Asthma in Adults and Adolescents

Asthma is a heterogeneous, chronic inflammatory disorder of the airways characterized by paroxysmal or persistent respiratory symptoms — dyspnea, chest tightness, wheeze, and cough, often with sputum production — together with variable expiratory airflow limitation and airway hyperresponsiveness.^[1] Airway inflammation, not bronchospasm alone, is the core pathophysiology: it drives both the acute, largely reversible airflow limitation typical of asthma and, if poorly controlled over time, progressive structural airway changes. Symptoms characteristically vary in frequency and intensity as inflammation and airflow limitation worsen or improve, often in relation to identifiable triggers such as allergens, exercise, viral infection, or irritant exposure.^[2]

The target for asthma control, used identically by GINA and the Canadian Thoracic Society, is daytime symptoms on 2 or fewer days per week and reliever use on 2 or fewer doses per week, with no nocturnal symptoms and no limitation of normal activity.^[1][2] This chapter covers the diagnosis and stepwise pharmacologic and non-pharmacologic management of asthma in adults and adolescents (12 years of age and older), following the current GINA/Canadian Thoracic Society treatment-track framework for this age group; asthma management in younger children uses a different treatment continuum and dosing structure and is addressed separately.

Typical presentation

Episodic or persistent dyspnea, chest tightness, wheeze, and cough, frequently worse at night or in the early morning, and precipitated or worsened by exercise, cold air, allergen exposure, viral upper respiratory infection, or irritant exposure. Symptoms are characteristically variable — better on some days than others — and often cluster into a recognizable trigger-related pattern (seasonal, occupational, exercise-induced, perennial).^[1]

Atypical or subtle presentation

Cough may be the only or predominant symptom (cough-variant asthma), particularly at night. Some patients report only chest tightness or a sensation of breathlessness without overt wheeze. A history of gradually reducing activity to avoid triggering symptoms is itself a clue to poorly controlled disease that patients often do not volunteer unprompted.

Examination findings

Wheeze on auscultation — which may be absent between exacerbations, and in a severe exacerbation with minimal air movement a "silent chest" is a red flag, not reassurance — nasal polyps, nasal congestion consistent with comorbid allergic rhinitis, and voice changes. The absence of crackles, unilateral wheeze, or digital clubbing helps distinguish asthma from alternative diagnoses such as bronchiectasis, a unilateral airway lesion, or interstitial lung disease.^[2]

• Family history of asthma or atopic disease (eczema, allergic rhinitis).
• Personal history of atopy, allergic rhinitis, or eczema.
• Environmental allergen exposure (house dust mite, pet dander, mould, seasonal pollen).
• Occupational exposures and irritants — an important and under-recognized cause of new-onset asthma in adults; take a thorough occupational history in any adult presenting with new asthma symptoms.
• Active or second-hand exposure to tobacco smoke, vaping, or cannabis smoke.
• Viral respiratory infections.
• Obesity.
• Chronic rhinitis or rhinosinusitis.
• Gastroesophageal reflux disease.
• Anxiety and depression.
• ASA or NSAID sensitivity, particularly in patients with nasal polyps or chronic rhinosinusitis (ASA-exacerbated respiratory disease).
• Non-selective beta-blocker exposure, including ophthalmic formulations, which can precipitate bronchospasm.
• Sulfite-containing food or drug preservatives.

Distinguishing asthma from its most important mimic: COPD

Asthma-COPD overlap exists when a patient has features of both, particularly older patients with a long-standing asthma history who also smoke — see Special Populations below.

History

• Family history of asthma and atopy.
• Symptom frequency, severity, and timing, including nighttime versus daytime pattern.
• Pattern of symptoms — seasonal, perennial, diurnal variation.
• Precipitating factors — environmental allergens, occupational exposures, irritant smoke, ASA/beta-blocker exposure, sulfite preservatives, viral respiratory infections, exercise, rhinitis, sinusitis, gastroesophageal reflux, obesity, anxiety, depression.
• Previous oral corticosteroid courses, emergency department visits, and any intensive-care admissions for asthma.

