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