Antibiotics: the complete guide to getting your treatment right

Antibiotics are one of the greatest advances in modern medicine — and one of the most misused medicines in the world. In many countries, over-the-counter antibiotic use remains common despite regulations requiring prescriptions. Many people still do not understand how antibiotics work, what they are actually for, and why how you take them matters as much as which one you take.

What antibiotics do — and what they don't

Antibiotics are substances that fight bacteria. They work in different ways depending on their class: some destroy the bacterial cell wall, like penicillins; others interfere with the synthesis of proteins essential for the microorganism's survival, like tetracyclines. The fundamental point is that antibiotics have absolutely no effect on viruses. The flu, the common cold, covid-19 and most cases of pharyngitis and bronchitis are caused by viruses. Taking an antibiotic for these conditions does not speed up recovery, does not relieve symptoms, and still exposes the patient to side effects with no therapeutic benefit.

Why you must finish the full course — every time

This is the golden rule of antibiotics — and the most frequently broken one. When you take antibiotics for a few days and start feeling better, it means the weakest bacteria, most sensitive to the medicine, have been eliminated. The more resistant ones are still there, only temporarily suppressed. If you stop treatment before the prescribed period, those bacteria survive, reproduce and can cause a more intense infection that is harder to treat — and can be passed on to other people.

Even more seriously: when exposed to an antibiotic for an insufficient period to fully eliminate them, bacteria can develop resistance mechanisms. This is how superbugs are created — strains that have developed resistance to multiple antibiotics. The World Health Organization classifies antimicrobial resistance as one of the greatest threats to global health in the 21st century.

Timing: why getting it right makes all the difference

Each antibiotic is designed to maintain a minimum blood concentration sufficient to eliminate bacteria. This minimum effective concentration needs to be maintained continuously throughout treatment. When you delay or skip a dose, that concentration drops below the effective level, giving bacteria a window of time to recover and eventually develop resistance. If the prescription says "every 8 hours", that means three doses distributed as evenly as possible across 24 hours.

Common side effects and how to deal with them

• Diarrhoea and intestinal discomfort: the most common side effects of virtually all antibiotics. They occur because the medicine eliminates not only pathogenic bacteria but also part of the healthy intestinal microbiota. Probiotics with Lactobacillus taken two to three hours after the antibiotic can help minimise this effect.
• Candidiasis: without beneficial bacteria to compete with, fungi like Candida can proliferate. Vaginal candidiasis is particularly common in women during or after treatment with broad-spectrum antibiotics.
• Photosensitivity: especially common with tetracyclines and fluoroquinolones. The skin becomes more sensitive to UV radiation. Use sunscreen and avoid excessive sun exposure during treatment.
• Allergic reactions: more frequent with penicillins and cephalosporins. They can range from mild hives to serious anaphylactic reactions. Any skin reaction after starting an antibiotic requires immediate contact with a doctor.

What to do with leftover antibiotics

Never keep leftover antibiotics to use for a future infection. Antibiotics are prescribed for specific infections, caused by specific types of bacteria, at specific doses and for specific periods. What worked for a urinary tract infection may be completely ineffective — or even harmful — for a throat infection. Take remaining tablets to a medicine disposal point at a pharmacy or health centre. Never throw them in the regular bin or dispose of them down the sink or toilet.