsiness, dizziness	Not recommended in asthma or children under 6 years. Avoid with or within 2 weeks of an MAOI.
Codeine Special situation	Cough suppression when nonopioid options are inadequate	Adults: 10-20 mg PO Q4-6H PRN, max 120 mg/day	Sedation, nausea/vomiting, constipation	Not for use under 18 years of age (Health Canada). Avoid in breastfeeding. Weak evidence for benefit specifically in acute bronchitis.
Salbutamol Special situation	Only if wheeze, bronchial hyper-responsiveness, or FEV1 under 80% predicted	MDI: 1-2 puffs (100-200 mcg) QID PRN, max 800 mcg/day (400 mcg/day if under 12y)	Tremor, restlessness, palpitations, tachycardia	Not recommended for routine use in acute bronchitis — no benefit without airflow obstruction, and causes adverse effects (NNH=2).
Honey Preferred	Cough frequency/severity, adjunct	1-2 teaspoons as needed	None known when pasteurized	Pasteurized honey only, in immunocompetent children over 1 year — risk of infant botulism below that age.

Special Populations

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.

Monitoring & Follow-Up

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.

Treatment Failure / Next Step

Reassess for a missed diagnosis — pneumonia, asthma/COPD exacerbation, or pertussis — rather than assuming this is simply a slow-resolving acute bronchitis.
For cough persisting beyond 3 weeks, actively reconsider the differential; for cough beyond 8 weeks, transition to the Chronic Cough in Adults pathway.
For frequent or recurrent bouts of "bronchitis," evaluate for underlying asthma, COPD, bronchiectasis, GERD, or a medication cause (e.g., ACE-inhibitor-induced cough).
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.

Common Errors to Avoid

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.

Clinical Decision Algorithm

Management of suspected acute bronchitis

Patient presents with acute cough (under 3 weeks)

History and physical exam: vital signs, auscultation, exposure/vaccination history

Fever >38°C, HR >100/min, or localized chest findings

Reassess for pneumonia — obtain chest x-ray, manage per Community-Acquired Pneumonia if confirmed

Stridor, respiratory distress, or hypoxemia

Consider foreign body aspiration, epiglottitis, croup, or severe asthma/COPD exacerbation — urgent reassessment

Paroxysmal cough, whoop, post-tussive vomiting, or known pertussis exposure

Test for pertussis (PCR/culture), notify public health, treat with a macrolide and arrange contact prophylaxis

None of the above — reassuring vitals and exam

Diagnose acute bronchitis clinically — no imaging or culture needed

Educate: viral in >90% of cases, expected duration 2-3 weeks (up to 8), antibiotics not recommended

Supportive care: hydration, humidity, honey (if >1y), analgesics/antipyretics PRN, cough suppressant if sleep-disrupting

Wheeze, bronchial hyper-responsiveness, or FEV1 under 80% predicted

Consider a short-acting beta2-agonist trial

No airflow obstruction

No bronchodilator — no evidence of benefit

No improvement by 3 weeks, or any new red flag: reassess diagnosis rather than escalate acute bronchitis treatment

Drug Tables

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.

No pharmacologic treatment is required for most patients. The drugs below are for symptomatic relief only — none of them shorten the underlying illness, and none should be framed to the patient as "treating" the bronchitis.

Analgesics/antipyretics

For fever, headache, myalgia, or chest discomfort.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Acetaminophen	Adults and children >12y: 325-650 mg PO Q4-6H PRN, maximum 4 g/day Children: 10-15 mg/kg PO Q4-6H PRN, maximum 5 doses/day or 75 mg/kg/day or adult dose, whichever is less	Well tolerated; rare GI upset	May enhance warfarin's anticoagulant effect, particularly with doses >1.3 g/day for >1 week	Use with caution in hepatic impairment. Severe hepatic damage can occur with overdose.
Ibuprofen	Adults: 200-400 mg PO TID-QID PRN, maximum 2.4 g/day Children: 5-10 mg/kg PO Q6-8H PRN, maximum 40 mg/kg/day or adult dose, whichever is less	Primarily GI (nausea, epigastric pain, heartburn); possible increased blood pressure or GI bleed	ASA/anticoagulants may increase bleeding risk	Contraindicated in active peptic ulcer disease, IBD, or ASA/NSAID intolerance (asthma, anaphylaxis, urticaria, angioedema, rhinitis). Caution with reduced renal function, diuretics, ACE inhibitors, cardiac risk factors, or uncontrolled blood pressure. In children, use only in the presence of fever.

