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
