Canonical Question
Resp Pharm – Asthma
Master answer
Asthma:
- Airway obstruction that is reversible (completely or partially) either spontaneously or with treatment,
- Airway inflammation (oedema and hypersecretion)
- Increased airway responsiveness to a variety of stimuli
General Measures:
- Oxygen.
- Repeated assessment
- ABGs
Specific Pharmacology:
| Class | Example | MoA |
|---|---|---|
| Adrenergic Agonists | Salbutamol Adrenaline | Predominantly acting at the β2-adrenergic receptor Gs-PRC → ↑AC → ↑cAMP → ↑PLC activity – ↓ [Ca] via ↑ uptake and removal from cytoplasm – Active uncoupling of actin-myosin via i) Phosphorylation of MLCK ii) Phosphorylation of MLCK Phosphatase – ↑ K channel activation → hyperpolarisation → SMC relaxation Mast cell stabilisation (adrenaline) Improved mucocillary function. |
| Methyxanthines (PDE3 inhibitors) | Theophylline Aminophylline | Multiple Actions ↓ PDE acitons → ↑ cAMP in bronchial SM → sim to β2 effect Adenosine receptor antagonism → ↓ adensosine related bronchoconstriction |
| Antimuscarinics | Tiotropium, Ipratropium | M3 receptor antagonists Normally ACh stimulates M3 → Gq-PRC → ↑ DAG/IP3 → ↑ bronchiolar tone Antagonism → ↓ Vagally mediated Decreased Gq mediated effects |
| Steroids | Prednisone, Hydrocortisone | Reverse the activating effect of pro-inflammatory transcription factors → decrease inflammation – Inhibit the formation of cytokines secreted in asthma by T-lymphocytes, macrophages, and mast cells – Decreased vascular permeability – Inhibitory effect on mucus glycoprotein secretion – ? enhance B2 effects. |
| Other | Mag Sulphate | Acts as a bronchodilator by decreasing cytosolic Ca2+ concentrations. |
| Heliox | Decreased density – thus increased air flow via Hagan Pouiselle | |
| Ketamine | Bronchial smooth muscle relaxant by inhibiting Ach mediated SM constriction | |
| Sevoflurane | Direct beta agonism and inhibition of histamine release from mast cells. |
Gladwin 2016
Exam appearances
| Exam | Exact wording | Relationship | Success |
|---|---|---|---|
| 2007B Q23 | Describe the mechanisms of action of drug groups commonly used to treat acute severe asthma. | historical_member | — |
| 2014B Q11 | Describe the mechanisms of action of drugs used to treat acute severe asthma and give examples. | historical_member | — |
| 2019B Q08 | Outline the pharmacology of drugs used to treat asthma. | historical_member | — |
| 2010A Q09 | Describe the mechanism of action of drugs commonly used to treat acute severe asthma. | historical_member | — |
| 2016B Q04 | Describe the mechanisms of action of drugs used to treat acute severe asthma and give examples. | historical_member | — |