Tetracyclines - antimicrobial

Question 1

What is the MOA of tetracyclines?

Answer 1

binds to ribosomes and inhibits protein synthesis

Question 2

Use indications for tetracyclines?

Answer 2

gram -ve and gram +ve
aerobes (but not pseudomonas)
Active against chlaymida, mycoplasma, rickettsia

• one of the most commonly used antibiotic classed for production animals
• Gold standard against chlamydia

-Other uses: SA respiratory disorders, avian chlamydophilosis

• Give deep IM as is painfil
• in horses give IV

Question 3

Species application?

Answer 3

= production animals, horses, birds (can penetrate air sacs)

Question 4

Side effects/contraindications?

Answer 4

• variable effectiveness against anaerobes
• chelates anions - can bind to Ca, so should be given on an empty stomach if given PO
• chelation can cause tooth enamel discolouration in young animals
• out of date solutions are toxic
• use parenterally in ruminants and horse to avoid dsymbiosis. Avoid giving PO anyway as can cause GIT upset
• light sensitive
• high amount of real metabolism so any changes in renal function can cause accumulation

Question 5

PK quirks

Answer 5

• excellent distribution, large Vd - need loading dose
• long half life - 12 hours
• 50% hepatic metabolism, 50% renal metabolism (Doxycycline is excreted by SI)

Question 6

Representative drugs

Answer 6

Tetracycline and oxytetracycline –> hydrophilic –> good absorption from IM.

Doxycycline –> lipophilic - better oral absorption

-long acting formulas

Question 7

bactericidal/static?

time/concentration?

Answer 7

bacteriostatic (requires functioning immune system) - time dependant