Objective testing

• Spirometry is the preferred method of diagnosis — reduced expiratory flow rates with reversibility (an increase in FEV1 of at least 12% and at least 200 mL after a bronchodilator, or after a therapeutic trial of controller therapy, supports the diagnosis in adults).^[2]
• Home peak flow monitoring — useful to help diagnose asthma when spirometry is unavailable, and to monitor patients with severe asthma or poor perception of airway obstruction.
• Bronchoprovocation challenge testing (methacholine or histamine) in a lung function laboratory when the diagnosis remains in doubt after spirometry.
• Biomarkers to guide treatment response and biologic eligibility in moderate-to-severe asthma — blood eosinophil count, fractional exhaled nitric oxide (FeNO), and serum IgE; these are not required for routine diagnosis of straightforward asthma.

When not to test: normal spirometry performed between symptomatic episodes does not exclude asthma — repeat testing when symptomatic, or proceed to bronchoprovocation challenge, rather than concluding the diagnosis is excluded from a single normal result.

Assessing asthma control at every visit

Control should be assessed at every clinical encounter using the following criteria; a patient meeting all of them is considered well controlled.^[2]

Risk factors for a severe exacerbation

Assessed separately from current symptom control, since a patient can be well controlled on therapy but still be at elevated exacerbation risk:

• Any history of a previous severe exacerbation (requiring systemic steroids, an emergency department visit, or hospitalization) — the single strongest predictor of a future severe exacerbation.
• Currently poorly controlled asthma.
• Overuse of a SABA reliever (more than 2 inhalers of roughly 200 doses each per year).
• Current smoking.
• Reduced FEV1.
• Comorbid atopic/allergic disease.

• Prevent asthma-related mortality.
• Prevent exacerbations.
• Daytime symptoms on 2 or fewer days per week.
• No nocturnal symptoms or night waking due to asthma.
• Maintain normal activity levels, including the ability to exercise without limitation.
• Need for reliever therapy on 2 or fewer occasions per week.
• Normal or near-normal lung function.
• Minimize medication adverse effects by using the lowest treatment step that maintains control.
• Minimize or avoid maintenance oral corticosteroid exposure.

• Identify and avoid precipitating factors — environmental allergens and occupational irritants specific to the patient.
• Smoking and vaping cessation (including cannabis and substances other than tobacco) is essential; also advise avoidance of second-hand smoke exposure.
• Treat modifiable comorbidities that worsen asthma control — obesity (nutrition, weight loss, regular physical activity), chronic rhinosinusitis, gastroesophageal reflux disease, obstructive sleep apnea, anxiety, and depression.
• Allergen immunotherapy (subcutaneous or sublingual) can be considered as an adjunct to standard pharmacotherapy when there is clear evidence linking allergen exposure to persistent, suboptimally controlled symptoms. Do not initiate in a patient with poorly controlled asthma — severe, possibly fatal reactions are more frequent in this population. Do not use house dust mite sublingual immunotherapy if FEV1 is 70% predicted or less.^[1]
• Home air cleaners/purifiers are not independently supported by evidence, although HEPA filtration may reduce some allergen levels as part of a broader environmental-control strategy.
• Inhaler technique should be reviewed and observed at every encounter. Do not prescribe two different device types (for example a pMDI and a DPI) to the same patient, since this increases technique errors.
• Provide every patient with a written asthma action plan describing daily preventive therapy, how to adjust reliever (and, for patients prone to exacerbations, controller) therapy for worsening symptoms, and when to seek urgent medical attention.
• Annual influenza vaccination is recommended for all patients with asthma without contraindication; the live-attenuated influenza vaccine is contraindicated in patients who are pregnant or who have severe asthma (current oral or high-dose inhaled corticosteroid use, or active or recently medically-attended wheeze).
• Pneumococcal vaccination is recommended for patients with a history of an asthma exacerbation requiring medical care in the past year, per current national immunization guidance.
• Encourage patients with asthma to stay up to date with all age- and risk-appropriate vaccinations, including COVID-19 (with booster doses as recommended) and RSV vaccination for adults 60 years of age and older.
• Bronchial thermoplasty — an endoscopic procedure using radiofrequency pulses to reduce airway smooth muscle — remains an experimental therapy available only at a small number of specialized centres, considered for severe asthma uncontrolled by persistent bronchial hyperreactivity when biologic therapy is not suitable, not effective, or not tolerated.

