mechanism of action of penicillins - ✔✔ drugs that weaken the bacterial cell wall; penicillins contain a B-lactam ring which weakens the cell wall
... [Show More] by binding to Penicillin binding proteins (PBPs)
targets of penicillins in the cell wall - ✔✔ 1. binding to penicillin binding proteins
2. inhibition of transpeptidases (enzymes that form cross-bridges between polymer strands to form the bacterial cell wall)
3. activation of autolysins (promote the active destruction of the cell wall)
basic penicillin chemical structure - ✔✔
effect of penicillin's inhibition of transpeptidase - ✔✔ -The bacterial cell wall is composed of long strands of a peptidoglycan polymer.
-Transpeptidase enzymes create cross-bridges between the peptidoglycan strands, giving the cell wall its strength.
-By inhibiting transpeptidases, penicillins prevent cross-bridge synthesis, weaken the cell wall, and make the bacterium susceptible to osmotic lysis
gram-positive vs. gram-negative cell walls - ✔✔ The Gram(+) cell wall lacks an outer membrane. The outer membrane of the Gram(-) cell envelope prevents certain pencillins from reaching transpeptidase and other penicillin-binding target molecules.
Are penicillins more effective in treating gram-negative or gram-positive bacteria? - ✔✔ gram-positive bacteria because they lack the outer membrane of gram-negative which present penicillins from reaching the cell wall
function of B-lactamase activity - ✔✔ breaks B-lactam ring (leaving the penicillin ineffective)
penicillin activity - ✔✔ 1. most Gram(+) bacteria (except for penicillinase producing Staphylococci)
2. Gram(+) cocci- Streptococcus pneumoniae (pneumonia and meningitis) and Streptococcus viridans (infectious endocarditis)
3. Gram(+) bacilli- Clostridium perfringens (gangrene), Clostridium tetani (tetanus), and Bacillus anthracis (anthrax)
4. Gram(-) cocci-Neisseria meningitidis (meningitis) and non-penicillinase-producing strains of N. gonorrhoeae (gonorrhea)
5. Gram(-) spirochete- Treponema pallidum (syphilis)
penicillin G - ✔✔ -The prototype drug of the narrow-spectrum penicillins (penicillinase sensitive)
-Unstable in acid
-Given IM
-When high blood levels are needed it can be given by IV.
characteristics of penicillin V - ✔✔ can be given orally since it is stable in acid with a short half-life
What determines the unique structure of each penicillin? - ✔✔ The unique structure of individual penicillins is determined by the side chain coupled to the penicillin nucleus at the R position. This side chain influences acid stability, pharmacokinetic properties, penicillinase resistance, and ability to bind specific penicillin-binding proteins.
beta-lactase inhibitors - ✔✔ Drugs that inhibit bacterial beta-lactamases. When combined with penicillinase-sensitive penicillin, the antimicrobial spectrum of these drugs is extended
example of combined penicillinase-sensitive penicillin and beta-lacamase inhibitors - ✔✔ ampicillin + sulbactam = [Unasyn]
amoxicillin + clavulanic acid = [Augmentin]
ticarcillin + clavulanic acid = [Timentin]
piperacillin + tazobactam = [Zosyn]
ceftazidime + avibactam = [Avycaz]
side effects of penicillin - ✔✔ -allergic reaction
-GI disturbances (supra infections)
other penicillin alternatives if allergic to penicillins - ✔✔ -cephalosporin (1% cross-allergic reaction)
-vancomycin
-erythromycin
-clindamycin
penicillin drug-drug interactions - ✔✔ 1. aminoglycosides
2. oral contraceptives
3. probenecid
4. tetracyclines
penicillin + aminoglycoside drug-drug interaction - ✔✔ may be synergistic against selected organisms [Show Less]