PH5.1-2 | Respiratory Pharmacology — Glossary

The active metabolite of bromhexine with additional surfactant-stimulating properties; used as a mucolytic in productive cough and in neonatal respiratory distress syndrome prevention.

A drug that suppresses the cough reflex, acting either centrally at the medullary cough centre (e.g. codeine, dextromethorphan) or peripherally on vagal afferents (e.g. benzonatate); indicated only for dry (non-productive) cough.

A peripheral antitussive that acts as a local anaesthetic on vagal afferent stretch receptors (RARs) in the respiratory tract, suppressing the afferent limb of the cough reflex without CNS effects.

Monoclonal antibody targeting a specific mediator in severe asthma: omalizumab (anti-IgE), mepolizumab/reslizumab (anti-IL-5), benralizumab (anti-IL-5Rα), dupilumab (anti-IL-4Rα).

A synthetic mucolytic and mucokinetic agent derived from vasicine that stimulates serous secretion and reduces mucin production, lowering sputum viscosity; its active metabolite is ambroxol.

The neural pathway of the cough reflex: sensory afferents (vagal rapidly adapting receptors and C-fibres) → medullary cough centre (nucleus tractus solitarius integration) → motor efferents (respiratory muscles, glottic closure).

A hepatic cytochrome P450 enzyme responsible for metabolising codeine to its active form morphine; genetic polymorphisms produce ultra-rapid, extensive, intermediate, and poor metabolisers, with ultra-rapid metabolisers at risk of opioid toxicity from codeine.

Drug class (montelukast, zafirlukast) that blocks receptors for cysteinyl leukotrienes (LTC4/LTD4/LTE4) on bronchial smooth muscle; reduces asthma symptoms and approved for allergic rhinitis.

A soothing agent (e.g. honey, glycerol, simple linctus) that forms a coating over inflamed mucosa to relieve irritation; WHO-recommended first-line for cough in children aged 1–5 years.

A non-opioid central antitussive acting as an NMDA receptor antagonist and sigma-1 receptor agonist; not analgesic at therapeutic doses; absolutely contraindicated with MAOIs due to serotonin syndrome risk.

A drug that increases the volume or reduces the viscosity of bronchial secretions by stimulating reflex serous secretion, facilitating expectoration in productive cough (e.g. guaifenesin).

Global Initiative for Asthma framework for evidence-based, stepwise escalation (Steps 1–5) and de-escalation of asthma maintenance and reliever therapy based on symptom control and exacerbation risk.

Global Initiative for Chronic Obstructive Lung Disease classification dividing patients into Groups A, B, E based on symptom burden and exacerbation risk, guiding COPD pharmacotherapy selection.

The most widely used OTC expectorant; stimulates reflex bronchial secretion via a gastro-pulmonary vagal reflex, increasing secretion volume and reducing apparent mucus viscosity.

Anti-inflammatory agents that reduce eosinophilic airway inflammation; cornerstone of asthma maintenance from Step 2; added selectively in COPD with associated pneumonia risk.

Inhaled bronchodilator with duration ≥12 hours (e.g., salmeterol, formoterol); must always be combined with ICS in asthma due to a boxed warning for increased asthma-related deaths with monotherapy; acceptable as monotherapy in COPD.

Once-daily anticholinergic bronchodilator (prototype: tiotropium) blocking M3 receptors; the cornerstone long-acting bronchodilator class for COPD maintenance; add-on for severe asthma.

A peripheral antitussive with opioid-like action on C-fibre afferents; has no central opioid effects and is used when central antitussive adverse effects need to be avoided (elderly, alert-work requirements).

Maintenance and Reliever Therapy: uses low-dose ICS-formoterol as both daily controller and as-needed reliever in asthma (GINA Step 1–3); possible because formoterol has fast onset (3 min) unlike salmeterol.

A drug that directly reduces mucus viscosity either by cleaving disulfide bonds in mucin glycoproteins (e.g. NAC, carbocisteine) or by stimulating serous secretion and reducing goblet-cell mucin production (e.g. bromhexine, ambroxol).

A mucolytic that cleaves disulfide bonds in mucin glycoproteins to reduce sputum viscosity; also a glutathione precursor used at higher doses as the antidote for paracetamol (acetaminophen) overdose.

A cough that produces sputum from the lower respiratory tract, indicating excess mucus accumulation; a protective reflex for which antitussives are contraindicated.

Rebound nasal congestion occurring after prolonged use (>5 days) of topical decongestants (alpha-agonists), caused by receptor downregulation and reactive mucosal hyperaemia.

Selective PDE4 inhibitor approved as add-on oral therapy for severe COPD with chronic-bronchitis phenotype and frequent exacerbations; reduces exacerbation frequency but not for asthma or emphysema-only phenotype.

Inhaled bronchodilator with onset 3–5 min and duration 4–6 hours (e.g., salbutamol, terbutaline); used as rescue medication for acute bronchospasm in asthma and COPD.

A potentially life-threatening drug reaction caused by excess serotonergic activity, characterised by hyperthermia, agitation, neuromuscular excitability (clonus, hyperreflexia), and autonomic instability; relevant to dextromethorphan combined with MAOIs or SSRIs.

Methylxanthine bronchodilator and anti-inflammatory; narrow therapeutic index (5–15 µg/mL); CYP1A2 substrate with numerous drug and food interactions (smoking induction); requires therapeutic drug monitoring.

The concept that the upper (nasal) and lower (bronchial) airways constitute a continuous inflammatory unit; untreated rhinitis worsens asthma control through post-nasal drip, shared allergen sensitisation, and neurogenic reflex mechanisms.