Antibiotics, painkillers and drug development

Biology · Infection and response. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.

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The idea

Antibiotics, such as penicillin, are medicines that kill bacteria inside the body. They do not kill viruses. Viruses live and reproduce inside body cells, so it is hard to make a drug that destroys the virus without damaging the cell too. Painkillers only treat the symptoms. The pathogens are still there.

Some bacteria mutate so that an antibiotic no longer kills them. These resistant strains, such as MRSA, survive and spread. The more antibiotics are used, the faster this happens.

Every new drug is tested for toxicity (is it safe?), efficacy (does it work?) and dose. Testing starts in the laboratory and then moves to people in clinical trials.

Rules to remember

Antibiotics kill bacteria only. A specific antibiotic is used for a specific bacterium.
Painkillers relieve symptoms but do not kill pathogens.
To slow down resistance: no antibiotics for viral or mild infections, and patients finish the whole course.
Drug sources: digitalis (a heart drug) from foxgloves, aspirin from willow, penicillin from the Penicillium mould (Alexander Fleming).
Preclinical testing: on cells, tissues and live animals, before any person takes the drug.
Clinical trials: very low doses to healthy volunteers first (to check safety), then to patients to find the optimum dose.
Double blind trial: neither the patients nor the doctors know who has the drug and who has the placebo.

Common mistake

Writing that the person becomes resistant or immune to the antibiotic. It is the bacteria that become resistant, not the patient.

Worked example

In a trial, 60% of patients given a new drug feel better. In a second group given a placebo, 25% feel better. Why does the trial need the placebo group?

A placebo looks like the real medicine but contains no drug.
Some people feel better just because they think they are being treated (here 25%).
Comparing the groups shows the effect of the drug itself: 60% − 25% = 35% more patients improved.

Answer: The placebo group is a control. It shows how much of the improvement is really caused by the drug.

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