An antibiotic does not identify the exact location of the bacteria causing an infection. Instead, after entering the body, the medicine is distributed through the bloodstream and reaches different tissues, where its substances act on structures or processes essential to certain bacteria.
For oral medicines, absorption begins in the digestive system before the antibiotic enters the bloodstream. The amount that reaches each part of the body depends on the properties of the drug and the patient’s condition. Its concentration and the interval between doses also affect how effectively it can control bacterial growth.
Different antibiotics work in different ways. Amoxicillin, for example, interferes with the formation of the cell wall found in susceptible bacteria. Human cells do not have this structure, although the medicine can still cause side effects, including effects on bacteria that normally live in the body. Other antibiotics act by blocking the production of proteins needed by bacteria.
This mechanism also explains why antibiotics do not treat common colds and flu. Those illnesses are caused by viruses, which have different characteristics and are not eliminated by these medicines.
The time between doses varies according to the antibiotic. A 2023 review published in Open Forum Infectious Diseases noted that, for medicines such as amoxicillin, effectiveness is linked to the period during which its concentration remains high enough to prevent the growth of susceptible bacteria. Amoxicillin may be prescribed every eight or 12 hours, while azithromycin, which remains in tissues for longer, is often taken once a day.
Delaying or forgetting doses can reduce treatment effectiveness. Inappropriate antibiotic use also contributes to bacterial resistance, making some infections more difficult to treat. Patients should follow the prescribed schedule, dosage and duration, and consult the package leaflet or a healthcare professional if they miss a dose rather than doubling the next one on their own.
Sources: CNN Brasil.