Pregnancy

Pregnancy does not affect asthma in a predictable direction — some patients worsen, some improve, and some see no change, and the pattern tends to persist across subsequent pregnancies. What matters far more than the medications themselves is control: poorly controlled asthma in pregnancy is associated with preterm birth, low birth weight, pre-eclampsia, and placenta previa, while good control is associated with normal outcomes. Manage asthma in pregnancy using the same stepwise approach as in non-pregnant patients — do not under-treat out of medication-safety concerns.^[1]

SABAs and inhaled corticosteroids (particularly budesonide, which has the most extensive pregnancy safety data of any ICS) have been used extensively in pregnancy and are considered safe. Montelukast and LABAs (used with an ICS, never alone) have not shown adverse pregnancy effects in accumulating experience. Theophylline is considered safe but is rarely used given its narrow therapeutic index and lower efficacy. Data on biologic therapies in pregnancy remain limited; the risk of continuing or withholding biologic therapy must be individually weighed against the risk of uncontrolled severe asthma to the pregnancy.

Breastfeeding

Breastfeeding has no known effect on asthma severity. Bronchodilators (SABA, LABA, muscarinic antagonists) and both inhaled and oral corticosteroids are considered safe during breastfeeding. Montelukast is transferred into breast milk but is itself approved from 6 months of age. Data on biologic therapy during breastfeeding remain limited, and the established benefits of breastfeeding should be weighed against any theoretical risk.

Adolescents

Asthma control is often reduced in adolescents, and poor adherence to treatment is a major contributor. Contributing factors include: newly assumed responsibility for self-managing therapy, forgetfulness or being too busy to use an inhaler, social stigma around inhaler use, introduction of alcohol, cannabis, or tobacco use, emerging mental health comorbidities, and financial burden. Improve adherence in this group by regularly reviewing inhaler technique, matching device selection to patient preference and ease of use, considering a switch from SABA-based therapy to ICS-formoterol (Track 1), counselling on the respiratory risks of smoking and cannabis, and screening for comorbid mental health conditions.

Older adults

No specific dose adjustment is required for inhaled therapy based on age alone. Consider bone density and cataract/glaucoma risk when higher-dose ICS is needed long-term, and be alert to reduced inspiratory flow limiting dry powder inhaler effectiveness in frail patients.

Comorbid asthma and COPD

Patients with features of both asthma and COPD (asthma-COPD overlap) should receive sufficient ICS to control airway inflammation together with sufficient bronchodilator therapy to manage symptoms; therapy is individualized based on lung function, exacerbation history, symptoms, and eosinophil levels, and combination ICS/LABA ± LAMA therapy is often required.

Renal and hepatic impairment

Inhaled therapy has minimal systemic absorption and generally requires no renal or hepatic dose adjustment. Strong CYP3A4 inhibitors can meaningfully increase systemic exposure to several inhaled corticosteroids (see Drug Tables). No clinically important renal or hepatic dose adjustment has been established for the biologic agents based on current product information.

Review symptom control and risk factors for exacerbation (see Assessment & Diagnosis) at every visit, and formally every 3-6 months once therapy is established. Review inhaler technique at every encounter — technique errors are common and directly associated with worse control. Repeat spirometry periodically to track lung function trajectory, and monitor growth velocity in adolescents on medium-to-high-dose ICS long-term. Consider bone density assessment in patients on long-term high-dose ICS or repeated oral corticosteroid courses. Check adherence at every visit, including refill patterns beyond the first fill, since non-adherence is a leading and correctable cause of apparent poor control. Confirm the written asthma action plan is current and that the patient understands when to step up self-management versus seek urgent care. Reassess vaccination status annually.

