Pharmacology
Respiratory and allergy drugs
Respiratory medicines separate cleanly into those that relieve airway narrowing within minutes and those that suppress the inflammation causing it over weeks. Confusing the two is the commonest clinical error in this area, so the grouping here follows that division.
6 classes across 3 mechanism families.
1. Antihistamines and allergy agents
These medicines block the histamine H1 receptor or otherwise interrupt allergic mediator release. Generation determines sedation far more than potency does.
- Antihistamines — H1 receptor antagonists; the first- and second-generation split is entirely about central nervous system penetration.
2. Bronchodilators
These medicines relax airway smooth muscle through beta-2 adrenoceptor stimulation, muscarinic blockade or phosphodiesterase inhibition, and are separated into reliever and maintenance roles.
- Beta-2 agonist bronchodilators — Short- and long-acting relievers and maintenance agents; tremor and hypokalaemia are class effects.
- Antimuscarinic bronchodilators — Block airway muscarinic receptors; central in COPD maintenance therapy.
- Methylxanthines — Theophylline and relatives; a narrow therapeutic index with major interaction potential.
3. Inhaled and anti-inflammatory airway agents
These medicines suppress airway inflammation rather than relieving bronchoconstriction, and act over days to weeks rather than minutes.
- Inhaled and intranasal corticosteroids — The maintenance backbone of asthma therapy; local and systemic effects follow dose and device technique.
- Leukotriene receptor antagonists — Oral anti-inflammatory agents carrying a neuropsychiatric safety warning.
Studying this the efficient way
Learn the mechanism family first, then the classes inside it. Almost every exam question about spectrum, adverse effects or resistance is really a question about which mechanism a drug belongs to. Each class page ends with a 60-second revision block and the traps students most often fall for.