Preparatory Mindset
Asthma drugs are divided into RELIEVERS (short-acting bronchodilators for acute attacks) and PREVENTERS (anti-inflammatory controllers for long-term management). β2-agonists (salbutamol) are first-line relievers; inhaled corticosteroids are first-line preventers. Theophylline is narrow therapeutic index — monitor levels.
Core Concepts
Ch05: Respiratory
Key Drug Table — Antiasthmatic Drugs Classification
1. Bronchodilators
| Class | Drug(s) | MOA | Key Features |
|------|---------|-----|-------------|
| β2 Agonists (Short-acting / SABA) | Salbutamol | β2 receptor agonist → ↑ cAMP → bronchodilation | Most used and effective for acute asthma attacks; onset 5-15 min |
| β2 Agonists (Long-acting / LABA) | Salmeterol | β2 agonist (prolonged) | Maintenance therapy only; NOT for acute attack |
| Anticholinergics | Ipratropium | M-receptor antagonist → bronchodilation | Less effective than β2 agonists; adjunct for COPD |
| Theophylline | Aminophylline, Theophylline | PDE inhibitor → ↑ cAMP; also adenosine antagonist | Narrow therapeutic window; TDM required; many drug interactions |
2. Anti-inflammatory
| Class | Drug(s) | MOA | Key Features |
|------|---------|-----|-------------|
| Glucocorticoids (Inhaled) | Beclomethasone, Budesonide, Fluticasone | ↓ Inflammatory mediators | First-line controller therapy for persistent asthma |
| Glucocorticoids (Systemic) | Prednisone, Prednisolone | Same MOA | Acute severe exacerbations only; long-term → systemic side effects |
3. Anti-allergic / Prophylactic
| Class | Drug(s) | MOA | Key Features |
|------|---------|-----|-------------|
| Mast Cell Stabilizer | Sodium Cromoglycate | Stabilizes mast cells → ↓ histamine release | Prophylaxis only; no bronchodilation |
| Anti-allergic | Ketotifen | Mast cell stabilizer + H1 antagonist | Asthma prophylaxis + allergic conditions |
| Leukotriene Receptor Antagonist | Zafirlukast, Montelukast | Blocks CysLT1 receptors → ↓ leukotriene effects | Exercise-induced asthma prophylaxis; mild-moderate asthma |
Antitussive Drugs
| Drug | Type | Mechanism |
|------|------|-----------|
| Dextromethorphan | Non-opioid central antitussive | Suppresses medullary cough center; no addiction |
| Codeine | Opioid central antitussive | Suppresses cough center; risk of dependence |
| Benzonatate | Peripheral antitussive | Anesthetizes stretch receptors in respiratory tract |
Asthma Therapy Stepwise Approach
Step 1: SABA as needed
Step 2: Low-dose ICS (inhaled corticosteroid) + SABA as needed
Step 3: Low-dose ICS + LABA
Step 4: Medium-dose ICS + LABA
Step 5: High-dose ICS + LABA ± Oral steroid
Exam-Frequency Core Points (from exam notes)
1. H₁ Receptor Antagonists
| Drug Class | Representative Drugs | Core Exam Points | Frequency | 【Must-Know Details】 |
| --- | --- | --- | --- | --- |
| First-generation non‑selective H₁ receptor antagonists | Diphenhydramine, Promethazine | Clinical use: treatment of vomiting induced by motion sickness and radiation sickness | ★★★ | For motion sickness prevention, must be administered 30 minutes before travel/boarding to be effective; significant central sedative adverse effects; patients should not drive or operate precision machinery after taking |
| First-generation non‑selective H₁ receptor antagonists | Chlorpheniramine | Clinical use: anti‑allergic treatment for urticaria and allergic rhinitis | ★★ | Central sedative effects are weaker than those of diphenhydramine; commonly used as an anti‑allergic ingredient in combination cold remedies |
| Second-generation selective H₁ receptor antagonists | Loratadine | Mechanism: selectively blocks peripheral H₁ receptors with no significant central sedative effects; first‑line drug for allergic rhinitis, chronic urticaria, and various allergic dermatoses | ★★★ | Compared with first‑generation drugs, no somnolence side effects, does not affect daily work or study, no cardiotoxicity, and has a higher safety profile |
2. H₂ Receptor Antagonists
| Representative Drug | Core Exam Points | Frequency | 【Must-Know Details】 |
