1/8 Antimicrobials Used in Lung Infection and Antiviral drugs Flashcards
Name some commonly used tetracyclines in vet med.
Tetracycline
Chlortetracycline
Oxytetracycline
Doxycycline
Minocycline
How do tetracyclines get into bacteria and work?
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
What is the mechanism of action for tetracyclines?
Act of ribosome 50s subunit, blocking the A site, preventing the bacteria from performing protein synthasis.
How are tetracyclines usually administered?
IM or Iv as oral absorption is low and food decreases absorption.
What parts of the body do tetracyclines access?
Enter most tissues and body fluids
- generally don’t get into brain
- cross placenta and get into milk
How are tetracyclines metabolised?
Minimal excretion unchanged in urine and bile
Some enterohepatic recirculation
What are some of the characteristics of mino and doxycycline?
More lipid soluble
Better penetration of into brain, ocular tissue, and bronchial secretions
Good absorption after oral administration
Both enter intestines via bile
What is the metabolism and excretion like of minocycline?
Some metabolism
Excreted in bile and faeces
What is the metabolism and excretion like of doxycycline?
No renal excretion (good for animal with renal impairment)
What type of toxicity can happen with tetracyclines?
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
What are tetracyclines used for clinically?
Useful in mized bacterial infections (broad spectrum)
Mino and doxycycline have anti-inflammatory properties
What are some Macrolides?
Erythromycin
Tilmicosin
Spiramycin
Tulathromycin
What type of bacteria do macrolides fight?
Moderate spectrum: mainly gram positive and some gram negative.
Moderate activity against anaerobes.
Bacteriostatic
What is the macrolides mechanism of action?
Act at the translocation step to inhibit it, inhibiting protein synthesis.
How do macrolides travel throughout the body?
High intracellular concentrations
Broad distribution in tissues
Don’t cross blood brain barrier and poorly in synovial fluid
Enter/concentrate in phagocytes
What actions/effect do macrolides have?
Reduce mucus production
May enhance host immune response
Anti-inflammatory actions
What are the pharmacokinetics of erythromycin?
Weak base (so trapped in acidic fluids-milk, urine)
High lipid solubility
Well distributed in tissues
Partially inactivated by hepatic metabolism
What is the toxicity of erythromycin like?
One of the safest antimicrobial drugs
Irritant- oral, IV, IM, intramammary
GI distrubance common
Serious in horse due to method of excretion
Why do you need to be cautious with tilmicosin?
Concentrated in tissues like lungs, can cause rapid depletion of Ca2+ and heart problems –> fatal!
What are some common clinical uses of macrolides?
Alternative to penicillin (penicillin sensitive animals)
Campylobacter
Respiratory disease in pigs, cattle, poultry
What is special about advance generation macrolide antibiotics?
Broader spectrum of activity
Longer half lives
Higher tissue concentrations allowing daily dosage
List some fluoroquinolones.
Norfloxacin
Enrofloxacin
Danofloxacin
Marbofloxacin
How do fluoroquinolones work?
Bacteriocidal (need high dose)
Enter bacteria through porins
What is the mechanism of action for fluoroquinolones?
Bind to nuclear enzymes, inhibiting DNA replication
What is the spectrum of activity for fluoroquinolones?
Broad, bacteriocidal
What are the pharmacokinetics for fluoroquinolones?
Partically metabolised in the liver
Parent durg and metabolites excreted in urine, bile
High urinary concentrations of parent drug
Enterohepatic recycling
What are fluoroquinolones clinically used for?
Serious gram negative infections
- UTI
- Prostate infections
- skin, soft tissue, wound infection
What are some of the toxicity/interactions cause by fluoroquinolones?
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
What are some of the mechanisms by which antiviral drugs work?
Ion channel blockers (flu A) Reverse transcriptase inhibitor (retrovirus) DNA polymerase (herpes) Neuraminidase inhibitor (Tamiflu- flu A and B)
Name a few antiviral drugs.
Aciclovir (inhibits DNA polymerase)
Amantadine & Rimantadine (blocks viral M2 ion channel- stops virus from being able to uncoat)
