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PH5.1-2 | Respiratory Pharmacology — PBL Case
CLINICAL SETTING
Setting: Emergency Department, District Government Hospital, Palghar district, Maharashtra. Ramesh, a 38-year-old welder at a fabrication unit, arrives at the emergency department on a Tuesday evening with his wife, Sunita. He is visibly distressed — hunched forward, using his neck and shoulder muscles to breathe, unable to complete full sentences. His wife explains that he has been 'asthmatic since childhood' but had been managing well for years with 'a pump' (salbutamol MDI, which she produces from her bag). He started coughing heavily this morning after a particularly smoky shift and the 'pump stopped working' around noon. His breathlessness worsened through the afternoon. He also started a new tablet for his blood pressure two weeks ago, which a visiting doctor at his factory had prescribed. His wife cannot recall the name but produces the strip — enalapril 5 mg OD. Vitals: Temp 37.1°C, HR 118/min, RR 28/min, SpO2 88% on air, BP 138/82 mmHg. Auscultation: bilateral diffuse expiratory wheeze. Accessory muscle use noted. He is too breathless to speak a full sentence (speaking in 2-3 word fragments).
Trigger 1: Trigger 1 — Acute Presentation: Classifying Severity and Initiating Rescue
The emergency room nurse hands you the triage card: SpO2 88% on room air, HR 118/min, RR 28/min. Ramesh can say only 'cannot breathe' in Hindi. He is using sternocleidomastoid accessory muscles. His wife says his inhaler has been empty since noon — approximately 7 hours ago. Additional information now available: - Salbutamol MDI canister is shaken by the nurse — it makes no sound (empty) - No nebuliser mask is immediately available; you can access a nebuliser machine and vials of salbutamol (2.5 mg/2.5 mL) and ipratropium (0.5 mg/2 mL) - Oxygen is available via face mask - Intravenous access is being established
DISCUSSION POINTS
- Using standard guidelines (GINA), how would you classify the severity of this acute asthma exacerbation? List the parameters you used from the case.
- What is the immediate pharmacological management? For each drug you would use in the first 60 minutes, state: the drug, dose, route, mechanism of action, and rationale for use in acute severe asthma.
- Why is combining nebulised ipratropium with salbutamol more effective than salbutamol alone in the acute setting? Explain pharmacologically.
Click to reveal Trigger 2: Trigger 2 — The Drug History Problem and Stabilisation (discuss previous trigger first!)
Trigger 2: Trigger 2 — The Drug History Problem and Stabilisation
After 40 minutes of nebulised salbutamol (2.5 mg q20 min × 3 doses) + ipratropium (0.5 mg × 1 dose) + high-flow oxygen + IV hydrocortisone 100 mg, Ramesh's SpO2 improves to 95% and RR decreases to 20/min. He can now speak in short sentences. He reports: 'The blood pressure tablet the factory doctor gave me — since I started it two weeks ago I have a constant cough. Like a tickle that doesn't go away. I thought it was the smoke at work.' He also mentions: 'I have had asthma attacks before when I get flu, but never this bad from work smoke. The last two years my attacks have been happening more often — maybe 3-4 times per year, and I use the pump every day now.' Current inhalers: salbutamol MDI (just finished), no controller inhaler prescribed. His spirometry done last year at a private clinic: FEV1 68% predicted (available in a referral letter he carries).
DISCUSSION POINTS
- Identify and explain the drug-related problem in Ramesh's case. Name the mediator responsible, its source, and the specific receptor it activates to trigger cough.
- Based on his history (symptom frequency, SABA use pattern, FEV1, exacerbation rate), what GINA classification does Ramesh have as a baseline? What controller therapy should he have been on?
- Propose the complete ongoing management plan for Ramesh after discharge: include step-appropriate controller therapy with specific drugs, doses, devices, and a plan for the antihypertensive issue.
Click to reveal Trigger 3: Trigger 3 — Discharge Planning and Occupational Context (discuss previous trigger first!)