| --- | --- | --- | --- |
| Ranitidine | Mechanism: blocks H₂ receptors on gastric parietal cells to reduce gastric acid secretion; clinical use: commonly used for duodenal ulcer, also for gastroesophageal reflux disease and stress ulcers | ★★★ | Most potent inhibitor of basal gastric acid secretion; also clearly inhibits acid secretion induced by food, gastrin, and other stimuli |
II. Drugs Acting on the Respiratory System (core: asthma therapeutics, exam frequency: ~50%)
| Drug Class | Representative Drugs | Core Exam Points | Frequency | 【Must-Know Details】 |
| --- | --- | --- | --- | --- |
| Glucocorticoids | Inhaled budesonide, fluticasone, etc. | First‑line therapy for long‑term control of chronic asthma; administration route: inhalation | ★★★ | ❶ Absolutely contraindicated for rescue in status asthmaticus (inhaled administration has slow onset; status asthmaticus requires intravenous glucocorticoids); ❷ After long‑term inhalation, rinse mouth promptly to avoid local adverse effects such as oral candidiasis and hoarseness |
| Selective β₂‑adrenoceptor agonists | Terbutaline, Salbutamol | Mechanism: selectively stimulates β₂ receptors on airway smooth muscle, causing bronchodilation and relieving airway spasm | ★★★ | Short‑acting formulations are the first‑choice reliever medication for acute asthma exacerbations; use only as needed, not recommended for regular long‑term monotherapy (may lead to β₂ receptor down‑regulation and reduced efficacy) |
| Xanthines | Aminophylline | Mechanism: inhibits phosphodiesterase (PDE), increases intracellular cAMP and cGMP levels, relaxes bronchial smooth muscle; clinical use: treats both bronchial asthma and cardiac asthma | ★★★ | Very narrow therapeutic window; monitor plasma concentrations during therapy to avoid severe toxic reactions such as arrhythmias and convulsions |
| Mast cell stabilizers | Cromoglicate (Cromolyn sodium) | Clinical use: prophylactic treatment of asthma only | ★★★ | No direct bronchodilator effect; ineffective against ongoing asthma attacks; requires 7–10 days of pre‑treatment to achieve prophylactic effect; good preventive effect on exercise‑induced asthma and allergic asthma |
III. Drugs Acting on the Digestive System (core: acid‑suppressing agents, exam frequency: ~35%)
| Representative Drug | Core Exam Points | Frequency | 【Must-Know Details】 |
| --- | --- | --- | --- |
| Omeprazole (Proton Pump Inhibitor / PPI) | Mechanism: specifically inhibits the H⁺‑K⁺‑ATPase (proton pump) on gastric parietal cells, blocking gastric acid secretion at the final step; potent and long‑lasting acid suppression; also has anti‑Helicobacter pylori activity | ★★★ | ❶ Currently the most potent acid‑suppressing drug class; first‑choice treatment for gastric and duodenal ulcers, gastroesophageal reflux disease, and Zollinger‑Ellison syndrome; core component of the quadruple regimen for H. pylori eradication; ❷ Long‑term use requires vigilance for adverse effects such as osteoporosis and vitamin B₁₂ deficiency |
真题题目区
###
[ 【Respiratory System Drugs】](https://app.notion.com/p/Respiratory-System-Drugs-38af1f80e97c80c3b679f953860a5ae5?pvs=21)
[ 【Drugs Acting on the Digestive System】](https://app.notion.com/p/Drugs-Acting-on-the-Digestive-System-38af1f80e97c800b8589ed4ec24e4042?pvs=21)
High-Yield Points
- β2-agonists (salbutamol): RELIEVER — acute bronchodilation
- Inhaled corticosteroids (budesonide): PREVENTER — reduce inflammation
- Ipratropium: anticholinergic — alternative bronchodilator
- Theophylline: narrow therapeutic index (10-20 μg/mL)
- Leukotriene receptor antagonists (montelukast): oral, for mild-moderate asthma
- Status asthmaticus: systemic steroids + intensive bronchodilation
- Cromolyn: mast cell stabilizer — prophylaxis only
Topic Summary
Asthma management: β2-agonists (relievers) + inhaled corticosteroids (preventers). Leukotriene receptor antagonists are oral alternatives. Theophylline has narrow therapeutic window. Status asthmaticus requires systemic corticosteroids.