Pharmacotherapeutic group: ophthalmologicals: antibiotics
ATCvet code: QS01AA02
Pharmacodynamic properties
Chlortetracycline hydrochloride is a first-generation tetracycline. It is a predominantly bacteriostatic antibiotic that inhibits bacterial protein synthesis by binding to the 30S subunit of the bacterial ribosome. Chlortetracycline has time-dependent as well as concentration-dependent effects with AUC/MIC being the main PK/PD parameter. Chlortetracycline has a broad spectrum including both aerobic and anaerobic Gram-positive and Gram-negative bacteria.
Four resistance mechanisms acquired by microorganisms against tetracyclines in general have been reported: decreased accumulation of tetracyclines (decreased permeability of the bacterial cell wall and active efflux), protein protection of the bacterial ribosome, enzymatic inactivation of the antibiotic and rRNA mutations (preventing the tetracycline binding to ribosome).
Tetracycline resistance is usually acquired by means of plasmids or other mobile elements (e.g. conjugative transposons).
Resistance to tetracyclines is common and has been identified in target bacterial pathogens; however, the prevalence of resistance is likely to vary widely between different locations.
Cross-resistance among tetracyclines is common.
Pharmacokinetic properties
Chlortetracycline is a non-lipophilic molecule. After topical administration in the eye, systemic absorption is expected to be minimal.