CSF Penetration of Antimicrobials

• Ability of antimicrobials to penetrate into CSF is dependent on:
  • age of patient (better in infants and older persons than in children and young adults)
  • degree of meningeal inflammation (↑ inflammation → ↑ penetration)
  • lipid solubility (↑ lipid solubility → ↑ penetration)
  • degree of ionization (↑ ionization → ↓ penetration)
  • molecular weight (↑ molecular weight → ↓ penetration)
  • protein binding (↑ protein binding → ↓ penetration)
  • susceptibility to active transport systems (which pump antibiotics out of the CSF)
• Bactericidal effect maximal when CSF antibiotic concentration exceeds in vitro MIC of the pathogen by 10 - 20 times.