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Pharmacological particulars
Pharmacotherapeutic group: Antibacterial for systemic use, tetracyclines.
ATCvet code: QJ01AA02
Pharmacodynamic properties
Doxycycline is a second-generation tetracycline. The product is mainly bacteriostatic; it inhibits bacterial protein synthesis by blocking the binding of transfer RNA at the messenger RNA-ribosome-complex. Doxycycline has a time-dependent concentration-enhanced effect with AUC/MIC being the main pharmacodynamic index.
Resistance is mainly mediated by efflux pumps or ribosomal protection proteins. Cross-resistance among tetracyclines is common but depends on resistance mechanisms: i.e. mutation in efflux pumps that renders resistance to tetracycline may still be sensitive to doxycycline. However, induction of the ribosomal protection proteins confers cross-resistance to doxycycline.
Bacterial species/group and origin
MIC90
Resistant (%)
Cut-off used
Pasteurella spp.:
P. multocida in cats (DE 2012)
0.25 μg/ml
P. multocida (DE 2010)
0.5 μg/ml
P. multocida in dogs (FR 2013)
15%
8 μg/ml#
P. multocida in cats (FR 2013)
11%
8 μg/ml#
Bordatella bronchiseptica:
Bordatella bronchiseptica (DE 2010-2011)
1 μg/ml
# Based on the recommendations of the French CA-SFM (Comité de l'Antibiogramme de la Société Française de Microbiologie)
Pharmacokinetic properties
After oral administration doxycycline is mainly absorbed from the duodenum and jejunum. Following oral administration, the bioavailability is >50%.
Doxycycline is widely distributed throughout the body, and can accumulate intracellularly for example in leukocytes. It is deposited in active bone tissue and teeth. Doxycycline is primarily eliminated through faeces by direct intestinal excretion and to a lesser extent by glomerular excretion and biliary secretion.