Aminoglycosides

• Who discovered the first aminoglycoside, Streptomycin, and in what year?

  Waksman in 1944
• What are aminoglycosides primarily derived from?

  Actinomycetes
• What suffix do aminoglycosides obtained from Streptomyces typically have?

  mycin
• What suffix do aminoglycosides obtained from Micromonospora typically have?

  micin
• What is the primary action of aminoglycosides on mRNA?

  They cause misreading of mRNA, leading to incorrect protein synthesis.
• What is the chemical structure of aminoglycosides characterized by?

  Two aminosugars joined to one aminocyclitol moiety by glycosidic bonds.
• What is the aminocyclitol moiety commonly found in most aminoglycosides?

  1. 2- Deoxystreptamine
• What is the aminocyclitol in Streptomycin?

  Streptidine
• What are the physicochemical properties of aminoglycosides?

  They are highly polar, water-soluble, and more active in alkaline pH.
• How do aminoglycosides enter bacterial cells?

  Through passive diffusion and active transport mechanisms.
• What is the mechanism of action of aminoglycosides related to the ribosomal subunit?

  They bind to the 30S ribosomal subunit and induce misreading of the genetic code on mRNA.
• What is the result of the misreading induced by aminoglycosides?

  Wrong amino acids are incorporated into the peptide chain, eventually destroying peptide formation.
• What does the term "bactericidal" mean in the context of aminoglycosides?

  It means their effect is dose-dependent and leads to bacterial cell death.
• What are the two types of resistance mechanisms to aminoglycosides?

  1. Acquired (via plasmids or chromosomal changes)

  2. Natural (inherent)
• What is one way bacteria can acquire resistance to aminoglycosides?

  By altering the bacterial outer surface to decrease drug penetration.
• What is a natural resistance mechanism of anaerobes to aminoglycosides?

  They lack the energy-dependent transport mechanism that concentrates the drug in the bacterial cell.
• How is aminoglycoside absorption when given orally?

  Extremely poor
• What happens to aminoglycosides when given intramuscularly?

  They are rapidly absorbed and reach therapeutic levels in circulation within 2-1 hours.
• Why do aminoglycosides have minimal distribution inside cells?

  Because they are highly polar compounds and insoluble in lipids.
• Where do aminoglycosides have exceptional affinity in the body?

  Renal cortex tissue
• What is the primary route of elimination for aminoglycosides?

  Renal elimination, primarily unchanged through glomerular filtration.
• What is the half-life (T½) of most aminoglycosides?

  1. 3 hours
• What is the half-life (T½) of Streptomycin?

  About 5 hours
• What is the antimicrobial spectrum of aminoglycosides?

  • Mainly used to treat Gram-negative infections
  • Some Gram-positive bacteria are also affected
• What is the clinical use of Streptomycin?

  It is used to treat mycobacterial infections such as tuberculosis (TB) and leptospirosis.
• Why is Neomycin used topically?

  Because it is toxic when used systemically.
• What is the clinical use of Gentamicin?


  It is used to treat severe Gram-negative infections resistant to common drugs.
• What makes Amikacin a good alternative to Gentamicin?

  It is resistant to aminoglycosidases.
• What is the clinical use of Tobramycin?

  It is similar to Gentamicin in its uses.
• What is the significance of Netilmicin in clinical use?

  It may work in situations where bacteria are resistant to Gentamicin and Tobramycin.
• What are the main toxicities associated with aminoglycosides?

  1. Ototoxicity

  2. Nephrotoxicity

  3. Neuromuscular blockade(curare-like effect)

  4. Hypersensitivity (rarely seen)
• What does a small therapeutic index (TI) indicate about aminoglycosides?

  It indicates that toxicity can easily manifest.
• How does ototoxicity occur with aminoglycosides?

  Drug accumulation in the ear leads to selective destruction of hearing receptors, causing tinnitus and deafness.
• What is nephrotoxicity in the context of aminoglycosides?

  It is the accumulation of the drug in proximal tubule cells leading to renal impairment, which is reversible upon withdrawal.
• What should be monitored during aminoglycoside treatment to prevent nephrotoxicity?

  Drug serum levels
• What is the effect of aminoglycosides on neuromuscular function?

  They can cause a blockade leading to transient paralysis of skeletal muscles.
• Who are individuals at risk for neuromuscular blockade when using aminoglycosides?

  Patients with myasthenia gravis and those given neuromuscular blockers during surgery.
• How can neuromuscular blockade caused by aminoglycosides be reversed?

  By calcium replacement therapy.