Drugs in Medicine

What is a Drug?

The Definition

A drug is any substance taken into the body that modifies or affects chemical reactions in the body.

Types of Drugs

Not all drugs are the same. We classify them into different groups based on what they do:

• Medicinal drugs: Used to treat symptoms or cure diseases. Examples: antibiotics, painkillers, vaccines.
• Recreational drugs: Taken for pleasure (not our focus here).
• Addictive drugs: Cause dependence on repeated use.

Where are drugs processed?

The liver is the primary site where drugs are broken down and metabolised in your body. This process is crucial because it:

• Converts drugs into forms your body can eliminate (usually through urine)
• Determines how long a drug stays active in your blood
• Can sometimes create toxic by-products if the liver is damaged

Antibiotics: What They Are and How They Work

What are Antibiotics?

Antibiotics are chemical substances produced by certain fungi or bacteria that affect the working of bacterial cells. They either:

• Disrupt structure or function — damage the cell wall, cell membrane, or internal structures
• Prevent reproduction — stop bacteria from dividing and making copies

Why Don't Antibiotics Kill Viruses?

This is one of the most important things to understand. Here's why:

• Bacteria are prokaryotes: They have cell walls, ribosomes, and their own DNA. Antibiotics target these structures.
• Viruses are different: They have no cell wall, no ribosomes, and almost no cellular machinery of their own. They hijack host cell machinery to reproduce.
• Antibiotics are selective:
• Animal cells are different too:

How Do Antibiotics Actually Work?

Penicillin