antibiotics

Antibiotics are medicines used to treat bacterial infections. They may be natural products, semisynthetic derivatives, or fully synthetic. They kill bacteria or stop their growth but are not effective against viruses. The discovery of penicillin by Alexander Fleming in 1928, followed by demonstrations in the 1940s, launched the antibiotic era and transformed medicine.

Antibiotics act by several mechanisms: inhibiting cell wall synthesis (beta-lactams, glycopeptides); inhibiting protein synthesis (macrolides, tetracyclines, aminoglycosides); inhibiting nucleic acid synthesis (fluoroquinolones, rifamycins); or blocking essential metabolic pathways (sulfonamides with trimethoprim). They can be bactericidal (kill bacteria) or bacteriostatic (halt growth) and may be broad- or narrow-spectrum.

Resistance arises via mutations, decreased permeability, efflux pumps, and enzymatic inactivation (such as beta-lactamases). Widespread or inappropriate use accelerates resistance. Antimicrobial stewardship programs seek to optimize selection, dosing, route, and duration to treat infections while reducing resistance and adverse effects.

Adverse effects include allergic reactions, digestive upset, and rare but serious events such as antibiotic-associated diarrhea or C. difficile infection. Some agents carry teratogenic risks or drug interactions. Dosing depends on pharmacokinetics; many antibiotics require adjustment in kidney or liver disease and are given orally, topically, or intravenously.

Antibiotics do not treat viral infections and should be taken only when indicated. Completing prescribed courses helps prevent relapse and resistance. Responsible use ensures these medicines remain effective for future patients.