Question
Write in detail on the mechanism of action, uses, and adverse effects of aminoglycoside antibiotics.
Answer
Aminoglycosides are bactericidal antibiotics active mainly against aerobic Gram-negative organisms.
Mechanism of action: bind the bacterial 30S ribosomal subunit, causing misreading of mRNA codons and blocking translocation — producing abnormal/nonfunctional proteins and inhibiting protein synthesis, bactericidal. Uptake requires an oxygen-dependent transport process, explaining their lack of activity against anaerobes.
Examples: Gentamicin, Amikacin, Streptomycin, Tobramycin.
Uses: severe Gram-negative infections (often combined with a beta-lactam for synergy — cell-wall damage improving aminoglycoside penetration), tuberculosis (streptomycin, second-line), enterococcal endocarditis (combined with a beta-lactam).
Adverse effects: nephrotoxicity (reversible, from proximal tubular accumulation via a saturable uptake process), ototoxicity (often irreversible — vestibular and/or cochlear), neuromuscular blockade at high doses (particularly relevant with concurrent neuromuscular blockers). Once-daily, extended-interval dosing exploits their concentration-dependent bactericidal killing and genuine post-antibiotic effect, and also reduces nephrotoxicity risk by allowing a trough period for renal tubular clearance between doses.