Aminoglucòsids

Aminoglucòsids, also known as aminoglycosides, are a class of antibiotics composed of an aminocyclitol ring linked to amino sugars. They are bactericidal, primarily by binding irreversibly to the 30S ribosomal subunit and causing misreading of messenger RNA, which disrupts protein synthesis and interferes with initiation complex formation. Most are derived from soil actinomycetes such as Streptomyces and Micromonospora.

The spectrum of activity is mainly against aerobic Gram-negative bacteria, including Enterobacterales and Pseudomonas aeruginosa, with variable activity against Gram-positive cocci when used in combination with beta-lactams. They are relatively inactive against anaerobes. Resistance commonly arises from bacterial enzymes that modify the drug (acetyltransferases, nucleotidyltransferases, and phosphotransferases), mutations in the ribosomal target, or decreased uptake due to changes in membrane permeability. These mechanisms limit usefulness and underpin the preference for combination therapy in severe infections.

Clinical use involves systemic infections where synergy with beta-lactams is advantageous, such as severe pneumonia, intra‑abdominal infections, and sepsis due to Gram-negative organisms. They are also used topically and, in some cases, by inhalation for chronic Pseudomonas infections in cystic fibrosis patients. Pharmacokinetically, aminoglycosides are poorly absorbed from the gastrointestinal tract and are usually given parenterally; some formulations are used topically or by inhalation. They are primarily excreted unchanged by the kidneys, requiring dose adjustment in renal impairment. A major concern is toxicity: nephrotoxicity and ototoxicity (cochlear and vestibular), which can be dose- and duration-dependent, and rarely neuromuscular blockade. Usage is generally avoided in pregnancy unless clearly indicated.