Pharmacology
Gastrointestinal drugs
Gastrointestinal medicines are grouped by the process they change: acid secretion, transit through the gut, the vomiting reflex, or mucosal inflammation. Symptoms overlap heavily across these mechanisms, which is why the mechanism rather than the complaint organises the section.
7 classes across 3 mechanism families.
1. Acid-suppressing agents
These medicines reduce gastric acid secretion or neutralise acid already secreted, and differ principally in the speed and completeness of that effect.
- Proton pump inhibitors — Irreversible inhibitors of the gastric proton pump; long-term use carries its own risks.
- H2-receptor antagonists — Reversible histamine H2 blockers; a class reshaped by the withdrawal of ranitidine.
- Antacids and alginates — Neutralise or raft over gastric acid; interactions arise chiefly through altered absorption. (in preparation)
2. Gut motility and antiemetic agents
These medicines alter gastrointestinal transit or interrupt the receptors that drive nausea and vomiting, and are chosen by the mechanism of the symptom rather than by its severity.
- Laxatives and antidiarrhoeals — Agents that speed or slow transit, grouped by osmotic, stimulant, bulking or antimotility action. (in preparation)
- Antiemetics — Chosen by the receptor driving the nausea: dopaminergic, serotonergic, histaminergic or NK1. (in preparation)
- Antispasmodics — Reduce intestinal smooth muscle spasm, principally in irritable bowel syndrome. (in preparation)
3. Intestinal anti-inflammatory agents
These medicines suppress mucosal inflammation in inflammatory bowel disease, acting topically within the bowel or systemically on the immune response.
- Aminosalicylates and IBD agents — Topical mucosal anti-inflammatories central to ulcerative colitis maintenance. (in preparation)
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.