Pharmacology
Respiratory and Gastrointestinal Pharmacology
Respiratory and gastrointestinal drugs for MBBS and NEET-PG: bronchodilators, inhaled steroids, proton pump inhibitors and antiemetics, mapped to NMC codes.
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Respiratory and Gastrointestinal Pharmacology
Respiratory and gastrointestinal drugs for MBBS and NEET-PG: bronchodilators, inhaled steroids, proton pump inhibitors and antiemetics, mapped to NMC codes.
This chapter covers the drugs used in respiratory disease and gastrointestinal disorders. It includes bronchodilators and anti-inflammatory agents for asthma and chronic obstructive pulmonary disease, together with acid-suppressing drugs, antiemetics, antidiarrhoeals and laxatives.
High-yield: Respiratory and Gastrointestinal Pharmacology
- Inhaled short-acting beta-2 agonists such as salbutamol give rapid bronchodilatation and are the reliever of choice in acute asthma.
- Inhaled corticosteroids such as budesonide are the mainstay preventer therapy in persistent asthma, reducing airway inflammation.
- Ipratropium is an inhaled antimuscarinic useful in chronic obstructive pulmonary disease.
- Theophylline is a bronchodilator with a narrow therapeutic index causing arrhythmias and seizures at toxic levels.
- Montelukast, a leukotriene receptor antagonist, is useful in exercise-induced and aspirin-sensitive asthma.
- Proton pump inhibitors such as omeprazole irreversibly block the gastric proton pump and are the most potent acid suppressants.
- H2 receptor antagonists such as ranitidine reduce acid secretion but are weaker than proton pump inhibitors.
- Helicobacter pylori eradication uses a proton pump inhibitor with two antibiotics, typically clarithromycin and amoxicillin.
- Ondansetron, a 5-HT3 antagonist, is a potent antiemetic for chemotherapy and post-operative nausea.
- Metoclopramide is a prokinetic and antiemetic that can cause extrapyramidal side effects, especially in the young.
- Loperamide is an opioid antidiarrhoeal that acts locally on gut opioid receptors without central effects.
- Oral rehydration solution is the cornerstone of managing acute diarrhoea and dehydration.
- Bulk-forming and osmotic laxatives are preferred for chronic constipation; stimulant laxatives can cause cramping.
- Misoprostol, a prostaglandin analogue, protects the gastric mucosa against NSAID-induced ulcers but is abortifacient.
Airway and gut drug essentials
- **Asthma reliever:** Inhaled short-acting beta-2 agonist such as salbutamol.
- **Asthma preventer:** Inhaled corticosteroid such as budesonide reduces airway inflammation.
- **Acid suppression:** Proton pump inhibitors are the most potent; H2 blockers are weaker.
- **H. pylori eradication:** Proton pump inhibitor plus clarithromycin and amoxicillin.
NMC competencies in this chapter
- **PH1.32:** Drugs for bronchial asthma and cough
- **PH1.33:** Drugs for peptic ulcer and gastro-oesophageal reflux
- **PH1.34:** Antiemetics, drugs for constipation and diarrhoea
Frequently Asked Questions
What is the reliever versus preventer in asthma?
The reliever is an inhaled short-acting beta-2 agonist for acute symptoms, while the preventer is an inhaled corticosteroid taken regularly to control airway inflammation.
Why are proton pump inhibitors stronger than H2 blockers?
They irreversibly block the final common step of acid secretion, the proton pump, giving more complete and sustained acid suppression than H2 receptor antagonists.
How is Helicobacter pylori treated?
With triple therapy of a proton pump inhibitor plus two antibiotics such as clarithromycin and amoxicillin, given together for a set course.
Why can metoclopramide cause movement side effects?
It blocks dopamine receptors in the brain, which can produce extrapyramidal reactions such as dystonia, especially in children and young adults.
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