1/8 Antimicrobials Used in Lung Infection and Antiviral drugs

Question 1

Name some commonly used tetracyclines in vet med.

Answer 1

Tetracycline
Chlortetracycline
Oxytetracycline

Doxycycline
Minocycline

Question 2

How do tetracyclines get into bacteria and work?

Answer 2

Diffuse across outer cell membrane
Active carrier mediated process through inner cell membrane
Bind reversibly to bacterial ribosome
Inhibit bacterial protein systhesis

Bacteriostatic (stop growth) broad spectrum antimicrobials

Question 3

What is the mechanism of action for tetracyclines?

Answer 3

Act of ribosome 50s subunit, blocking the A site, preventing the bacteria from performing protein synthasis.

Question 4

How are tetracyclines usually administered?

Answer 4

IM or Iv as oral absorption is low and food decreases absorption.

Question 5

What parts of the body do tetracyclines access?

Answer 5

Enter most tissues and body fluids

• generally don’t get into brain
• cross placenta and get into milk

Question 6

How are tetracyclines metabolised?

Answer 6

Minimal excretion unchanged in urine and bile

Some enterohepatic recirculation

Question 7

What are some of the characteristics of mino and doxycycline?

Answer 7

More lipid soluble
Better penetration of into brain, ocular tissue, and bronchial secretions
Good absorption after oral administration
Both enter intestines via bile

Question 8

What is the metabolism and excretion like of minocycline?

Answer 8

Some metabolism

Excreted in bile and faeces

Question 9

What is the metabolism and excretion like of doxycycline?

Answer 9

No renal excretion (good for animal with renal impairment)

Question 10

What type of toxicity can happen with tetracyclines?

Answer 10

Broad spectrum suppression of intestinal flora can lead to superinfection with resistant bugs.
Liver damage if renally impaired animal
Deposited is sites of ossification and teeth

Question 11

What are tetracyclines used for clinically?

Answer 11

Useful in mized bacterial infections (broad spectrum)

Mino and doxycycline have anti-inflammatory properties

Question 12

What are some Macrolides?

Answer 12

Erythromycin
Tilmicosin
Spiramycin
Tulathromycin

Question 13

What type of bacteria do macrolides fight?

Answer 13

Moderate spectrum: mainly gram positive and some gram negative.

Moderate activity against anaerobes.

Bacteriostatic

Question 14

What is the macrolides mechanism of action?

Answer 14

Act at the translocation step to inhibit it, inhibiting protein synthesis.

Question 15

How do macrolides travel throughout the body?

Answer 15

High intracellular concentrations
Broad distribution in tissues
Don’t cross blood brain barrier and poorly in synovial fluid
Enter/concentrate in phagocytes

Question 16

What actions/effect do macrolides have?

Answer 16

Reduce mucus production
May enhance host immune response
Anti-inflammatory actions

Question 17

What are the pharmacokinetics of erythromycin?

Answer 17

Weak base (so trapped in acidic fluids-milk, urine)
High lipid solubility
Well distributed in tissues
Partially inactivated by hepatic metabolism

Question 18

What is the toxicity of erythromycin like?

Answer 18

One of the safest antimicrobial drugs
Irritant- oral, IV, IM, intramammary
GI distrubance common
Serious in horse due to method of excretion

Question 19

Why do you need to be cautious with tilmicosin?

Answer 19

Concentrated in tissues like lungs, can cause rapid depletion of Ca2+ and heart problems –> fatal!

Question 20

What are some common clinical uses of macrolides?

Answer 20

Alternative to penicillin (penicillin sensitive animals)
Campylobacter
Respiratory disease in pigs, cattle, poultry

Question 21

What is special about advance generation macrolide antibiotics?

Answer 21

Broader spectrum of activity
Longer half lives
Higher tissue concentrations allowing daily dosage

Question 22

List some fluoroquinolones.

Answer 22

Norfloxacin

Enrofloxacin
Danofloxacin
Marbofloxacin

Question 23

How do fluoroquinolones work?

Answer 23

Bacteriocidal (need high dose)

Enter bacteria through porins

Question 24

What is the mechanism of action for fluoroquinolones?

Answer 24

Bind to nuclear enzymes, inhibiting DNA replication

Question 25

What is the spectrum of activity for fluoroquinolones?

Answer 25

Broad, bacteriocidal

Question 26

What are the pharmacokinetics for fluoroquinolones?

Answer 26

Partically metabolised in the liver
Parent durg and metabolites excreted in urine, bile
High urinary concentrations of parent drug
Enterohepatic recycling

Question 27

What are fluoroquinolones clinically used for?

Answer 27

Serious gram negative infections

• UTI
• Prostate infections
• skin, soft tissue, wound infection

Question 28

What are some of the toxicity/interactions cause by fluoroquinolones?

Answer 28

Relatively safe
Erosion of weight-bearing cartilage
Clearance of other drugs through liver may be reduced
Some CNS issues may occur
Ocular problems in cats

Question 29

What are some of the mechanisms by which antiviral drugs work?

Answer 29

Ion channel blockers (flu A)
Reverse transcriptase inhibitor (retrovirus)
DNA polymerase (herpes)
Neuraminidase inhibitor (Tamiflu- flu A and B)

Question 30

Name a few antiviral drugs.

Answer 30

Aciclovir (inhibits DNA polymerase)

Amantadine & Rimantadine (blocks viral M2 ion channel- stops virus from being able to uncoat)