Tetracyclines Flashcards
Are Tetracyclines Bacteriostatic or Bacteriocidal?
Bacteriostatic
What is the suffix that tetracyclines can be recognized by?
-cycline
What are the 2 general classes of tetracyclines?
Older, Hydrophilic
Newer, Lipophilic
What are the drugs in the older, hydrophilic class of tetracyclines?
Tetracycline
Oxytetracycline
What are examples of the newer, lipophilic class of tetracyclines?
Doxycycline
Minocycline
Why are the newer lipophilic tetracyclines used more frequently?
Longer half-life
Broader spectra of antibacterial action
Better penetration of tissues
What bacterium are the newer lipophilic tetracyclines the drug of choice for treating?
Chlamydia
Mycoplasma
Rickettsia
Spirochete
What unique properties do tetracyclines have?
Ability to accumulate within mammalian cells
Reach organisms that hide within mammalian cells
What bacteria do tetracyclines treat that live symbiotically with heartworm and likely contributes to lung disease and renal disease seen with heartworm infection?
Wolbachia
What is the mechanism of action for Tetracyclines?
They bind to ribosomes and disrupt protein synthesis
Unlike aminoglycosides, tetracyclines do not cause bacterial destruction. What do they do instead?
Depend on the functional immune system to help them overcome a microbial infection
Are mammalian cells affected by tetracyclines?
No not at normal doses. They might be affected at higher doses
Which tetracyclines are more readily absorbed from the GI tract?
Doxycycline & Minocycline
Why are Doxycycline & Minocycline more readily absorbed from the GI tract?
More lipophilic
The hydrophilic nature of oxytetracycline & tetracycline makes them more readily able to what?
Chelate
What is chelate?
Bind to and precipitate out of a solution
Oxytetracycline & tetracycline are chelated in the presence of what?
Diet containing high amounts of dairy
Iron supplements
Oral antacids
Antidiarrheal products containing kaolin, pectin or bismuth subsalicylate
Why is Oxytetracyclone more commonly used as an injectable?
Because of its good absorption from IM sites
Which drug produces more reliable concentrations when administered PO?
Tetracycline
Why do tetracyclines and oxytetracyclines not achieve significant concentrations in the CNS or penetrate mammalian cells to reach intracellular pathologic organisms?
Because they are hydrophilic
Which drug is the preferred drug for treatment of CNS signs associated with Lyme disease?
Doxycycline
How are Oxytetracycline and tetracycline excreted?
Renal filtration and the liver (to a lesser extent)
Doxycycline and Minocycline are largely excreted by what?
The liver
What tetracycline may be reabsorbed because it chelates less with intestinal contents and can enter the systemic circulation and effect infections until it is again removed by the liver?
Doxycycline
What do the major problems of tetracyclines relate to?
Their binding with calcium and other divalent cations
What happens if tetracycline & oxytetracycline are given in developing animals between 4 and 16 weeks of age?
The teeth will develop a yellow, mottled discoloration
Besides yellowing the teeth, why else should tetracyclines and oxytetracyclines not be given to young, developing animals?
It may slow bone development
What drugs may tetracyclines interfere with the efficacy of?
Beta-lactum drugs penicillin and cephalosporins
What kind of bacteria are tetracyclines not effective against?
Anaerobic bacteria
Will not eliminate Pseudomonas infections
Tetracyclines can reduce the population of some beneficial GI tract flora and allow overgrowth of pathogenic bacteria producing what?
Superinfections
What adverse reactions do tetracyclines produce in dogs?
Diarrhea
Vomiting
Anorexia
What adverse reactions to tetracyclines are seen in cats?
Fever
Depression
Abdominal pain
What do IV injections of doxycycline in horses cause?
Cardiac arrhythmias
Collapse
Death
Does oral administration of doxycyline cause the same side effects as IV doxycycline?
No
Doxycycline powder may adhere to the esophagus causing what side effects?
Injuring the tissues, that form scar tissue with the potential to create an esophageal stricture
What form of Doxycycline is thought to be more of a risk for esophagitis and erosion due to its highly acidic nature?
Doxycycline hyclate
