Discovering and developing drugs
Traditionally drugs were extracted from plants and microorganisms.
There are many examples of this such as Penicillin which was discovered by Alexander Fleming.
| Organism | Drug | What the drug treats |
|---|---|---|
| Foxglove plant | Digitalis | Heart failure |
| Bark of willow tree | Aspirin | Painkiller |
| Penicillium mould | Penicillin | Antibiotic, treats bacterial infections |
The starting point is often a chemical extracted from a plant.
Once the active ingredient within the plant has been identified then most new drugs are synthesised by chemists in the pharmaceutical industry.
Why new drugs are tested?
New drugs are extensively tested for toxicity, efficacy and dose.
To check the drug is safe and not toxic.
To check its efficacy to see if it is effective (works)
To find the optimal dose, or lowest dose that is effective.
Peer Review.
Before the results of drug testing and clinical trials are released to doctors, scientists or the public, they must be checked by other independent scientists to make sure the research is:
Valid
Reliable
Accurate
Not biased
Reported honestly
This checking process is called peer review.
Only after this scrutiny can the results be published in a scientific journal.
Drug Testing
There are two main stages to testing drugs.
1.Preclinical testing
2. Clinical trials
Preclinical testing
Preclinical testing is done in a laboratory using cells, tissues and live animals.
Cells and tissues
The drugs are first tested on cells or isolated tissues in a lab.
Used to check toxicity and whether it seems to have the desired effect.
Those that pass, progress to the next stage. Any that fail are discarded.
Live animals
The small number of drugs that pass the previous stage are now tested on animals to check safety and how the drug behaves in a whole organism.
Clinical trials
Clinical trials is when the drug is trialled in humans. Only drugs that pass all of the previous stages will be tested on humans. There two main stages to clinical trials.
a) Healthy volunteers
Very low doses of the drug are given to healthy volunteers. This is mainly to check for side effects and basic safety.
b) Patients
Once the drug has passed all of the previous stages the drug is tested on a group of patients. The dose is gradually increased, to test effectiveness and to find the optimum dose.
Double blind trials.
The people in the trial are split into two groups.
One group will receive the trial drug, whilst the other group will receive a placebo(dummy drug).
Neither the patient nor the doctor knows who has what (double blind). This is designed to prevent bias.
Information about who received the real drug and who received the placebo is only revealed after the trial has finished.
Practice Questions
1.State three reasons why it is important to test drugs
2. What is often the original source for a drug?
3. What is a double blind trial?