Flashcards in Antibiotics - Pencillins and Cephalosporins Deck (133)
what does Penicillin, Cephalosporin, Monobactam, Carbapenem have in common?
ß lactam ring
Penicillin, Cephalosporin, Monobactam, Carbapenem all have a common function:
inhibiting cell wall synthesis
in general, how are Penicillin, Cephalosporin, Monobactam, Carbapenem inactivated?
ß lactamase enzymes - cleave the ß-lactam ring
Why do carbapenems additional stability (more resistant to ß lactamases) over the rest of the drugs?
the H next to the keto group is oriented ABOVE the plane, and this configuration seems to stabilize the molecule, and make it more resistant to ß-lactamases (others: below)
What type of hypersensitivity reaction does penicillin usually cause?What type of physical manifestations?
IgE Type I Hypersensitivity
(rash, hives, angioedema, anaphylaxis).
If one is severely allergic to penicillin, what other drugs are they likely to be allergic too as well?
Cephalosporin, Monobactam, Carbapenem
Which one is the safest to use if if the patient had a mild allergic reaction? Why?
monobactam, since it looks the least like penicillin (it doesn’t have the second ring) and is least likely to trigger IgE compared to the other ones
Structure of penicillin?
all contain Ring A (thiazolidine ring) attached to Ring B (ß-lactam ring)
MoA of penicillin?
bind covalently to Penicillin-binding proteins (PBP’s) at the active site, thereby interfering with the transpeptidase reaction
how does resistance develop against penicillin?
1) Inactivation by ß-lactamase
2) Modification of target PBP
3) Impaired penetration of the cell (ex: ∆ porin channel)
4) Presence of a new efflux pump
how does MRSA develop?
Modification of target PBP
What drugs are in the Benzopenicillin class?
sensitivity of penicillin G to ß lactamases?
How is Penicillin G administered?
parenteral (poor oral bioavailability)
Procaine suspn (IM); duration 1-2 days
* Benzathine suspn (IV); duration 1-4 wks; great for kids
How is Penicillin V administered?
PO; very stable in stomach acid
Penicillins are effective in treating these bugs
* strep. pneumo
* S. pyogenes
* N. meningitides
* Spirochetes (T. pallidum)
what bugs are resistant to penicillin?
Staph (>85%)Pneumococcus (10-30%)bowel anaerobesgonorrhea (Pen G)most GNR’s
Contraindications of penicillin?
Side Effects of penicillins?
1) drug allergy especially rash, anaphylaxis
2) anemia (binds to RBC and induces hemolysis
3) Seizures following high doses
Drug interactions with penicillins?
* synergy with gentamicin against staph and enterococcus
* probenecid inhibits renal active tubular secretion
What situations would warrant penicillin treatment?
1. Streptococcal pharyngitis and skin infections
4. Endocarditis - if organism is sensitive
5. Dental infection (by microaerophilic streptococcus)
7. Prevent rheumatic fever (GrpA ß hemolytic strep complication)
Drugs in the Aminopenicillins class?
sensitivity of aminopenicillins to ß lactamases?
sensitive (its nearly identical to penicillin)
mechanism of action of aminopenicillins?
binds PBP’s and inhibits the assembly of the bacterial cell wall, bactericidal
How is ampicillin different than amoxicillin?
Ampicillin - PO or IV
Amoxicillin - PO (higher oral bioavailability) - newer version of ampicillin with slightly wider spectrum of action; less likely to cause diarrhea
what bugs are sensitive to aminopenicillins?
extended spectrum of action
* Haemophilus influenza
* E. coli
* Listeria monocytogenes
* Proteus mirabilis
Amp HELPSS to kill enterococci
What bugs are resistant to aminopenicillins?
* most staph
* some pneumococcus (>30%)
* some H. flu
* bowel anaerobes
* some GNRs
SE of aminopenicillins?
* drug allergy especially rash, anaphylaxis
* seizures following high doses
* antibiotic-associated colitis
Contraindications of aminopenicillins?