Many Drugs Were First Discovered in Plants and Microorganisms
Antibiotic
A medicine that kills bacteria, or stops them growing, inside the body to cure a bacterial disease; antibiotics have no effect on viruses.
- Traditionally, drugs were extracted from plants and microorganisms.
- Digitalis
- A heart drug that comes from foxgloves.
- Aspirin
- A painkiller that comes from a chemical found in willow bark.
- Penicillin
- The first antibiotic, discovered by Alexander Fleming from the Penicillium mould.
Fleming noticed that Penicillium mould on a culture plate killed the bacteria growing around it, which led to the discovery of penicillin.
Most New Drugs Are Now Synthesised, but Still Tested Hard
- Most new drugs are now synthesised by chemists in the pharmaceutical industry.
- Even so, the starting point may still be a chemical extracted from a plant or microorganism.
- Every new medicine must be tested and trialled before use, to check it is safe and effective.
- Drugs are tested for toxicity (harmful side effects), efficacy (whether the drug works) and the right dose.
Developing a new medicine can take over a decade and cost a great deal, and most possible drugs fail before they reach patients.
Preclinical Testing Uses Cells, Tissues and Animals
Preclinical testing
The first stage of testing a new drug, carried out in a laboratory on cells, tissues and then live animals, before it is given to any people.
- Preclinical testing is carried out in a laboratory.
- The drug is first tested on cells and tissues.
- Promising drugs are then tested on live animals to see how they behave in a whole organism.
- This stage checks efficacy and toxicity and gives early information about the dose.
Only drugs that pass preclinical testing are allowed to move on to being tested in people.
Clinical Trials Test the Drug on People in Stages
Clinical trial
A stage of drug testing in which a new medicine is tested on healthy volunteers and then patients to check it is safe, that it works, and to find the best dose.
- Drugs that pass preclinical testing move on to clinical trials on people.
- The drug is first given to healthy volunteers at very low doses to check it is safe.
- The dose is slowly increased to check for side effects.
- It is then given to patients with the illness to check that it works and to find the optimum dose.
Healthy volunteers are used first to check safety, before any patient is given the drug to test whether it works.
Placebos Let Scientists Compare Fairly
Placebo
A dummy treatment that contains no active drug, given to one group in a trial so the real medicine's effect can be compared fairly.
- In many trials some patients are given the drug and others are given a placebo, a dummy treatment with no active drug.
- Patients are put into the groups at random.
- Comparing the two groups shows whether it is really the drug having an effect.
The placebo often contains a treatment already in use, so patients in the trial are not left without any treatment.
Double-Blind Trials and Peer Review Remove Bias
Double-blind trial
A trial in which neither the patient nor the doctor knows who has been given the real drug or the placebo, which removes bias from the results.
- In a double-blind trial, neither the patient nor the doctor knows who has the drug and who has the placebo.
- This removes bias from the results, because expectations cannot influence what is recorded.
- Before results are published, they are checked by other scientists in a process called peer review.
- Peer review helps check the results are accurate and prevents false claims.
- Name one drug that came from a plant and one that came from a microorganism, and give their uses.
- What three things is a new drug tested for?
- What happens during preclinical testing?
- Why are healthy volunteers given the drug before patients?
- What is a double-blind trial, and why is it used?