CB5.3 — Drugs and treatments (Edexcel 1SC0)
Origins of medicines
- Aspirin: originally derived from willow bark (salicylic acid).
- Digitalis: derived from foxglove (Digitalis purpurea); treats heart conditions.
- Penicillin: discovered by Alexander Fleming in 1928 from Penicillium mould; inhibits bacterial cell wall synthesis.
Drug testing and development
New drugs undergo extensive testing before use:
- Computer modelling: test safety and efficacy virtually.
- Preclinical testing (laboratory/animals): test toxicity, dosage, efficacy.
- Clinical trials (human volunteers):
- Phase 1: small group; safety.
- Phase 2: larger group; dosage and efficacy.
- Phase 3: large randomised controlled trial.
- Double-blind trial: neither doctor nor patient knows who receives the drug or placebo → removes bias.
Antibiotic resistance
Mechanism: bacteria evolve resistance through natural selection (see CB4.1). Overuse and misuse of antibiotics accelerates this.
Solutions: only prescribe when necessary; complete the full course; develop new antibiotics; use combination therapies.
MRSA (Methicillin-resistant Staphylococcus aureus): example of a "superbug" resistant to many antibiotics.
Antibiotics vs viruses
Antibiotics only work on bacteria — they target bacterial cell walls or ribosomes. They have no effect on viruses. Antiviral drugs target virus-specific enzymes.
AI-generated · claude-opus-4-7 · v3-edexcel-combined-science