Chemistry · Ch 15 — Chemistry in Everyday Life
Drug
Drug
A drug, at its simplest, is any substance used to modify or investigate a physiological system or a diseased state for the benefit of the person taking it -- for diagnosis, prevention, or the cure or relief of a disease. The English word traces back to the French drogue, "dry herb", a reminder that early medicines were literally dried plant material.
Not every drug is automatically a medicine in the strict sense: a drug earns that label only when it interacts with a macromolecular target -- typically a protein -- to produce a genuinely therapeutic, useful biological response. Using such a medicine to treat a specific disease is called chemotherapy. …
Therapeutic Action of Different Classes of Drugs
Deeper biological understanding of a disease mechanism translates directly into safer, better-targeted drugs -- and the unit uses stomach acidity to make the point concrete. Older treatments for acidity relied on weak bases such as aluminium and magnesium hydroxide, which simply neutralise the acid already present. That approach has two drawbacks: it can push the stomach alkaline enough to trigger a rebound surge in acid production, and it treats only the symptom, not the underlying cause. Once researchers established that histamine drives HCl secretion by activating a specific receptor on the stomach wall, drugs such as cimetidine and ranitidine were deliberately designed to resemble histamine's structure closely enough to occupy and disable that same receptor -- switching off excess acid production at its source rather than mopping it up afterward. …