20. Tetracyclins

Question 1

Tetracyclins from drug list

Answer 1

• chlortetracycline
• oxytetracycline
• tetracycline
• doxycycline
• minocycline
• tigecycline

Question 2

Classification of tetracyclins:

Answer 2

Short-acting:
- tetracycline
- oxytetracycline
- chlortetracycline

Long-acting:
- doxycycline
- minocycline

Question 3

Structure of tetracyclines:

Answer 3

4 rings -› TETRAcyclines

Question 4

Tetracyclins. Mechanism of action

Answer 4

Inhibition of protein synthesis (30S)

Question 5

Tetracyclins. Mode of action

Answer 5

bacteriostatic
at high concentrations can be bactericidal effect

Question 6

Tetracyclins. Antimicrobial spectrum

Answer 6

• all tetracyclins similar. In theory spectrum is broad but in practice RESISTANCE! (old and cheap drug -› overuse)
• both aerobic and anaerobic
• Gram+ and gram– bacteria

Mycoplasma (haemofelis) - on the surface of RBCs (cats!)
Anaplasma phagocytophilum - inside of WBCs (dogs!)
Rickettsiae (small IC bacteria)
Chlamydophiliae - drugs of choice
Wolbachia (lives inside of the heart worm)
Borellia (Lyme disease)
Bordetella bronchiseptica,
gram– fastidious bacteria

Also against some protozoa: Plasmodium, Entamoeba histolytica, Babesia and Theileria spp.

Question 7

Tetracyclins. Mechanisms of bacteria resistance

Answer 7

1. Impaired uptake into bacteia (AB can’t penetrate)
2. Active efflux (drug is pumped out from bacteria)
3. Decomposition
4. Altering binding site

Resistance is common in E. coli, Salmonella, Pasteurella multocida, Mannheimia haemolytica

Question 8

Tetracyclins. Pharmakokinetics

Answer 8

long acting TTCs (doxycycline, minocycline) can cross BBB!

Question 9

Indications and applications of tetracyclins

Answer 9

• bronchopneumonia (Bordetella bronchiseptica, gram– fastidious bacteria)
• foot diseases (mainly anaerobic bacteria)
• UTI (not really because there are better drugs, 1st choice - amoxiclav)
• metritis, mastitis

Question 10

Specific conditions when tetracyclins are indicated

Answer 10

• Lyme disease (doxycycline!)
• chlamydophilosis
• feline mycoplasmosis
• infectious keratoconjunctivitis in cattle (Moraxella bovis)
• proliferative enteropathy in horses (Lawsonia intracellularis)
• heartworm
• nocardiosis, anaplasmosis

Question 11

Tetracyclines. Side effects and toxicity

Answer 11

• GI disturbances
• Dysbacteriosis
• rapid IV: collapse
• tissue necrosis (if IM)
• yellow discolouration of the teeth
• hepatotoxicity
• nephrotoxicity
• photosensitivity