Macrolides

Question 1

What are the 14-member ring macrolides?

Answer 1

Erythromycin, Clarithromycin

Question 2

What are the 15-member ring azalides?

Answer 2

Azithromycin, Gamithromycin

Question 3

What is the 15-member ring triamilide?

Answer 3

Tulathromycin

Question 4

What are the 4, 16- member rings?

Answer 4

Tylosin, Tilmicosin, Tylvalosin, Tildipirosin

Question 5

Are these compounds acidic or basic? In what pH will they ionized?

Answer 5

Basic (7.1+)

All will ionize in acidic environment (rumen)

Question 6

Are macrolides bacteristatic or bactericidal?

Answer 6

Normally bacteristatic but some now bactericidal

Question 7

How do macrolides work?

Answer 7

Inhibition of protein synthesis

Question 8

What is the spectrum of veterinary macrolides?

Answer 8

Anaerobes: +++++
Gram + aerobes: +++++
Gram - aerobes: ++

Question 9

Are macrolides active against rhodococcus? Mycoplasma?

Answer 9

Yes

Tylosin & tulathromycin

Question 10

Which macrolides are used for rhodococcus? What combination is regularly used?

Answer 10

Azithromycin/erythromycin-rifampin

Question 11

Why is Tilmicosin not effective against mycoplasma?

Answer 11

Mycoplasma bovis MIC is to high & Tilmicosin is not clinically effective

Question 12

What is another notable effect of macrolides unrelated to their antimicrobial activity?

Answer 12

Anti-inflammatory

Question 13

Which macrolides have prokinetic effects on the GI?

Answer 13

14 (Erythromycin, clarithromycin) and 16-member rings (tylosin, tilmicosin, tylvalosin, tildipirosin)

Question 14

Cross-resistance to other macrolides is common, what other antimicrobial is it common for bacteria to be resistant to if also resistant to a macrolide?

Answer 14

Lincosamides

Question 15

What is the route of administration for Tilmicosin? Why?

Answer 15

SQ ONLY
IV is fatal!
IM is extremely irritating

Question 16

Why should you never give systemic tilmicosin to swine?

Answer 16

Fatal

Question 17

Is tilmicosin available as a top dress? Which animal(s)?

Answer 17

Yes, swine & cattle

Question 18

Is oral tilmicosin the only way it can be delivered to swine?

Answer 18

Yes because it’s fatal

Question 19

Tylosin is labeled for IM administration in what animal?

Answer 19

Cattle but IV and SQ use has occured

Question 20

Tulathromycin is labeled for SQ use in what species? IM?

Answer 20

SQ in cattle

IM in swine

Question 21

Why do tissues often have higher conceontrations of macrolides than serum?

Answer 21

Macrolides concentrate in tissues

Question 22

Which cell specifically do very large amounts of macrolides accumulate in?

Answer 22

Leukocytes

Question 23

What allows macrolides to accumulate so readily in tissue?

Answer 23

High intracellular penetration

Question 24

Do macrolides reach high concentrations in CSF

Answer 24

No despite high lipid solubility

Question 25

What is the standard Vd for macrolides?

Answer 25

> 1 L/kg

Question 26

Do macrolides have good oral bioavailability?

Answer 26

Yes

Question 27

What is the primary route of elimination of macrolides?

Answer 27

Bile/hepatic

Question 28

What is the half-life of IV vs SQ tulathromycin in cattle?

Answer 28

65 IV & 92 SQ | USE SQ!

Question 29

What is the elimination half-life of azithromycin in cats/dogs?

Answer 29

30 hours (dogs 29)

Question 30

What is the Vd for azithromycin in dogs?

Answer 30

12 L/kg

Question 31

What is the oral bioavailability of azithromycin in the dog? cat?

Answer 31

100% dog | 60% cat

Question 32

What is the most important concern relating to efficacy regarding serum levels?

Answer 32

Time above MIC

Question 33

What is the efficacy of azithromycin/clarithromycin most closely linked to?

Answer 33

Peak concentration

Question 34

Macrolides (specifically erythromycin) can interact with which system that changes the pharmocodynamics of other drugs? How does it change the pharmacodynamics of these drugs?

Answer 34

Cytochrome P 450 | Causes decreased elimination because it is a CP450 substrate

Question 35

A low dose of what can be given to a horse to "start its gut"? Why?

Answer 35

Erythromycin because it is a prokinetic

Question 36

Rectal edema and prolapse has been associated with which macrolides in swine?

Answer 36

Tylosin & erythromycin

Question 37

Which macrolide may commonly cause GI upset in cats and dogs?

Answer 37

Erythromycin

Question 38

Why is it not advisable (generally) to use macrolides in horses or rabbits?

Answer 38

GI effects

Question 39

Erythromycin has caused death in horses due to what?

Answer 39

Clostridium difficile infection

Question 40

What is the issue with IM injection sites in food animals & macrolides?

Answer 40

Prolonged & extensive tissue blemishes because its caustic That's why you use it SQ

Question 41

Erythromycin can cause this in 2 - 4 month old foals?

Answer 41

hyperthermia

Question 42

Tilmicosin is fatal when given to cattle via which route?

Answer 42

IV

Question 43

Can you use Tilmicosin in goats?

Answer 43

Not a good idea, has been fatal

Question 44

At what administration of Tilmicosin IM will pigs die?

Answer 44

20 mg/kg IM

Question 45

What 2 domestic species should you never use Tilmicosin in?

Answer 45

Horses & rabbits

Question 46

Which food animals should you not use Tilmicosin in due to withdrawal time? How long is this withdrawal time?

Answer 46

Dairy cows | 15 - 29 day milk residue

Question 47

Why is it not advisable to use Tilmicosin in dairy cattle?

Answer 47

There is no label for dairy cows so there is not acceptable residue level

Question 48

Why sould you not use Tlmicosin in an automatic syringe?

Answer 48

Can inject too much and kill an animal or yourself

Question 49

What is the cause of OD deaths due to Tilmicosin?

Answer 49

Cardiovascular toxicity due to Ca+ channel block