Tetracyclines

Antibacterials

Docycycline.

bind 30S subunit → aminoacyl-tRNA is blocked from binding to ribosome acceptor site → inhibition of bacterial protein synthesis (bacteriostatic effect)

poor

• Renal

• Doxycycline: only gastrointestinal elimination (doxycycline is the only tetracycline that is not contraindicated in patients with renal failure)

• Bacteria that lack a cell wall (e.g, Mycoplasma pneumoniae, Ureaplasma)

• Intracellular bacteria, such as Rickettsia, Chlamydia, or Anaplasma (tetracyclines accumulate intracellularly and are, therefore, effective against intracellular pathogens)

• Borrelia burgdorferi

• Other: Ehrlichia, Vibrio cholerae, Francisella tularensis

• Cutibacterium acnes (topical tetracycline is used to treat acne) [31]

• Community-acquired MRSA (doxycycline)

• Oral tetracyclines should not be taken with substances that contain large amounts of Ca2+, Mg2+, or Fe2+ (e.g., milk, antacids, iron supplements, respectively) because divalent cations inhibit the intestinal absorption of tetracyclines.

• CNS penetration is limited

• Hepatotoxicity

• Deposition in bones and teeth → inhibition of bone growth (in children) and discoloration of teeth

• Damage to mucous membranes (e.g., esophagitis, GI upset)

• Photosensitivity: drug or metabolite in the skin absorbs UV radiation → photochemical reaction → formation of free radicals → damage to cellular components → inflammation (sunburn-like) [32]

• Degraded tetracyclines are associated with Fanconi syndrome. [33]

• Rarely: pseudotumor cerebri

• Children < 8 years of age (except doxycycline) [35]

• Pregnant women

• Breastfeeding women

• Patients with renal failure (except doxycycline)

• Cautious use in patients with hepatic dysfunction

Plasmid-encoded transport pumps increase efflux out of the bacterial cell and decrease uptake of tetracyclines.