-
Why are gram +ve bacteria more susceptible to penicillins?
Penicillins target the peptidoglycan in bacterial cell walls
There is a large amount of peptidoglycan in the gram +ve wall so more target
There is a very small amount of peptidoglycan in the gram -ve wall which is also surrounded by a membrane, so there is less target and a protective layer for the penicillins to get through
-
Acid labile
- Unstable in gastric acid
- Can't give orally
↑ acidity, ↑ ionisation, ↓ absorption
-
Basic
↓ acidity, ↓ ionisation, ↑ absorption
Ion trapping in milk/udder, prostate, lung, foetus and sites of inflammation
-
Renal Crystalluria
- Urine solubility exceeded
- Principally acetylated metabolites
- Crystallisation greater in acidic urine
- Alkalinisation of urine ↑elimination and ↓precipitation
- May be reduced by:using longer acting compounds
- using more potent drugs
- using combinations of sulphonamides
-
Sulphonamide/Diaminopyrimidine Combinations
- Trimethoprim + sulphadoxine or sulphadiazine
- (5:1)
- Advantages:
- synergistic + bactericidal
- sulphonamide can be used at 1/8 dose
- resistance to combinations is low
-
Florfenicol
Cloramphenicol → thiamphenicol → florfenicol
- Does NOT induce irreversible bone marrow aplasia in humans
- Causes REVERSIBLE haematopoetic depression in animals
- Rapidly absorbed after IM (give to calves every 48hrs)
- Good systemic availability
- Long t½
- ↑Vd
- Some metabolism, rest excreted unchanged in urine
- Broad spectrum
- CALF PNEUMONIA
|
|
