Pharmacology - lipophilic antibacterial families 1 Flashcards
What does metronidazole have good activity against?
- Metronidazole only works against anaerobes
- Used to treat protozoa, giardia and trichomonas
What are tetracyclines effective against?
- They are a broad spectrum, however only have some activity against all 4 quadrants
- Considered to be bacteriostatic (kills bacteria)
Which drugs in the tetracycline family are hydrophilic?
- Tetracycline
- Oxytetracycline
- chlortetracycline
Which drugs in the tetracycline family are lipophilic?
- Doxycycline
- minocycline
Pharmacokinetics of hyrophilic tetracyclines (tetracycline, ocytetracycline and chlortetracycline).
Variable absorption from GIT – they chelate with polyvalent cations (Ca2+, Mg2+, Fe2+, Al3+ etc) in git – reduces doxycycline oral absorption binds to cations if given orally. For example, if given to a young animal that is drinking milk then it will bind to the Ca in the milk and wont be absorbed in the GIT
poor tissue distribution – can’t penetrate BBB
Primarily renal excretion (60:40 renal : hepatic)
Pharmacokinetics of lipophilic tetracyclines (doxycycline and minocycline).
Good absorption from GIT‐ generally well absorbed with food but will also chelate with polyvalent cations
Excellent tissue distribution
Primarily hepatic excretion
List some adverse effects of tetracyclines
- Possible tissue irritant - Tissue damage at injection site
- Idiosyncratic GIT disturbances
- Chelate calcium – in children with emerging adult teeth can discolour teeth (DOES NOT APPLY TO
- DOXYCYCLINE OR MINOCYCLINE)
- Alteration of intestinal flora particularly in mature horses – enterocolitis
- May cause hepatic damage - hepatogenous photosensitisation
Are there any non-antibacterial actions of tetracyclines?
Yes:
- prophylaxis and treatment of malaria
- anti-inflammatory effects (antiproteolytic properties [inhibits collagenase], suppresses neutrophil activity, may inhibit phospholipase A2 activity and block prostaglandin synthesis
What are phenicols effective against?
Some activity against gram +ve aerobes, gram ‐ ve aerobes, Anaerobes, Penicillinase ‐ producing Staphylococcus plus chlamydophilia and rickettsia
What is the mechanism of actions of phenicols?
- inhibits peptidyl transferase required for bacterial protein synthesis
What drugs are in the phenicols family?
- Chloramphenicol
- Florfenicol
Which phenicol can be used safely in production animals and why would we need to use it?
Florfenicol - can be used to treat bovine resp disease, porcine resp disease and footrot in sheep.
There are still withholding periods (cattle 42 days and pigs 12 days)
What is centiofur effective against?
- Some activity against Gram + ve Aerobes (Streptococci highly susceptible, Enterococci resistant), anaerobes, Penicillinase ‐ producing Staphylococcus
- Good activity against Gram ‐ ve Aerobes (except Enterobacter & Serratia)
How does administantion of centiofur differ in dogs and horses and cows?
- 1x injection IM in horses and cows
- Daily sub-cut injections in dogs
Is there a withholding period for cows given centiofur?
yes 24-72h
What are macrolides effective against?
- Good activity against gram +ve aerobes, anaerobes, penicillinase – producing staphylococcus, Actinobacillus, Brucella, Campylobacter, Pasteurella spp., mycoplasma, chlamydophilia and chlamydia.
- NO activity against enterobacterales
What macrolides are used in dogs, cats and people?
- Ezythromycin
- Azithromycin
- Clarithromycin
- Roxithromycin
- Spiramycin (when used with metronidazole)
What macrolides are given to production animals?
Tulathromycin, tylosin and tilmicosin
What is the mechanism of action of macrolides?
o Inhibits protein synthesis by reversibly binding to 50S ribosome subunit.
o Resulting in premature detachment of incomplete polypeptide chains
What are lincosamides effective against?
- Good activity against Many gram + ve aerobes, Anaerobes, Many penicillinase ‐ producing Staphylococcus, Campylobacter jejuni
- NO activity against enterobacterales
What drugs are in the lincosamides family?
Clindamycin and lincomycin
What is a complication observed in cats given lincosamides?
If administered orally to cats, can result in oesophagela inflammation - needs to be administered with water
What is clindamycin used to treat?
Used to treat neospora, toxoplasmosis, anaerobic infections
What are the adverse effects seen with lincomycin?
- Lincomycin can result in a serious diarrhoea in people, horses, rabbits and other herbivores – (relatively) non‐ toxic to dogs, cats, pigs, poultry
- Risk of oesophageal stricture in cats with oral tx So administer with a ‘water swallow’.
