2016B11 a) Briefly describe the bactericidal activity of gentamicin. Explain why it is usually administered as a single daily dose.
b) Describe the potential toxic effects of gentamicin.

 

Mechanism

·  Bactericidal

·  Irreversibly bind 30S subunit of ribosome -> mRNA mistranslation -> abnormal proteins -> cell dysfunction

·  ↓Multiplication and cell death

Reasons for daily dose

·  Killing ∝ peak concentration (cf. time above MIC)

·  Post-antibiotic effect

·  ↓Frequency -> ↓risk nephrotoxicity

Nephrotoxicity

·  Occurs in 10-25%

·  ↑Risk if ↑frequency of dose, ↑age, CKD, dehydrated, contrast load, other nephrotoxins

·  May be reversible

Ototoxicity

·  Vestibular dysfunction, deafness

·  Often irreversible

·  1 in 10,000 risk

·  ↑Risk if ↑peak concentration

·  ↑dose

·  ↑injection rate

Muscle weakness

·  Potentiates non-depolarising relaxants

o Antagonises pre-synaptic VDCC

o Blocks post-synaptic VDNaC