Drugs and MedicinesAQA GCSE Biology: Revision notes

Antibiotics, such as penicillin, kill infective bacteria inside the body without harming human cells.

• Specific bacteria should be treated using specific antibiotics — using the wrong antibiotic may not work
• Antibiotics cannot kill viral pathogens, because viruses reproduce inside human cells, making it difficult to target the virus without damaging the body's own tissue
• Painkillers and other medicines treat the symptoms of disease but do not kill the pathogens causing it

Historically, drugs were extracted from plants and microorganisms:

• Digitalis — a heart drug from foxgloves
• Aspirin — a painkiller originally from willow
• Penicillin — an antibiotic discovered in the Penicillium mould

Today, most new drugs are synthesised (made) by chemists in the laboratory, often based on a chemical originally found in nature, and then adapted.

Before a new drug reaches patients, it must be tested for toxicity, efficacy (whether it works) and the correct dose:

1. Preclinical testing — using cells, tissues and live animals in the laboratory
2. Clinical trials — first on healthy human volunteers, using very low doses, to check for harmful side effects; then on patients
3. Double-blind trials — some patients receive a placebo (containing no drug) so neither the patient nor doctor knows who received the real drug, reducing bias
4. Results are published only after peer review by other scientists, checking the work is valid before it is trusted

Monoclonal antibodies can deliver treatment directly to specific cells: for example, attaching a radioactive substance or toxic drug that stops cell growth, so it targets cancer cells without harming healthy tissue.

However, in practice monoclonal antibody treatments have caused more side effects than originally expected, and are not yet as widely used in medicine as scientists once hoped, so ongoing research and testing (much like for other new drugs) is needed to evaluate their advantages and disadvantages.