Antitussives

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

Drug	Dosage	Adverse effects	Drug interactions	Comments
Dextromethorphan	Adults and children >12y: 30 mg PO Q6-8H PRN, maximum 120 mg/day Children 6-12y: 15 mg PO Q6-8H, maximum 60 mg/day	Rare nausea, drowsiness, dizziness	Caution with other CNS depressants; do not use with or within 2 weeks of stopping an MAOI; SSRIs may enhance adverse effects	Not recommended in asthma or in children under 6 years.
Codeine	Adults: 10-20 mg PO Q4-6H PRN, maximum 120 mg/day	Sedation, nausea/vomiting, constipation	Additive sedation with other CNS depressants; CYP2D6 inhibitors (amiodarone, cimetidine, fluoxetine, moclobemide, paroxetine, quinidine) may reduce effect	Not for use under 18 years of age per Health Canada. Avoid in breastfeeding because of infant toxicity risk. Genetic variation in CYP2D6 metabolism can cause unpredictable effect or toxicity. Weak evidence for benefit specifically in acute bronchitis.
Hydrocodone	Adults: 5 mg PO Q4-6H PRN, may increase to 10 mg/dose, maximum 30 mg/day	Lightheadedness, dizziness, sedation, nausea/vomiting, constipation	Additive sedation and respiratory depression risk with other CNS depressants	Not for use under 18 years of age per Health Canada. Avoid in breastfeeding because of infant toxicity risk.

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.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Salbutamol	MDI, adults and children ≥4y: 1-2 puffs (100-200 mcg) QID PRN, maximum 800 mcg/day (adults/≥12y) or 400 mcg/day (under 12y) Diskus, adults and children ≥4y: 1 inhalation (200 mcg) TID-QID PRN, maximum 800 mcg/day	Tremor, restlessness, palpitations, dizziness, headache, nausea, hypokalemia, tachycardia	Caution with other sympathomimetic agents	Contraindicated in arrhythmias or hypertrophic obstructive cardiomyopathy. Caution with ischemic heart disease, vascular disease, hypertension.
Terbutaline	Adults and children ≥6y: 1 inhalation (0.5 mg) QID PRN, maximum 6 inhalations/day	Tremor, restlessness, palpitations, dizziness, headache, nausea, hypokalemia, tachycardia	Caution with other sympathomimetic agents	Contraindicated in arrhythmias or hypertrophic obstructive cardiomyopathy. Caution with ischemic heart disease, vascular disease, hypertension.

Natural health products

Modest evidence base; discuss expectations honestly with the patient.

Drug	Dosage	Adverse effects	Drug interactions	Comments
Honey	Adults and children >1y: 1-2 teaspoons as needed	None known when pasteurized	None known	Use pasteurized honey only, and only in immunocompetent children over 1 year of age — risk of infant botulism below that age. More effective than diphenhydramine, salbutamol, and placebo for cough frequency/severity; not shown to be better than dextromethorphan.

References

Acute cough due to acute bronchitis in immunocompetent adult outpatients: CHEST Expert Panel report — CHEST (Smith MP, Lown M, Singh S, et al.). Chest 2020;157(5):1256-1265
Appropriate antibiotic use for acute respiratory tract infection in adults: advice for high-value care from the American College of Physicians and the Centers for Disease Control and Prevention — Annals of Internal Medicine (Harris AM, Hicks LA, Qaseem A, et al.). Ann Intern Med 2016;164(6):425-434
How long does a cough last? Comparing patients' expectations with data from a systematic review of the literature — Annals of Family Medicine (Ebell MH, Lundgren J, Youngpairoj S). Ann Fam Med 2013;11(1):5-13
Antibiotics for acute bronchitis — Cochrane Database of Systematic Reviews (Smith SM, Fahey T, Smucny J, Becker LA). Cochrane Database Syst Rev 2017;6(6):CD000245
Honey for acute cough in children — Cochrane Database of Systematic Reviews (Oduwole O, Udoh EE, Oyo-Ita A, Meremikwu MM). Cochrane Database Syst Rev 2018;(4):CD007094
Health Canada recommends that children and youth not use cough and cold products that contain opioids — Health Canada. Recall/alert, February 18, 2019
Beta2-agonists for acute cough or a clinical diagnosis of acute bronchitis — Cochrane Database of Systematic Reviews (Becker LA, Hom J, Villasis-Keever M, van der Wouden JC). Cochrane Database Syst Rev 2015;(9):CD001726

Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.