1. Confirm the diagnosis is correct — reconsider alternative or coexisting diagnoses (vocal cord dysfunction, cardiac disease, bronchiectasis, uncontrolled rhinitis/GERD) before assuming this is simply undertreated asthma.
2. Check inhaler technique and adherence, including refill patterns, before escalating therapy — a large proportion of apparent treatment failure is technique or adherence failure, not true refractory disease.
3. Address contributing comorbidities (obesity, GERD, rhinosinusitis, anxiety/depression) and ongoing trigger or occupational exposure.
4. For self-managed worsening within a written action plan ("yellow zone"): on Track 1 (bud/form), increase to a maximum of 8 inhalations/day (or, in patients 16 years of age and older with a severe exacerbation in the past year, increase to up to 4 inhalations twice daily for 7-14 days); on Track 2 with a history of a severe exacerbation in the past year, a trial of a 4-fold or greater increase in maintenance ICS dose for 7-14 days is the 1st choice, with prednisone 30-50 mg once daily for at least 5 days as the 2nd choice. Seek urgent medical attention if there is no sustained improvement.^[2]
5. Step up within the current track, or switch tracks, per the algorithm — only after confirming steps 2-3 above.
6. If uncontrolled despite confirmed adherence on medium-to-high-dose ICS-LABA (± LAMA), obtain blood eosinophils, FeNO, and serum IgE, and refer for phenotype-guided biologic therapy.^[3]
7. Refer to a specialist for diagnostic uncertainty, suspected occupational asthma, or any history of a near-fatal exacerbation.

• Continuing SABA monotherapy in a patient with any risk factor for exacerbation.
• Prescribing budesonide/formoterol as a reliever alongside a different, non-formoterol-containing ICS-LABA product — only budesonide/formoterol is approved for reliever/MART use.
• LABA monotherapy without a concurrent inhaled corticosteroid.
• Doubling the ICS dose empirically for worsening symptoms — evidence supports only a 4-fold-or-greater increase, and only in specific higher-risk patients with a history of severe exacerbation, not routine dose-doubling.
• Completely stopping ICS once control is achieved — always step down gradually, never stop entirely.
• Prescribing two different inhaler device types to the same patient, which increases technique errors.
• Not reviewing inhaler technique at every visit.
• Missing an occupational asthma workup in new adult-onset disease.
• Uncautious ASA/NSAID use in a patient with nasal polyps, chronic rhinosinusitis, or known ASA-exacerbated respiratory disease.
• Uncautious beta-blocker use, including ophthalmic formulations, which can precipitate bronchospasm.
• Empiric antibiotics for an asthma exacerbation without evidence of bacterial infection.
• IV aminophylline in the first hours of an acute severe exacerbation.
• Targeting 100% oxygen saturation instead of the recommended 93-95% target during an exacerbation.
• Delaying systemic corticosteroids beyond the first hour of presentation for a moderate-to-severe exacerbation.
• Missing biologic-eligible severe asthma by not checking blood eosinophils, FeNO, or IgE in a patient uncontrolled on high-dose ICS-LABA.

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.

Short-acting beta2-agonists (SABAs)

Short-acting muscarinic antagonist (SAMA)

SAMA/SABA combination (acute exacerbations only)

Long-acting beta2-agonists (LABAs) — never as monotherapy

Health Canada carries a boxed warning against LABA monotherapy in asthma; always pair with an inhaled corticosteroid.

Inhaled corticosteroids (ICS), single agent — dosing categories by potency

Low/medium/high categories are Canadian-approved adult dosing tiers.

ICS-formoterol (Track 1 anti-inflammatory reliever and MART)

The only ICS-LABA combination approved in Canada for reliever use; the same inhaler is used across every Track 1 step.

ICS-LABA (Track 2 maintenance only — not for reliever use)

Long-acting muscarinic antagonist (LAMA) add-on

Triple therapy (ICS/LABA/LAMA)

Indicated when asthma remains uncontrolled on ICS-LABA alone.

Leukotriene receptor antagonist

Methylxanthines

Uncommon in current North American practice given a narrow therapeutic index and multiple drug interactions.

Systemic corticosteroids

Biologics — Anti-IgE

Initiate only with significant expertise in asthma management, and administer under supervision of a professional experienced in managing anaphylaxis.

Biologics — Anti-interleukin-5 / anti-IL-5 receptor

Biologics — Anti-interleukin-4 receptor alpha

Biologics — Anti-thymic stromal lymphopoietin (anti-TSLP)