Tetracyclines


Examples

Properties

  • broad spectrum

  • bacteriostatic

Mechanism of action

  • bind reversibly to 30S ribosome, blocking binding of tRNA

  • inhibit protein synthesis

Activity

Resistance

  • active efflux

    • most common cause of resistance

    • several genes responsible

  • decreased penetration

    • OmpF protein mutation can give resistance to tetracyclines, beta-lactams, quinolones, chloramphenical

  • alteration of target site

  • production of proteins protecting 30S ribosome

  • enzymatic modification

Usage

  • absorption reduced by

    • milk

    • antacids

    • calcium / iron / magnesium / zinc salts

  • stain teeth and bones so don't use in <12s, pregnant / breastfeeding women

Side Effects