Beta Lactams Flashcards
What is the target of beta-lactams?
Transpeptidase enzyme
It alters the action of transpeptidase, resulting in defective cell wall synthesis. Cell wall is unosmotically active and cell dies.
Microbial resistance to beta-lactams
- Beta-lactamase enzyme
- Hydrolyzes beta-lactam ring - Permeability of cell wall
- Gram neg are impermeable to beta-lactams - Reduced sensitivity of penicillin binding protein
What are penicillin binding proteins
Proteins that link to transpeptidase enzyme
Beta lactams bind to PDPs, interfering with transpeptidase reaction
When are beta lactams effective
Only during rapid growth stage
because cell-wall synthesis occurs in rapidly growing period
What is natural penicillin derived from
Penicillin mold
What spectrum is natural penicillin
Narrow
What improves solubility of penicillin G
Na/K salts
What improves the half-life of penicillin G
Benzathine and Procaine salts
Which natural penicillin is highly inactivated by acidic mediums and thus should only be taken parenteral route
Penicillin G
Which natural penicillin is highly stable in a gastric acid medium
Penicillin V
Which natural penicillin can be taken orally
Penicillin V (acid resistant)
T/F - natural penicillins are good for anerobic infections
TRUE
T/F - natural penicillins are good for gram positive aerobic infection
True
T/F - natural penicillins are effective against gram negative aerobic and anaerobic infections
False! They are only effective against gram + aerobic infections
They are effective against both gram pos/neg anerobes
3 dosage forms of natural penicillin
- Sodium/potassium salt (Crystalline penicillin)
- Procaine penicillin
- Benzathine penicillin
Which form of natural penicillin is long acting
Procaine penicillin
Which form of natural penicillin is good for repositories (IM/intramammary)
Benzathine penicillin
Which penicillins are resistant against pencillinase
Isoxazolyl penicillin (semi-synthetic)
Isoxazolyl penicillins (5)
- Cloxacillin
- Oxacillin
- Dicloxacillin
- Nafcillin
- Methicillin
Which isoxazolyl penicillins have good oral absorption (acid stable)
- Cloxacillin
- Oxacillin
- Dicloxacillin
Which isoxazolyl penicillins have poor oral absoprtion
- Nafcillin
2. Methicillin
Microbial susceptibility of penicillinase resistant penicillins
- Penicillinase producing staph
2. Bacterial infetions of the eye (Staph, Bacillus)
Which are broad spectrum penicillins
Amoxicillin
Ampicillin
Prodrug forms of aminopenicillins (4)
- Bacampicillin
- Hetacillin
- Pivampicillin
- Talampicillin
What are aminopenicillins? Are they sensitive to beta-lactamase?
Broadspectrum penicillins
Beta-lactamase sensitive
Microbial susceptibility of broad spectrum penicillin
All microbes susceptible to natural penicillin
Enterobactericae (gram negs like E. coli, Proteus, Salmonella)
What should broad spectrum penicillins be given with
Beta-lactamase inhibitors
What are Extended Spectrum penicillins effective against
Gram neg aerobes/anerobes
Enterobacteriacea
Bacteriodes
PSEUDOMONAS!
Extended spectrum penicillins (5)
CAMP-T
- Carbenicillin
- Azocillin
- Mezlocillin
- Pipercillin
- Ticarcillin
What should extended penicillins be given with
Beta-lactamase inhibitors
Which aminopenicillin has greater bioavailability
Amoxicillin
Because it is more acid stable —> complete absorption
How should procaine penicillin G NEVER be administered
IV route – affects cardiac conduction system
How should Benzathine penicillin G be administered? Why?
IM because its a repository
What prolongs penicillin absoprtion by 18h?
Suspension in oil
Where are penicillins mainly distributed to
ECF
T/F - penicillins have wide distribution, including to CSF, aqueous humor and synovial fluid
False - does not penetrate these structures
Which group of penicillins permeates more through cell membrane?
Semi-synthetics
T/F - lots of penicillin is excreted in milk?
True - because the milk:plasma equilibrium concentration ratio is 1:5, meaning it is distributed in milk in lactating animals
