Pharmacology - lipophilic antibacterial families 1

Question 1

What does metronidazole have good activity against?

Answer 1

• Metronidazole only works against anaerobes
• Used to treat protozoa, giardia and trichomonas

Question 2

What are tetracyclines effective against?

Answer 2

• They are a broad spectrum, however only have some activity against all 4 quadrants
• Considered to be bacteriostatic (kills bacteria)

Question 3

Which drugs in the tetracycline family are hydrophilic?

Answer 3

• Tetracycline
• Oxytetracycline
• chlortetracycline

Question 4

Which drugs in the tetracycline family are lipophilic?

Answer 4

• Doxycycline
• minocycline

Question 5

Pharmacokinetics of hyrophilic tetracyclines (tetracycline, ocytetracycline and chlortetracycline).

Answer 5

 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)

Question 6

Pharmacokinetics of lipophilic tetracyclines (doxycycline and minocycline).

Answer 6

 Good absorption from GIT‐ generally well absorbed with food but will also chelate with polyvalent cations
 Excellent tissue distribution
 Primarily hepatic excretion

Question 7

List some adverse effects of tetracyclines

Answer 7

• 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

Question 8

Are there any non-antibacterial actions of tetracyclines?

Answer 8

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

Question 9

What are phenicols effective against?

Answer 9

Some activity against gram +ve aerobes, gram ‐ ve aerobes, Anaerobes, Penicillinase ‐ producing Staphylococcus plus chlamydophilia and rickettsia

Question 10

What is the mechanism of actions of phenicols?

Answer 10

• inhibits peptidyl transferase required for bacterial protein synthesis

Question 11

What drugs are in the phenicols family?

Answer 11

• Chloramphenicol
• Florfenicol

Question 12

Which phenicol can be used safely in production animals and why would we need to use it?

Answer 12

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)

Question 13

What is centiofur effective against?

Answer 13

• Some activity against Gram + ve Aerobes (Streptococci highly susceptible, Enterococci resistant), anaerobes, Penicillinase ‐ producing Staphylococcus
• Good activity against Gram ‐ ve Aerobes (except Enterobacter & Serratia)

Question 14

How does administantion of centiofur differ in dogs and horses and cows?

Answer 14

• 1x injection IM in horses and cows
• Daily sub-cut injections in dogs

Question 15

Is there a withholding period for cows given centiofur?

Answer 15

yes 24-72h

Question 16

What are macrolides effective against?

Answer 16

• Good activity against gram +ve aerobes, anaerobes, penicillinase – producing staphylococcus, Actinobacillus, Brucella, Campylobacter, Pasteurella spp., mycoplasma, chlamydophilia and chlamydia.
• NO activity against enterobacterales

Question 17

What macrolides are used in dogs, cats and people?

Answer 17

• Ezythromycin
• Azithromycin
• Clarithromycin
• Roxithromycin
• Spiramycin (when used with metronidazole)

Question 18

What macrolides are given to production animals?

Answer 18

Tulathromycin, tylosin and tilmicosin

Question 19

What is the mechanism of action of macrolides?

Answer 19

o Inhibits protein synthesis by reversibly binding to 50S ribosome subunit.
o Resulting in premature detachment of incomplete polypeptide chains

Question 20

What are lincosamides effective against?

Answer 20

• Good activity against Many gram + ve aerobes, Anaerobes, Many penicillinase ‐ producing Staphylococcus, Campylobacter jejuni
• NO activity against enterobacterales

Question 21

What drugs are in the lincosamides family?

Answer 21

Clindamycin and lincomycin

Question 22

What is a complication observed in cats given lincosamides?

Answer 22

If administered orally to cats, can result in oesophagela inflammation - needs to be administered with water

Question 23

What is clindamycin used to treat?

Answer 23

Used to treat neospora, toxoplasmosis, anaerobic infections

Question 24

What are the adverse effects seen with lincomycin?

Answer 24

• 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’.