Trigger 3: Trigger 3 — Discharge Planning and Occupational Context
Ramesh is admitted for overnight observation. By the next morning, his SpO2 is 98% on room air, wheeze has resolved, and he is talking freely. He is given a discharge prescription by the admitting officer: salbutamol MDI PRN + oral prednisolone 40 mg OD x 5 days. Sunita asks two questions: 1. He works in a welding shop with metal fumes and smoke. Should he change his job? 2. The doctor in the ward said he needs a steroid inhaler permanently. He is afraid of steroids — he has seen his father (a diabetic) gain weight from steroid tablets. Will the inhaler also do that? You are the pharmacology-based consultant called to review the discharge prescription and counsel the family.
DISCUSSION POINTS
- Is the discharge prescription pharmacologically complete and appropriate? Identify any problems and rewrite the corrected prescription with full justification.
- How would you counsel Ramesh and Sunita regarding the safety of inhaled corticosteroids (ICS) compared to oral corticosteroids — covering systemic bioavailability, local adverse effects, and how to prevent them?
- The occupational trigger is persistent metal fume exposure. How does this relate to airway pharmacology — specifically, why might ongoing occupational exposure reduce the efficacy of controller therapy?
Group Task Assignments
Group 1: Acute pharmacotherapy mechanisms
- Prepare a tabulated summary comparing salbutamol (SABA), ipratropium (SAMA), and IV hydrocortisone: mechanism, onset, duration, and role in acute severe asthma.
- Explain why IV/IM corticosteroids are used in acute exacerbations despite their slower onset (~4-6 hours for full anti-inflammatory effect).
Competencies: PH5.1
Group 2: GINA step therapy for Ramesh's chronic asthma
- Apply GINA 2023 step therapy to Ramesh's chronic asthma history: determine correct step, and build a complete inhaler regimen with generic drug names, formulation, dose, and schedule.
- Explain the asthma-LABA safety rule: why is LABA + ICS safe when LABA alone is contraindicated?
Competencies: PH5.1
Group 3: ACE inhibitor cough — mechanism and management
- Prepare a short summary (3-4 paragraphs) explaining the mechanism of enalapril-induced cough: name the mediator, enzyme inhibited, receptor activated, and reflex arc involved.
- Propose the pharmacological management change for Ramesh's hypertension that resolves the cough issue — and justify why this drug class does not cause the same problem.
Competencies: PH5.2
Group 4: ICS safety profile and patient counselling
- Prepare a counselling script for Ramesh about his ICS: address his steroid fear by comparing the systemic bioavailability of inhaled ICS vs oral prednisolone using pharmacokinetic data.
- List the local adverse effects of ICS (oral candidiasis, dysphonia) with mechanism and prevention strategies.
Competencies: PH5.1
Group 5: Occupational asthma and pharmacological considerations
- Research the concept of occupational asthma triggers (metal fumes, isocyanates, welding smoke) and explain how repeated antigen exposure can cause airway sensitisation and beta-2 receptor downregulation.
- Propose a monitoring plan for Ramesh: what clinical and pharmacological parameters would indicate that his asthma is worsening despite controller therapy, and how would the regimen be stepped up?
Competencies: PH5.1
Learning Issues
Research these questions and bring your findings to the discussion.
- [PH5.1] What are the GINA 2023 criteria for classifying acute asthma exacerbation severity (mild, moderate, severe, life-threatening), and what is the step-by-step acute pharmacological management for each severity?
- [PH5.1] Compare the pharmacodynamics of the two major bronchodilator classes — beta-2 agonists and muscarinic antagonists — in terms of receptor, signalling cascade, cellular effect, onset, duration, and clinical indications in both asthma and COPD.
- [PH5.1] Explain the GINA step therapy for chronic asthma management. What is the pharmacological rationale for adding ICS before LABA? Why is LABA monotherapy contraindicated in asthma?
- [PH5.1] What are the pharmacokinetic differences between inhaled corticosteroids and oral corticosteroids that explain the superior local-to-systemic effect ratio of ICS? Include first-pass metabolism, bioavailability, and receptor binding affinity.
- [PH5.2] Explain the mechanism of ACE inhibitor-induced cough, identifying the specific mediator, its site of accumulation, the receptor activated, and the afferent nerve stimulated. Why does switching to an ARB resolve the cough?