Discovering and Testing New Drugs

Discovering New Drugs

Some plants produce chemicals to kill pests and pathogens. These chemicals can also be used to treat diseases. In the past, drugs were often extracted from plants and microorganisms. For example:

  • Aspirin originates from willow trees, and it is used as a painkiller
  • Digitalis originates from foxglove plants, and it is used to treat certain heart conditions
  • Alexander Fleming discovered the antibiotic penicillin from the Penicillium mould

Most new drugs are synthesised by scientists at pharmaceutical companies. However, the starting point is often still a chemical extracted from a plant.

Testing New Drugs

Scientists are constantly developing new drugs to treat disease. However, a drug cannot reach the market without rigorous testing. A lack of strict testing has caused many issues in the past.

Thalidomide was a drug used in the 1950s and 1960s to treat a range of conditions, including colds, flu, pneumonia and morning sickness. However, it was later found to cause birth defects.

Since then, governments and medical authorities have changed the way drugs are tested and approved around the world. For example, drugs intended for human use cannot be approved based solely on animal testing.

New drugs are developed all the time. There are three main factors taken into account when producing drugs:

  • Toxicity – Making sure the drugs don’t have harmful side effects
  • Efficacy – Otherwise known as effectiveness, so making sure the drug works
  • Dose Finding out the correct dose required for the drug to work, with minimum side effects. This is the lowest dose that still provides the desired effect, as too much of a drug can cause damage to humans.

Stages of Testing

The three main stages of testing are:

1. Preclinical testing – Cells and tissues

2. Preclinical testing – Animals

3. Clinical trials

Preclinical testing – Cells and tissues

The first stage of testing new drugs is called preclinical testing and there are two parts. Preclinical testing is not carried out on humans because many drugs at this stage can be very toxic.

The first stage of preclinical testing is carried out on cells and tissues in a laboratory, using computer models. Most drugs fail this stage as they damage cells or they are not effective.

  • This stage tests the efficacy and toxicity of the drug

Preclinical testing – Animals

Drugs that pass the first stage of preclinical testing are tested on whole animals. In 1998, testing cosmetic products on animals was banned in the UK. However, all new medicines in the UK require animal testing before they can be tested on humans.

  • This stage tests the efficacy, toxicity and dose of the drug

Clinical trials

Once preclinical tests are complete, the drug undergoes clinical testing on humans. In the first stage of clinical testing, a low dose is administered to healthy volunteers to check if the drug is safe for humans. If the drug is safe, then the clinical testing continues.

In the second stage, healthy patients are given different doses of the drug to determine the optimal dose. This is the best dose to treat the disease with the minimum side effects.

In clinical trials, patients are split into two groups. One group receives a placebo and the other receives the actual drug. Placebos are drugs that look like the drug being tested but have no active ingredient and therefore have no effect. They are used to observe and study the effectiveness of new drugs.

Some patients will get better when given a placebo. This is because it may affect how the patient perceives their condition, which can improve the patient’s symptoms.

The tests carried out in clinical trials can either be single-blind or double-blind

  • Single-blind trial: Only the doctor knows whether or not the patient is receiving the drug
  • Double-blind trial: Neither the patient nor the doctor knows whether or not the patient is receiving the drug

Double-blind trials help eliminate any biases the doctors may have when recording the results. All results must be peer-reviewed by other scientists to ensure repeatability.

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